Efficacy of a continuous, multiagent chemotherapeutic protocol versus a short-term single-agent protocol in dogs with lymphoma

Daniela Simon Departments of Small Animal Medicine and Surgery, University of Veterinary Medicine Hannover, 30173 Hannover, Germany.

Search for other papers by Daniela Simon in
Current site
Google Scholar
PubMed
Close
 Dr med vet
,
Sol Naranjo Moreno Departments of Small Animal Medicine and Surgery, University of Veterinary Medicine Hannover, 30173 Hannover, Germany.

Search for other papers by Sol Naranjo Moreno in
Current site
Google Scholar
PubMed
Close
 Dr med vet
,
Johannes Hirschberger Small Animal Medical Clinic, Veterinary Faculty, Ludwig-Maximilians University Munich, 80539 Munich, Germany.

Search for other papers by Johannes Hirschberger in
Current site
Google Scholar
PubMed
Close
 Dr med vet, Dr habil
,
Andreas Moritz Small Animal Medical Clinic, Veterinary Faculty, Justus-Liebig University Giessen, 35392 Giessen, Germany.

Search for other papers by Andreas Moritz in
Current site
Google Scholar
PubMed
Close
 Dr med vet, Dr habil
,
Barbara Kohn Small Animal Clinic, Veterinary Faculty, Free University Berlin, 14163 Berlin, Germany.

Search for other papers by Barbara Kohn in
Current site
Google Scholar
PubMed
Close
 Dr med vet, Dr habil
,
Stephan Neumann Clinic for Small Animals, Institute for Veterinary Medicine, University of Göttingen, 37077 Göttingen, Germany.

Search for other papers by Stephan Neumann in
Current site
Google Scholar
PubMed
Close
 Dr med vet
,
Konrad Jurina Small Animal Clinic, Veterinary Faculty, University of Leipzig, 04103 Leipzig, Germany.

Search for other papers by Konrad Jurina in
Current site
Google Scholar
PubMed
Close
 Dr med vet
,
Stefan Scharvogel Small Animal Clinic, Veterinary Faculty, University of Leipzig, 04103 Leipzig, Germany.

Search for other papers by Stefan Scharvogel in
Current site
Google Scholar
PubMed
Close
 Dr med vet
,
Claudia Schwedes Small Animal Clinic Augsburg, Klinkerberg 1-3, 86152 Augsburg, Germany.

Search for other papers by Claudia Schwedes in
Current site
Google Scholar
PubMed
Close
 Dr med vet
,
Manfred Reinacher Department for Pathology, Veterinary Faculty, Justus-Liebig University Giessen, 35392 Giessen, Germany.

Search for other papers by Manfred Reinacher in
Current site
Google Scholar
PubMed
Close
 Dr med vet
,
Martin Beyerbach Departments of Biometry, Epidemiology, and Information Processing, University of Veterinary Medicine Hannover, 30173 Hannover, Germany.

Search for other papers by Martin Beyerbach in
Current site
Google Scholar
PubMed
Close
 Dr med vet
, and
Ingo Nolte Departments of Small Animal Medicine and Surgery, University of Veterinary Medicine Hannover, 30173 Hannover, Germany.

Search for other papers by Ingo Nolte in
Current site
Google Scholar
PubMed
Close
 Dr med vet, Dr habil

Abstract

Objective—To compare response rates and remission and survival times in dogs with lymphoma treated with a continuous, multiagent, doxorubicin-based chemotherapeutic protocol or with a short-term single-agent protocol incorporating doxorubicin.

Design—Nonrandomized controlled clinical trial.

Animals—114 dogs with lymphoma.

Procedures—Dogs were treated with a chemotherapeutic protocol consisting of L-asparaginase, vincristine, cyclophosphamide, doxorubicin, methotrexate, and prednisolone (n = 87) or doxorubicin alone (27).

Results—63 of 86 (73%) dogs treated with the multiagent protocol (data on response was unavailable for 1 dog) and 14 of 27 (52%) dogs treated with the single-agent protocol had a complete remission. Dogs with lymphoma classified as substage ≤ and dogs with a high BUN concentration at the time of initial diagnosis were significantly less likely to have a complete remission. No significant difference in remission or survival time could be demonstrated between treatment groups. Incidence of hematologic and gastrointestinal tract toxicoses did not differ between treatment groups, with the exception that vomiting was more common among dogs treated with the multiagent protocol.

Conclusions and Clinical Relevance—In this population of dogs, we were not able to identify any significant difference in remission or survival times between dogs with lymphoma treated with a continuous, multiagent chemotherapeutic protocol and dogs treated with a short-term single-agent protocol involving doxorubicin.

Abstract

Objective—To compare response rates and remission and survival times in dogs with lymphoma treated with a continuous, multiagent, doxorubicin-based chemotherapeutic protocol or with a short-term single-agent protocol incorporating doxorubicin.

Design—Nonrandomized controlled clinical trial.

Animals—114 dogs with lymphoma.

Procedures—Dogs were treated with a chemotherapeutic protocol consisting of L-asparaginase, vincristine, cyclophosphamide, doxorubicin, methotrexate, and prednisolone (n = 87) or doxorubicin alone (27).

Results—63 of 86 (73%) dogs treated with the multiagent protocol (data on response was unavailable for 1 dog) and 14 of 27 (52%) dogs treated with the single-agent protocol had a complete remission. Dogs with lymphoma classified as substage ≤ and dogs with a high BUN concentration at the time of initial diagnosis were significantly less likely to have a complete remission. No significant difference in remission or survival time could be demonstrated between treatment groups. Incidence of hematologic and gastrointestinal tract toxicoses did not differ between treatment groups, with the exception that vomiting was more common among dogs treated with the multiagent protocol.

