Accelerated fractionated radiotherapy with twice-daily treatment shows promise in treating dogs with locally advanced gingival squamous cell carcinoma

Abstract

Objective: To describe the treatment, response, and outcome for the use of accelerated fractionated radiotherapy with twice-daily treatment in dogs with locally advanced gingival squamous cell carcinoma (SCC).

Animals: 14 client-owned dogs with locally advanced gingival SCC but no evidence of metastasis treated with accelerated fractionated radiotherapy at the Animal Medical Center of Gifu University from November 2017 through August 2023.

Clinical presentation: The dogs had a median age of 12 years (range, 8 to 16 years) and a median body weight of 6.3 kg (range, 2.0 to 13.8 kg). Tumors were located in the maxilla (n = 12) or mandible (2) and were staged as T1 (1), T2 (9), or T3 (4) based on WHO criteria.

Results: All dogs underwent twice-daily accelerated fractionated radiotherapy using 3-D conformal planning, totaling 42 to 49 Gy in 10 to 14 fractions. Complete response was seen in 7 dogs, partial response in 6, and stable disease in 1, for an overall response rate of 93%. The most notable acute adverse effect was oronasal fistula (grade 4 toxicity per Veterinary Radiation Therapy Oncology Group criteria). Mild to moderate acute toxicities in oral cavity, skin, and eye (grade 1 to 3) were transient and manageable. Median progression-free survival was 222 days; median overall survival was 322 days.

Clinical relevance: The findings suggested that accelerated fractionated radiotherapy with twice-daily treatment may serve as a practical treatment option for dogs with locally advanced gingival SCC. Additional studies are warranted to confirm long-term efficacy and safety.

Keywords: cancer in dogs; fractionated radiotherapy; gingival SCC; oral squamous cell carcinoma; radiation toxicities.