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Stereotactic body radiation therapy for treatment of injection-site sarcomas in cats: 11 cases (2008–2012)

Michael W. Nolan DVM, PhD, DACVR1, Lynn R. Griffin DVM2, James T. Custis DVM, MS, DACVR3, and Susan M. LaRue DVM, PhD, DACVS, DACVR4
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  • 1 Department of Environmental and Radiologic Health Sciences, Flint Animal Cancer Center, College of Veterinary Medicine and Biomedical Sciences, University of Colorado, Fort Collins, CO 80523.
  • | 2 Department of Environmental and Radiologic Health Sciences, Flint Animal Cancer Center, College of Veterinary Medicine and Biomedical Sciences, University of Colorado, Fort Collins, CO 80523.
  • | 3 Department of Environmental and Radiologic Health Sciences, Flint Animal Cancer Center, College of Veterinary Medicine and Biomedical Sciences, University of Colorado, Fort Collins, CO 80523.
  • | 4 Department of Environmental and Radiologic Health Sciences, Flint Animal Cancer Center, College of Veterinary Medicine and Biomedical Sciences, University of Colorado, Fort Collins, CO 80523.

Abstract

Objective—To evaluate outcomes of stereotactic body radiation therapy (SBRT) in cats with injection-site sarcomas (ISS) via assessment of local responses and recurrences, survival times, and complications.

Design—Retrospective case series.

Animals—11 cats with ISS.

Procedures—Medical records of cats that were treated with SBRT for ISS between June 2008 and July 2012 were reviewed; information on patient demographics (age, sex, and breed), oncological histories (including prior treatment and histologic grade), details of SBRT plans (tumor volume, treatment field sizes, and prescription), response to treatment (including toxicoses), progression-free intervals, and survival times were extracted.

Results—Acute radiation-associated toxicoses were infrequent and limited to mild, self-limiting dermatitis and colitis in 2 and 1 of the 11 cats, respectively. No late radiation-associated toxicoses were observed. The objective response rate was 8 of 11 cats; these patients either had a partial or complete response as determined on the basis of CT or physical examination findings. The median progression-free interval was 242 days, and the median overall survival time was 301 days; median follow-up time of censored subjects was 173 days.

Conclusions and Clinical Relevance—SBRT was completed in 3 to 5 days and was well tolerated when used to treat cats with ISS. Measurable tumor responses were achieved in most cats in this study. Stereotactic body radiation therapy provided a means for palliation of ISS; further investigation is required to determine whether SBRT is a valid treatment option for downstaging disease prior to definitive surgery.

Abstract

Objective—To evaluate outcomes of stereotactic body radiation therapy (SBRT) in cats with injection-site sarcomas (ISS) via assessment of local responses and recurrences, survival times, and complications.

Design—Retrospective case series.

Animals—11 cats with ISS.

Procedures—Medical records of cats that were treated with SBRT for ISS between June 2008 and July 2012 were reviewed; information on patient demographics (age, sex, and breed), oncological histories (including prior treatment and histologic grade), details of SBRT plans (tumor volume, treatment field sizes, and prescription), response to treatment (including toxicoses), progression-free intervals, and survival times were extracted.

Results—Acute radiation-associated toxicoses were infrequent and limited to mild, self-limiting dermatitis and colitis in 2 and 1 of the 11 cats, respectively. No late radiation-associated toxicoses were observed. The objective response rate was 8 of 11 cats; these patients either had a partial or complete response as determined on the basis of CT or physical examination findings. The median progression-free interval was 242 days, and the median overall survival time was 301 days; median follow-up time of censored subjects was 173 days.

Conclusions and Clinical Relevance—SBRT was completed in 3 to 5 days and was well tolerated when used to treat cats with ISS. Measurable tumor responses were achieved in most cats in this study. Stereotactic body radiation therapy provided a means for palliation of ISS; further investigation is required to determine whether SBRT is a valid treatment option for downstaging disease prior to definitive surgery.

Contributor Notes

Presented in abstract form at the Veterinary Cancer Society Annual Conference, Albuquerque, November 2011.

The authors thank Dr. Hiroto Yoshikawa, Frank Conway, Chana Fuller, and Billie Arceneaux for technical assistance and Drs. Joseph F. Harmon, Steve Jones, and Dongqing (David) Zhang for medical physics support.

Address correspondence to Dr. Nolan (Michael.Nolan@colostate.edu).