Conclusions and Clinical Relevance—In this population of dogs, we were not able to identify any significant difference in remission or survival times between dogs with lymphoma treated with a continuous, multiagent chemotherapeutic protocol and dogs treated with a short-term single-agent protocol involving doxorubicin.

Malignant lymphoma is one of the most common neoplastic diseases in dogs with an annual incidence of up to 24 cases per 100,000 dogs in older studies and an incidence of 114 cases per 100,000 dogs in a more recent study.1–3 Treatment with chemotherapeutic protocols consisting of an induction phase and a prolonged maintenance phase has resulted in remission rates as high as 94% and remission times of approximately 1 year.4–6 On the other hand, treatment with doxorubicin as a single agent has been reported to result in response rates of 59% to 85% with remission times of up to 7 months,7–9 and in a previous study,10 efficacy of a combination protocol involving continuous administration of cyclophosphamide, vincristine, and prednisone was similar to efficacy of doxorubicin administered as a single-agent protocol. In addition, good treatment outcomes have recently been reported for multiagent protocols that do not include a maintenance phase.11–15 Remission and survival times attained with these protocols were reported to be comparable to those obtained with long-term, continuous chemotherapeutic protocols.12–14 These reports suggest that as is the case for treatment of non-Hodgkin's lymphoma in human patients,16 maintenance chemotherapy may not be necessary to attain long remission and survival times in dogs with lymphoma. However, whether the efficacy of short-term treatment with doxorubicin as a single agent is comparable to the efficacy of standard continuous, multiagent chemotherapeutic protocols has not been determined.

Therefore, the purpose of the study reported here was to compare response rates and remission and survival times in dogs with lymphoma treated with a continuous, multiagent, doxorubicin-based chemotherapeutic protocol or with a short-term single-agent protocol incorporating doxorubicin.

Materials and Methods

Dogs—Dogs evaluated at any of the participating institutions between March 1996 and November 2000 in which a diagnosis of malignant lymphoma had been confirmed on the basis of results of histologic or cytologic evaluation were eligible for enrollment in the study. In addition, dogs were included only if they were free from any other serious medical conditions that could have limited full compliance with the study protocol and the owner provided signed consent.

Pretreatment evaluation—All dogs underwent a complete pretreatment evaluation consisting of a physical examination, CBC, serum biochemical panel, urinalysis, thoracic and abdominal radiography, abdominal ultrasonography, and electrocardiography. Echocardiography was performed if indicated on the basis of abnormalities detected during thoracic auscultation, radiography, or electrocardiography. A bone marrow aspirate was obtained and submitted for cytologic evaluation if indicated on the basis of results of the CBC. Tumors were measured directly with calipers or on radiographic or ultrasonographic images. Clinical staging was performed in accordance with the World Health Organization's clinical staging system for lymphoma in domestic animals.17 Immunophenotyping was performed in a subset of patients by means of immunohistochemical staining with CD3 and CD79a markers or by means of fluorescent-activated cell-sorting analysisa of a lymph node aspirate.18

Treatment and monitoring—Dogs were treated, on the basis of owner preference, with a continuous, multiagent chemotherapeutic protocol incorporating L-asparaginase, vincristine, cyclophosphamide, doxorubicin, methotrexate, and prednisolone (Appendix) or with a short-term single-agent protocol that involved administration of doxorubicin (30 mg/m2 given as an IV infusion over 30 minutes) every 3 weeks for 5 consecutive treatments. For dogs in the single-agent treatment group, a CBC was performed prior to each doxorubicin treatment. For dogs in both treatment groups, dexamethasone (0.5 mg/kg [0.23 mg/lb], IV) was given before administration of L-asparaginase or doxorubicin, and electrocardiography, along with echocardiography if indicated on the basis of electrocardiographic or auscultatory abnormalities, was performed prior to each doxorubicin treatment. Owners of dogs in the multiagent treatment group were instructed to administer furosemide for 2 days and to frequently walk their dogs after administration of cyclophosphamide.

Serum biochemical analyses were performed when dogs developed any signs of toxicosis or other signs of concern to the attending clinician. Tumor size was evaluated at each visit by direct measurement or measurement on radiographic or ultrasonographic images. In the case of a relapse, patients in the multiagent treatment group were given a second cycle of the induction protocol and patients in the single-agent treatment group were treated with the multiagent protocol. Follow-up examinations following completion of the initial treatment were scheduled monthly during the first 3 months, every 6 weeks for the subsequent 3 months, and every 3 months thereafter.

Response assessment—In evaluating response to treatment, complete remission was defined as a 100% reduction in size of all measurable disease; partial remission was defined as a > 50% but < 100% reduction in size of all measurable disease; stable disease was defined as a < 50% reduction in size of all measurable disease, no change in size, or < 25% increase in size of all measurable disease; and progressive disease was defined as a > 25% increase in size of all measurable disease or the appearance of new lesions. All responses were required to last for at least 14 days. Remissions of shorter duration were classified as stable disease.

Assessment of toxicoses—Hematologic and gastrointestinal tract toxicoses were evaluated 1 week after each treatment. Neutropenia was graded according to criteria established by the Veterinary Co-Operative Oncology Group.19 Gastrointestinal tract toxicoses were graded from 0 to 4 (grade 0 = no evidence of gastrointestinal tract toxicosis; grade 1 = inappetence, anorexia, vomiting, or diarrhea that was transient or responsive to dietary management; grade 2 = inappetence, vomiting, or diarrhea necessitating medical treatment; grade 3 = inappetence, vomiting, or diarrhea necessitating medical treatment and postponement of the subsequent chemotherapy treatment; and grade 4 = inappetence, vomiting, or diarrhea necessitating medical treatment, postponement of the subsequent chemotherapy treatment, and hospitalization) as described.15 Other signs of toxicosis such as hemorrhagic cystitis or fever were recorded.

