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Outcomes following surgical excision or surgical excision combined with adjunctive, hypofractionated radiotherapy in dogs with oral squamous cell carcinoma or fibrosarcoma

Julia Riggs MA, VetMB1, Vicki J. Adams DVM, PhD2, Joanna V. Hermer BVM&S3, Jane M. Dobson MA, DVetMed4, Suzanne Murphy BVM&S, MSc5, and Jane F. Ladlow MA, VetMB6
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  • 1 Queen's Veterinary School Hospital, Department of Veterinary Medicine, University of Cambridge, Cambridge, CB3 0ES England.
  • | 2 Vet Epi, Abbey Farm Cottage, Heath Rd, Ixworth, Suffolk, IP31 2JP England.
  • | 3 Queen's Veterinary School Hospital, Department of Veterinary Medicine, University of Cambridge, Cambridge, CB3 0ES England.
  • | 4 Queen's Veterinary School Hospital, Department of Veterinary Medicine, University of Cambridge, Cambridge, CB3 0ES England.
  • | 5 Animal Health Trust, Lanwades Park, Newmarket, CB8 7UU England.
  • | 6 Queen's Veterinary School Hospital, Department of Veterinary Medicine, University of Cambridge, Cambridge, CB3 0ES England.

Abstract

OBJECTIVE To compare outcomes of dogs treated surgically for oral, nontonsillar, squamous cell carcinomas (SCCs) and fibrosarcomas (FSAs) with outcomes of dogs treated with a combination of surgery and postoperative radiotherapy; to explore whether postoperative, hypofractionated radiotherapy improved outcomes of dogs with incomplete excisions; and to identify prognostic factors associated with outcome.

DESIGN Retrospective cohort study.

ANIMALS 87 client-owned dogs that had undergone maxillectomy or mandibulectomy for treatment of oral SCC or FSA between 2000 and 2009.

PROCEDURES Medical records were retrospectively reviewed. Survival analysis was performed with Kaplan-Meier and Cox regression analyses to evaluate potential prognostic factors associated with patient outcome.

RESULTS Median survival time (MST) for all 87 dogs was 2,049 days, but was not reached for dogs with SCC, and was only 557 days for dogs with FSA; tumor type was a significant predictor of survival time. Dogs undergoing postoperative radiotherapy after incomplete excision of oral SCCs had a significantly longer MST (2,051 days) than did dogs with incompletely excised tumors and no radiotherapy (MST, 181 days). Postoperative radiotherapy of dogs with incompletely excised FSAs did not appear to offer protective value (MST, 299 days with radiotherapy and 694 days without radiotherapy).

CONCLUSIONS AND CLINICAL RELEVANCE Wide-margin surgical excision should be considered the gold-standard treatment for dogs with oral SCC or FSA. For dogs with oral SCCs without clean surgical margins, survival times may be improved by providing postoperative, hypofractionated radiotherapy.

Abstract

OBJECTIVE To compare outcomes of dogs treated surgically for oral, nontonsillar, squamous cell carcinomas (SCCs) and fibrosarcomas (FSAs) with outcomes of dogs treated with a combination of surgery and postoperative radiotherapy; to explore whether postoperative, hypofractionated radiotherapy improved outcomes of dogs with incomplete excisions; and to identify prognostic factors associated with outcome.

DESIGN Retrospective cohort study.

ANIMALS 87 client-owned dogs that had undergone maxillectomy or mandibulectomy for treatment of oral SCC or FSA between 2000 and 2009.

PROCEDURES Medical records were retrospectively reviewed. Survival analysis was performed with Kaplan-Meier and Cox regression analyses to evaluate potential prognostic factors associated with patient outcome.

RESULTS Median survival time (MST) for all 87 dogs was 2,049 days, but was not reached for dogs with SCC, and was only 557 days for dogs with FSA; tumor type was a significant predictor of survival time. Dogs undergoing postoperative radiotherapy after incomplete excision of oral SCCs had a significantly longer MST (2,051 days) than did dogs with incompletely excised tumors and no radiotherapy (MST, 181 days). Postoperative radiotherapy of dogs with incompletely excised FSAs did not appear to offer protective value (MST, 299 days with radiotherapy and 694 days without radiotherapy).

CONCLUSIONS AND CLINICAL RELEVANCE Wide-margin surgical excision should be considered the gold-standard treatment for dogs with oral SCC or FSA. For dogs with oral SCCs without clean surgical margins, survival times may be improved by providing postoperative, hypofractionated radiotherapy.

Contributor Notes

Dr. Riggs' present address is Willows Veterinary Centre & Referral Service, Highlands Rd, Shirley, B90 4NH England. Dr. Hermer's present address is Taverham Veterinary Practice, Fir Covert Rd, Norwich, NR8 6HT England. Dr. Murphy's present address is The Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush Campus, Midlothian, EH25 9RG Scotland.

Address correspondence to Ms. Riggs (julia.riggs@cantab.net).