Analysis of prognostic factors and patterns of failure in dogs with malignant oral tumors treated with megavoltage irradiation

Alain P Theon, Carlos Rodriguez, Bruce R. Madewell

Research output: Contribution to journalArticlepeer-review

83 Scopus citations


Objective - To determine quality and duration of progression-free survival (PFS) time in dogs with malignant oral tumors after definitive megavoltage irradiation, to analyze prognostic factors for PFS time and patterns of failure, and to analyze the influence of tumor recurrence and development of metastasis on survival. Design - Prospective clinical trial. Animals - 105 dogs with squamous cell carcinoma, fibrosarcoma, or malignant melanoma of the oral cavity without evidence of metastasis. Procedure - Dogs were treated with 48 Gy over 4 weeks on an alternate-day schedule of 4 Gy/fraction. Multivariate analysis was done by use of Cox's regression model to determine significant prognostic factors and by use of a competing risk model to determine the differential effects of prognostic factors on type of, and time to, failure. In 8% of the dogs, severe acute radiation reactions in the final week of treatment resulted in treatment discontinuation. In 7.6% of the dogs, chronic radiation reactions, including bone necrosis and fistula formation, developed. Results - Prognostic factors that independently affected PFS time were histologic type and tumor T stage. Histologic type significantly influenced pattern of failure, but not time to failure, whereas clinical stage significantly influenced time to failure, but not type of failure. Clinical Implications - Irradiation was a safe and effective treatment of malignant oral tumors. Because the local efficacy of radiation was influenced only by tumor size, early treatment of oral tumors should improve the prognosis. In dogs without tumor recurrence, systemic metastases, rather than regional metastases, limited long-term survival after radiation therapy.

Original languageEnglish (US)
Pages (from-to)778-784
Number of pages7
JournalJournal of the American Veterinary Medical Association
Issue number6
StatePublished - Mar 15 1997

ASJC Scopus subject areas

  • veterinary(all)


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