Statistical analysis—Complete and partial remission rates were defined as number of dogs with a complete or partial remission divided by the total number of dogs treated. Kaplan-Meier product-limit analysis was used for analysis of remission and survival times. A complete event was defined as lymphoma relapse or death, respectively. Dogs were censored if they were alive at the time of data analysis (survival analysis) and were still in remission at the time of data analysis or death (remission analysis).

The Kaplan-Meier log-rank test was used to compare remission and survival times between the 2 treatment groups. The Fisher exact test was used to compare remission rates between the 2 treatment groups. The Mann-Whitney U test was used to compare age and body weight between treatment groups. The Fisher exact test was used to compare distributions for sex, clinical stage, substage, anatomic classification, and immunophenotype between treatment groups.

Multivariate Cox forward regression analysis was used to evaluate the following variables for their independent association with remission and survival times: sex, body weight, age, clinical stage, substage, anatomic classification (multicentric vs other), corticosteroid pretreatment, immunophenotype, treatment group, serum creatinine concentration at the time of diagnosis (ie, serum creatinine concentration greater than the upper reference limit of 1.2 mg/dL), high BUN concentration at the time of diagnosis (BUN concentration > 50 mg/dL), hypercalcemia at the time of diagnosis (serum calcium concentration > 2.87 mmol/L or serum ionized calcium concentration > 1.47 mmol/L), anemia at the time of diagnosis (Hct < 40%), and thrombocytopenia at the time of diagnosis (platelet count < 150,000 platelets/ML). Multivariate logistic regression was used to determine whether these factors were associated with the likelihood that dogs would have a complete remission.

All statistical analyses were performed with standard software.b Values of P < 0.05 were considered significant.

Results

Patient population—A total of 114 dogs were enrolled in the study. Of these, 24 were of mixed breeding, and the remaining 90 represented 37 breeds. Breeds represented by ≥ 4 individuals included German Shepherd Dog (n = 11), Bernese Mountain Dog (10), Rottweiler (8), Airedale Terrier (5), Münsterländer (5), Doberman Pinscher (4), and Schnauzer (4).

Median age was 7 years (range, 1 to 14 years), and median body weight was 32 kg (70.4 lb; range, 4 to 69 kg [8.8 to 151.8 lb]). There were 54 females (24 spayed) and 60 males (12 castrated). Seventy-six of the 114 (67%) dogs had not received any previous treatment. Thirty-eight (33%) dogs had previously been treated with corticosteroids.

Clinical staging—Three of the 114 (2.6%) dogs were classified as stage 1, 3 (2.6%) were classified as stage 2, 38 (33.3%) were classified as stage 3, 37 (32.5%) were classified as stage 4, and 33 (29%) were classified as stage 5. Fifty (43.9%) dogs were substage a, and 64 (56.2%) were substage b. Sixteen of the 38 (42%) dogs with stage 3 lymphoma, 22 of the 37 (59%) dogs with stage 4 lymphoma, and 24 of the 33 (73%) dogs with stage 5 lymphoma were classified as substage b. One hundred six of the 114 (93%) dogs had multicentric lymphoma, 5 (4.4%) had intestinal lymphoma, and 1 each had mediastinal, cutaneous, and nasal lymphoma. Bone marrow aspirates from 64 dogs were submitted for cytologic examination, and 19 of the 64 (30%) had evidence of bone marrow involvement.

Laboratory findings—Thirty-three of the 114 (29%) dogs had anemia at the time of initial examination, and 34 (30%) had thrombocytopenia. Fourteen (12.3%) dogs had hypercalcemia, and 22 (19%) had a high BUN concentration. Fourteen of the dogs with high BUN concentration were treated with the multiagent protocol, and 8 were treated with the single-agent protocol.

Immunophenotyping—Immunophenotyping was performed in 53 dogs. Of these, 44 (83%) had the B-cell phenotype and 9 (17%) had the T-cell phenotype. Of the 9 dogs with T-cell lymphoma, 7 had hypercalcemia and 2 had normocalcemia.

Comparison of treatment groups—Eighty-seven (76%) of the dogs were treated with the multiagent protocol, and 27 (24%) were treated with the single-agent protocol. Median body weight of dogs in the multiagent treatment group (30.5 kg [67.1 lb]; range, 4 to 69 kg [8.8 to 151.8 lb]) was not significantly (P = 0.068) different from median body weight of dogs in the single-agent treatment group (34 kg [74.8 lb]; range, 6 to 45 kg [13.2 to 99 lb]). However, dogs in the multiagent treatment group were significantly (P = 0.041) older (median, 7 years; range, 2 to 14 years) than dogs in the single-agent treatment group (median, 5 years; range, 1 to 13 years). Distributions for sex, clinical stage, substage, anatomic classification, and immunophenotype were not significantly different between groups (Table 1).

Table 1—

Charateristics of dogs enrolled in a study comparing response rates and remission and survival times in dogs with lymphoma treated with a continous, multigent, doxorubicin-based chemotherapeutic protocol (n = 87) or with a short-term single-agent protocol incorporating doxorubicin (27).

VariableMultiagent protocolSingle-agent protocolP value
Sex0.14
Female3915
Male4812
Tumor clinical stage0.63
130
230
32612
4289
5276
Tumor substage0.66
a3713
b5014
Tumor classification0.19
Multicentric7927
Intestinal50
Other*30
Tumor immunophenotype0.71
B-cell2915
T-cell54
Previous treatment with corticosteroids0.82
Yes308
No5719
Anemia at diagnosis0.43
Yes267
No6120
Thrombocytopenia at diagnosis0.57
Yes258
No6219
Hypercalcemia at diagnosis0.09
Yes86
No7921

Data are given as number of dogs.

Mediastinal, cutaneous, and nasal (1 each).

Immunopheno-typing was performed in only 53 dogs.

Treatment response—One dog treated with the multiagent protocol was lost to follow-up following induction chemotherapy, and no information on treatment response was available. Therefore, this dog was excluded from further analyses.

Of the 86 dogs treated with the multiagent protocol, 63 (73%) had a complete remission, 15 (17%) had a partial remission, and 8 (9%) had stable or progressive disease (ie, no response). Of the 27 dogs treated with the single-agent protocol, 14 (52%) had a complete remission, 6 (22%) had a partial remission, and 7 (26%) had stable or progressive disease. Response distribution was not significantly (P = 0.06) different between treatment groups.

Of the variables examined in the multivariate regression analysis, only substage (P = 0.005) and high BUN concentration (P = 0.004) had significant independent associations with the likelihood that dogs would have a complete remission, with dogs classified as substage ≤ and dogs with a high BUN concentration at the time of initial diagnosis less likely to have a complete remission.

Response after relapse—Thirty-three dogs (27 in the multiagent treatment group and 6 in the single-agent treatment group) that had a relapse received a second round of chemotherapy consisting of the multiagent chemotherapeutic protocol. Response information was available for 31 of the 33 dogs, of which 14 (45%) had a complete remission, 9 (29%) had a partial remission, and 8 (26%) had no response (ie, stable or progressive disease). There was no significant (P = 0.56) difference in response rates between groups when dogs were grouped on the basis of initial treatment group.

First remission duration—Median follow-up time from initial diagnosis was 150 days (range, 3 to 1,669 days; 95% confidence interval, 124 to 176 days).

For dogs treated with the multiagent protocol that had a complete remission (n = 63), median complete remission time was 204 days (range, 19 to 1,669 days) and 6-month, 1-year, and 2-year complete remission rates were 57%, 39%, and 21%, respectively. For dogs treated with the single-agent protocol that had a complete remission (n = 14), median complete remission time was 309 days (range, 105 to 475 days), and 6-month and 1-year complete remission rates were 77% and 19%, respectively. We did not detect a significant (P = 0.63) difference between groups in regard to complete remission time (Figure 1). In this subset of 77 dogs that had a complete remission, Cox regression analysis did not identify any patient variables significantly associated with duration of complete remission.

Figure 1—
Figure 1—

Kaplan-Meier curves of remission times for dogs with lymphoma that had a complete remission following treatment with a continuous, multiagent chemotherapeutic protocol (n = 63; solid line) or a single-agent protocol involving doxorubicin (14; dotted line). Groups were not significantly (P = 0.63) different.

Citation: Journal of the American Veterinary Medical Association 232, 6; 10.2460/javma.232.6.879

For dogs treated with the multiagent protocol that had a partial remission (n = 15), median partial remission time was 142 days, and for dogs treated with the single-agent protocol that had a partial remission (6), median partial remission duration was 158 days. No significant (P = 0.84) difference was found between these groups.

Survival—Median overall survival time for dogs treated with the multiagent protocol (n = 86) was 251 days (range, 3 to 1,669 days), and 6-month, 1-year, and 2-year survival rates were 63%, 35%, and 20%, respectively. Median overall survival time for dogs treated with the single-agent protocol (n = 27) was 322 days (range, 5 to 475 days), and 6-month, 1-year, and 2-year survival rates were 60%, 20%, and 0%, respectively. We did not detect a significant (P = 0.38) difference between treatment groups with regard to overall survival time. In the multivariate analysis, substage (P = 0.012) and immunophenotype (P = 0.02) were significantly associated with overall survival time, with dogs with substage a and dogs with the B-cell phenotype having longer survival times.

Median survival time for the 77 dogs with a complete remission was 352 days (range, 19 to 1,669 days). For dogs treated with the multiagent protocol that had a complete remission (n = 63), median survival time was 322 days (range, 19 to 1,669 days), and 6-month, 1-year, and 2-year survival rates were 73%, 43%, and 26%, respectively. For dogs treated with the single-agent protocol that had a complete remission (n = 14), median survival time was 352 days (range, 91 to 475 days), and 6-month, 1-year, and 2-year survival rates were 85%, 31%, and 0%, respectively. We did not detect a significant (P = 0.88) difference between groups in regard to overall survival time (Figure 2). In this subset of dogs, Cox regression analysis did not identify any patient variables significantly associated with survival time.

Figure 2—
Figure 2—

Kaplan-Meier curves of survival times for dogs with lymphoma that had a complete remission following treatment with a continuous, multiagent chemotherapeutic protocol (n = 63; solid line) or a single-agent protocol involving doxorubicin (14; dotted line). Groups were not significantly (P = 0.88) different.

Citation: Journal of the American Veterinary Medical Association 232, 6; 10.2460/javma.232.6.879

Median overall survival time for the 21 dogs with a partial remission was 196 days (range, 18 to 476 days). Median survival time for dogs treated with the multiagent protocol (196 days) was not significantly (P = 0.92) different from median survival time for dogs treated with the single-agent protocol (160 days).

Toxicoses—Sixty-nine episodes of neutropenia were documented; 58 episodes occurred in dogs treated with the multiagent protocol, and 11 episodes occurred in dogs treated with the single-agent protocol. Of the 69 episodes of neutropenia, 37 (53%) were grade I, 18 (26%) were grade II, and 14 (20%) were grade III. There was no significant (P = 0.15) difference in the occurrence of neutropenia between the 2 treatment groups.

Fifty-nine episodes of vomiting were documented, of which 52 occurred in dogs treated with the multiagent protocol, and 7 occurred in dogs treated with the single-agent protocol. Of the 59 episodes of vomiting, 27 (49%) were grade 1, 18 (30%) were grade 2, 7 (12%) were grade 3, and 7 (12%) were grade 4. Vomiting occurred significantly (P = 0.022) more frequently in dogs in the multiagent treatment group than in dogs in the single-agent treatment group.

Forty-eight episodes of diarrhea were documented, of which 42 occurred in dogs treated with the multiagent protocol, and 6 occurred in dogs treated with the single-agent protocol. Of the 48 episodes of diarrhea, 23 (48%) were grade 1, 11 (23%) were grade 2, 9 (19%) were grade 3, and 5 (10%) were grade 4. There was no significant (P = 0.051) difference in the occurrence of diarrhea between the 2 treatment groups.

Hemorrhagic cystitis was diagnosed in 8 (9%) dogs, all of which were treated with the multiagent protocol. One dog treated with the multiagent protocol was suspected to have developed neurotoxicosis following vincristine administration. One dog treated with the multiagent protocol died during induction treatment secondary to pyometra, peritonitis, and sepsis.

Discussion

In the present study, we were not able to identify any significant difference in remission or survival times between dogs with lymphoma treated with a continuous, multiagent chemotherapeutic protocol and dogs treated with a short-term single-agent protocol involving doxorubicin. In addition, we were not able to identify any significant difference in the distribution of response rates between treatment groups, although the P value was close to our cutoff for significance. Our results are similar to those of a previous study10 in which efficacy of doxorubicin administered as a single-agent protocol was similar to efficacy of a combination protocol involving continuous administration of cyclophosphamide, vincristine, and prednisone. Our results may also support results of previous studies11–15 in which patients receiving short-term chemotherapy had outcomes comparable to those associated with long-term regimens.

A preference in using the combination regime does, however, persist on the authors' side. This subjective preference is partly based on the observation that although no statistical difference could be demonstrated in the present study, dogs receiving the multiagent protocol had 2-year remission and survival probability rates of 21% and 26%, respectively. Additionally, single-agent protocols are in general thought to lead to a more rapid induction of drug resistance. Thus, one could hypothesize that the addition of supplementary drugs to a doxorubicin protocol would result in better treatment outcome.20 Considering these aspects, a multiagent protocol may subjectively be perceived as being advantageous in comparison to a single-agent doxorubicin regime; this, however, remains speculative until future studies demonstrate a statistical difference.

Importantly, in the present study, although we did not find significant differences in median remission and survival times between treatment groups, the short median follow-up time (150 days) and the high rate of censoring may have limited our ability to detect a true difference between groups. Therefore, additional trials with longer follow-up times are needed to verify our findings concerning long-term outcome following treatment and to verify whether the efficacy of the single-agent protocol is indeed equivalent to efficacy of the multiagent protocol.

In the present study, substage and immunophenotype were significantly associated with overall survival time, with dogs with substage a and dogs with the B-cell phenotype having longer survival times. This is in accordance with results of previous studies4,15,20-24 and reinforces the notion that dogs with lymphoma that have clinical signs or the T-cell phenotype have a poorer prognosis. Interestingly, substage and BUN concentration at the time of initial diagnosis were independently associated with the likelihood that a dog would have a complete remission, with dogs classified as substage ≤ and dogs with a high BUN concentration at the time of initial diagnosis less likely to have a complete remission. Although substage has previously been shown to negatively influence the probability for complete remission,15,20,21,23 to our knowledge, BUN concentration has not previously been described as an independent prognostic factor for dogs with lymphoma. The reasons for the negative association between BUN concentration and likelihood of a complete remission remain unclear. However, this characteristic may only represent a variation of the finding that dogs with more advanced disease that are sick have a poorer prognosis.13

The present study had several limitations that may restrict the validity of our findings. Two of the most important limitations were that dogs were not randomly assigned to treatment groups and that owners and attending clinicians were not blinded to which treatment was being administered. Dogs were assigned to treatment groups on the basis of owner decision, and this may have led to some degree of bias. Many factors can affect an owner's choice of whether to pursue treatment or which treatment to chose, such as perceived prognosis and financial and logistical considerations. This allocation scheme led to an uneven distribution of patient numbers in the 2 treatment groups, which may have limited our ability to detect differences between groups. On the other hand, statistical analysis of patient variables and clinical stage, substage, and immunophenotype did not reveal any differences between the 2 populations. Moreover, diagnostic and staging procedures were identical for dogs in the 2 groups. Only age differed between treatment groups, with dogs treated with the single-agent protocol being slightly younger. This may have exerted a positive influence on remission or survival time for dogs in this treatment group; however, the extent of this remains unclear.

Another important limitation of the present study was that results of immunophenotyping were available for only approximately half the patients. The immunophenotype is of known prognostic importance, with prognosis better for dogs with the B-cell phenotype than for dogs with the T-cell phenotype.15,20,21 Although there was no difference in phenotype distribution between treatment groups in the present study, the fact that immunophenotype was unknown for a large subset of patients may have introduced some bias.

Finally, it is possible that the number of patients included in the present study was insufficient to demonstrate a significant difference in efficacy between treatment groups. A higher number of cases and an even distribution of cases between groups may have led to the detection of differences in remission and survival times. Retrospective power calculations revealed low power (14%) and showed that 82 patients would have been needed in each group to be 90% certain of detecting a 50% improvement in survival time between groups. To be 90% certain of detecting a 30% improvement in survival time between groups, it would have been necessary to enroll 227 dogs in each treatment group, and it is difficult to accrue these case numbers in veterinary clinical research, even when performing multi-institutional studies.

Interestingly, dogs in the present study treated with the multiagent protocol that had a complete remission had a median remission time of only 204 days, which was substantially less than remission times of 252, 282, and 300 days and 55 weeks reported in previous studies.5,6,12,14 On the other hand, remission and survival times in the present study were comparable to those reported with other protocols.4,7,9,11,22,25-27

It is possible that the inclusion of dogs with nonmulticentric lymphoma in the present study may have contributed to shorter remission times, even though Cox regression analysis did not reveal any significant association between anatomic classification and outcome. Additionally, the present population may have differed from populations described in North American studies (eg, neuter status, breed distribution, or substage distribution), which may have contributed to differences in response duration. For these reasons, results of comparison between the 2 treatment protocols in the present study must be interpreted carefully. Furthermore, the external validity of a clinical trial is subject to limitations associated with a number of factors, such as selection bias and population differences.28,29 These limitations must be taken into consideration when extrapolating results of a study group to the general population.28,29

a.

FACS Calibur, Becton-Dickinson, Heidelberg, Germany.

b.

SPSS, version 11.5, SPSS Inc, Chicago, Ill.

References

  • 1.

    Dorn CR, Taylor DO, Schneider R, et al. Survey of animal neoplasms in Alameda and Contra Costa Counties, California. II. Cancer morbidity in dogs and cats from Alameda County. J Natl Cancer Inst 1968;40:307318.

    • Search Google Scholar
    • Export Citation
  • 2.

    Dorn CR, Taylor DO, Schneider R. The epidemiology of canine leukaemia and lymphoma. Bibl Haematol 1970;36:403415.

  • 3.

    Dobson JM, Samuel S, Milstein H, et al. Canine neoplasia in the UK: estimates of incidence rates from a population of insured dogs. J Small Anim Pract 2002;43:240246.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4.

    Greenlee PG, Filippa DA, Quimby FW, et al. Lymphomas in dogs. A morphologic, immunologic, and clinical study. Cancer 1990;66:480490.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5.

    Keller ET, MacEwen EG, Rosenthal RC, et al. Evaluation of prognostic factors and sequential combination chemotherapy with doxorubicin for canine lymphoma. J Vet Intern Med 1993;7:289295.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6.

    Zemann BI, Moore AS, Rand WM, et al. A combination chemotherapy protocol (VELCAP-L) for dogs with lymphoma. J Vet Intern Med 1998;12:465470.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 7.

    Carter RF, Harris CK, Withrow SJ, et al. Chemotherapy of canine lymphoma with histopathological correlation: doxorubicin alone compared to COP as first treatment regimen. J Am Anim Hosp Assoc 1983;23:587596.

    • Search Google Scholar
    • Export Citation
  • 8.

    Postorino NC, Susaneck SJ, Withrow SJ, et al. Single agent therapy with Adriamycin for canine lymphosarcoma. J Am Anim Hosp Assoc 1989;25:221225.

    • Search Google Scholar
    • Export Citation
  • 9.

    Mutsaers AJ, Glickman NW, DeNicola DB, et al. Evaluation of treatment with doxorubicin and piroxicam or doxorubicin alone for multicentric lymphoma in dogs. J Am Vet Med Assoc 2002;220:18131817.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 10.

    Hahn KA, Richardson RC, Teclaw RF, et al. Is maintenance chemotherapy appropriate for the management of canine lymphoma? J Vet Intern Med 1992;6:310.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 11.

    Piek CJ, Rutteman GR, Teske E. Evaluation of the results of L-asparaginase-based continuous chemotherapy protocol versus a short doxorubicin-based induction chemotherapy protocol in dogs with lymphoma. Vet Q 1999;21:4449.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 12.

    Chun R, Garrett LD, Vail DM. Evaluation of a high-dose chemotherapy protocol with no maintenance therapy for dogs with lymphoma. J Vet Intern Med 2000;14:120124.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 13.

    Moore AS, Cotter SM, Rand WM, et al. Evaluation of a discontinuous treatment protocol (VELCAP-S) for canine lymphoma. J Vet Intern Med 2001;15:348354.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 14.

    Garrett LD, Thamm DH, Chun R, et al. Evaluation of a 6-month chemotherapy protocol with no maintenance therapy for dogs with lymphoma. J Vet Intern Med 2002;16:704709.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 15.

    Simon D, Nolte I, Eberle N, et al. Treatment of dogs with lymphoma using a 12-week, maintenance-free combination chemotherapy protocol. J Vet Intern Med 2006;20:948954.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 16.

    Armitage JO, Mauch PM, Harris NL, et al. Non-Hodgkin's lymphoma. In: DeVita DT, Hellman S, Rosenberg SA, eds. Cancer: principles and practice of oncology. Philadelphia: Lippincott Williams & Wilkins, 2001;22562303.

    • Search Google Scholar
    • Export Citation
  • 17.

    Owen LN. TNM classification of tumors in domestic animals. Geneva: World Health Organization, 1980;4647.

  • 18.

    Culmsee K, Simon D, Mischke R, et al. Possibilities of flow cytometric analysis for immunophenotypic characterization of canine lymphoma. J Vet Med A Physiol Pathol Clin Med 2001;48:199206.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 19.

    Veterinary Co-Operative Oncology Group. Veterinary Co-Operative Oncology Group—common terminology criteria for adverse events (VCOG-CTCAE) following chemotherapy or biological antineoplastic therapy in dogs and cats v1.0. Vet Comp Oncol 2004;2:194213.

    • Search Google Scholar
    • Export Citation
  • 20.

    Teske E, van Heerde P, Rutteman GR, et al. Prognostic factors for treatment of malignant lymphoma in dogs. J Am Vet Med Assoc 1994;205:17221728.

    • Search Google Scholar
    • Export Citation
  • 21.

    Ruslander DA, Gebhard DH, Tompkins MB, et al. Immunophenotypic characterization of canine lymphoproliferative disorders. In Vivo 1997;11:169172.

    • Search Google Scholar
    • Export Citation
  • 22.

    Valerius KD, Ogilvie GK, Mallinckrodt CH, et al. Doxorubicin alone or in combination with asparaginase, followed by cyclophosphamide, vincristine, and prednisone for treatment of multicentric lymphoma in dogs: 121 cases (1987–1995). J Am Vet Med Assoc 1997;210:512516.

    • Search Google Scholar
    • Export Citation
  • 23.

    Myers NC III, Moore AS, Rand WM, et al. Evaluation of a multidrug chemotherapy protocol (ACOPA II) in dogs with lymphoma. J Vet Intern Med 1997;11:333339.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 24.

    Dobson JM, Blackwood LB, McInnes EF, et al. Prognostic variables in canine multi-centric lymphosarcoma. J Small Anim Pract 2001;42:377384.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 25.

    Boyce KL, Kitchell BE. Treatment of canine lymphoma with COPLA /LVP. J Am Anim Hosp Assoc 2000;36:395403.

  • 26.

    MacEwen EG, Brown NO, Patnaik AK, et al. Cyclic combination chemotherapy of canine lymphosarcoma. J Am Vet Med Assoc 1981;178:11781181.

    • Search Google Scholar
    • Export Citation
  • 27.

    Cotter SM, Goldstein MA. Treatment of lymphoma and leukaemia with cyclophosphamide, vincristine, and prednisone. I: treatment of dogs. J Am Anim Hosp Assoc 1987;19:159165.

    • Search Google Scholar
    • Export Citation
  • 28.

    Glasgow RE, Magid DJ, Beck A, et al. Practical clinical trials for translating research to practice: design and measurement recommendations. Med Care 2005;43:551557.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 29.

    Yessaian A, Mendivil AA, Brewster WR. Population characteristics in cervical cancer trials: search for external validity. Am J Obstet Gynecol 2005;192:407413.

    • Crossref
    • Search Google Scholar
    • Export Citation

Appendix

Multiagent chemotherapeutic protocol used in a study comparing response rates and remission and survival times in dogs with lymphoma treated with a continuous, multiagent, doxorubicin-based chemotherapeutic protocol or with a short-term single-agent protocol incorporating doxorubicin.

Induction phase
Week 1: L-asparaginase (400 U/kg [182 U/lb], SC), vincristine (0.7 mg/m2, IV), and prednisolone (30 mg/m2, PO, q 24 h for 7 days)
Week 2: Cyclophosphamide (200 mg/m2, IV) and prednisolone (20 mg/m2, PO, q 24 h for 7 days)
Week 3: Doxorubicin* (30 mg/m2, IV over 30 minutes) and prednisolone (10 mg/m2, PO, q 24 h for 7 days)
Week 4: Vincristine
Week 5: Cyclophosphamide
Week 6: Doxorubicin
Maintenance phase
Week 8: Vincristine
Week 10: Cyclophosphamide
Week 12: Vincristine
Week 14: Doxorubicin
Weeks 16 through 52: Repeat cycle for weeks 8 through 14, alternating doxorubicin and methotrexate (0.7 mg/kg, IV) until cumulative doxorubicin dose is 180 mg/m2, then replace doxorubicin with methotrexate
Weeks 55 through 104: Repeat cycle for weeks 8 through 14, except with a 3-week interval between treatments.
Weeks 108 through 130: Repeat cycle for weeks 8 through 14, except with a 4-week interval between treatments, then discontinue chemotherapy.

Administer dexamethasone (0.5 mg/kg, IV) prior to administration of each dose of doxorubicin.

  • Figure 1—

    Kaplan-Meier curves of remission times for dogs with lymphoma that had a complete remission following treatment with a continuous, multiagent chemotherapeutic protocol (n = 63; solid line) or a single-agent protocol involving doxorubicin (14; dotted line). Groups were not significantly (P = 0.63) different.

  • Figure 2—

    Kaplan-Meier curves of survival times for dogs with lymphoma that had a complete remission following treatment with a continuous, multiagent chemotherapeutic protocol (n = 63; solid line) or a single-agent protocol involving doxorubicin (14; dotted line). Groups were not significantly (P = 0.88) different.

  • 1.

    Dorn CR, Taylor DO, Schneider R, et al. Survey of animal neoplasms in Alameda and Contra Costa Counties, California. II. Cancer morbidity in dogs and cats from Alameda County. J Natl Cancer Inst 1968;40:307318.

    • Search Google Scholar
    • Export Citation
  • 2.

    Dorn CR, Taylor DO, Schneider R. The epidemiology of canine leukaemia and lymphoma. Bibl Haematol 1970;36:403415.

  • 3.

    Dobson JM, Samuel S, Milstein H, et al. Canine neoplasia in the UK: estimates of incidence rates from a population of insured dogs. J Small Anim Pract 2002;43:240246.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4.

    Greenlee PG, Filippa DA, Quimby FW, et al. Lymphomas in dogs. A morphologic, immunologic, and clinical study. Cancer 1990;66:480490.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5.

    Keller ET, MacEwen EG, Rosenthal RC, et al. Evaluation of prognostic factors and sequential combination chemotherapy with doxorubicin for canine lymphoma. J Vet Intern Med 1993;7:289295.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6.

    Zemann BI, Moore AS, Rand WM, et al. A combination chemotherapy protocol (VELCAP-L) for dogs with lymphoma. J Vet Intern Med 1998;12:465470.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 7.

    Carter RF, Harris CK, Withrow SJ, et al. Chemotherapy of canine lymphoma with histopathological correlation: doxorubicin alone compared to COP as first treatment regimen. J Am Anim Hosp Assoc 1983;23:587596.

    • Search Google Scholar
    • Export Citation
  • 8.

    Postorino NC, Susaneck SJ, Withrow SJ, et al. Single agent therapy with Adriamycin for canine lymphosarcoma. J Am Anim Hosp Assoc 1989;25:221225.

    • Search Google Scholar
    • Export Citation
  • 9.

    Mutsaers AJ, Glickman NW, DeNicola DB, et al. Evaluation of treatment with doxorubicin and piroxicam or doxorubicin alone for multicentric lymphoma in dogs. J Am Vet Med Assoc 2002;220:18131817.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 10.

    Hahn KA, Richardson RC, Teclaw RF, et al. Is maintenance chemotherapy appropriate for the management of canine lymphoma? J Vet Intern Med 1992;6:310.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 11.

    Piek CJ, Rutteman GR, Teske E. Evaluation of the results of L-asparaginase-based continuous chemotherapy protocol versus a short doxorubicin-based induction chemotherapy protocol in dogs with lymphoma. Vet Q 1999;21:4449.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 12.

    Chun R, Garrett LD, Vail DM. Evaluation of a high-dose chemotherapy protocol with no maintenance therapy for dogs with lymphoma. J Vet Intern Med 2000;14:120124.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 13.

    Moore AS, Cotter SM, Rand WM, et al. Evaluation of a discontinuous treatment protocol (VELCAP-S) for canine lymphoma. J Vet Intern Med 2001;15:348354.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 14.

    Garrett LD, Thamm DH, Chun R, et al. Evaluation of a 6-month chemotherapy protocol with no maintenance therapy for dogs with lymphoma. J Vet Intern Med 2002;16:704709.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 15.

    Simon D, Nolte I, Eberle N, et al. Treatment of dogs with lymphoma using a 12-week, maintenance-free combination chemotherapy protocol. J Vet Intern Med 2006;20:948954.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 16.

    Armitage JO, Mauch PM, Harris NL, et al. Non-Hodgkin's lymphoma. In: DeVita DT, Hellman S, Rosenberg SA, eds. Cancer: principles and practice of oncology. Philadelphia: Lippincott Williams & Wilkins, 2001;22562303.

    • Search Google Scholar
    • Export Citation
  • 17.

    Owen LN. TNM classification of tumors in domestic animals. Geneva: World Health Organization, 1980;4647.

  • 18.

    Culmsee K, Simon D, Mischke R, et al. Possibilities of flow cytometric analysis for immunophenotypic characterization of canine lymphoma. J Vet Med A Physiol Pathol Clin Med 2001;48:199206.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 19.

    Veterinary Co-Operative Oncology Group. Veterinary Co-Operative Oncology Group—common terminology criteria for adverse events (VCOG-CTCAE) following chemotherapy or biological antineoplastic therapy in dogs and cats v1.0. Vet Comp Oncol 2004;2:194213.

    • Search Google Scholar
    • Export Citation
  • 20.

    Teske E, van Heerde P, Rutteman GR, et al. Prognostic factors for treatment of malignant lymphoma in dogs. J Am Vet Med Assoc 1994;205:17221728.

    • Search Google Scholar
    • Export Citation
  • 21.

    Ruslander DA, Gebhard DH, Tompkins MB, et al. Immunophenotypic characterization of canine lymphoproliferative disorders. In Vivo 1997;11:169172.

    • Search Google Scholar
    • Export Citation
  • 22.

    Valerius KD, Ogilvie GK, Mallinckrodt CH, et al. Doxorubicin alone or in combination with asparaginase, followed by cyclophosphamide, vincristine, and prednisone for treatment of multicentric lymphoma in dogs: 121 cases (1987–1995). J Am Vet Med Assoc 1997;210:512516.

    • Search Google Scholar
    • Export Citation
  • 23.

    Myers NC III, Moore AS, Rand WM, et al. Evaluation of a multidrug chemotherapy protocol (ACOPA II) in dogs with lymphoma. J Vet Intern Med 1997;11:333339.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 24.

    Dobson JM, Blackwood LB, McInnes EF, et al. Prognostic variables in canine multi-centric lymphosarcoma. J Small Anim Pract 2001;42:377384.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 25.

    Boyce KL, Kitchell BE. Treatment of canine lymphoma with COPLA /LVP. J Am Anim Hosp Assoc 2000;36:395403.

  • 26.

    MacEwen EG, Brown NO, Patnaik AK, et al. Cyclic combination chemotherapy of canine lymphosarcoma. J Am Vet Med Assoc 1981;178:11781181.

    • Search Google Scholar
    • Export Citation
  • 27.

    Cotter SM, Goldstein MA. Treatment of lymphoma and leukaemia with cyclophosphamide, vincristine, and prednisone. I: treatment of dogs. J Am Anim Hosp Assoc 1987;19:159165.

    • Search Google Scholar
    • Export Citation
  • 28.

    Glasgow RE, Magid DJ, Beck A, et al. Practical clinical trials for translating research to practice: design and measurement recommendations. Med Care 2005;43:551557.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 29.

    Yessaian A, Mendivil AA, Brewster WR. Population characteristics in cervical cancer trials: search for external validity. Am J Obstet Gynecol 2005;192:407413.

    • Crossref
    • Search Google Scholar
    • Export Citation

Advertisement