A dose‐escalated radiation protocol of 10 × 4.0 Gy provides long‐term local control in canine apocrine gland anal sac adenocarcinoma

Objectives To obtain insights for establishing radiation therapy strategies that provide long‐term locoregional benefits in canine apocrine gland anal sac adenocarcinoma, we evaluated whether a dose‐escalated protocol (10 × 4.0 Gy) could improve clinical outcomes, particularly long‐term locoregional control, while maintaining acceptable toxicity. Materials and Methods This retrospective cohort study included dogs with apocrine gland anal sac adenocarcinoma treated with three‐dimensional conformal radiation therapy between September 2016 and September 2025. Dogs administered chemotherapy agents other than toceranib phosphate were excluded. Dogs were classified according to the radiation therapy protocol received as the dose‐escalated protocol group (10 × 4.0 Gy; Group A, n = 15) or the comparison group (8 × 3.8 Gy; Group B, n = 11). Outcomes included overall survival, progression‐free survival, local progression‐free survival and radiation‐related adverse effects. Results The median overall survival, progression‐free survival and local progression‐free survival of Group A (1534, 926 and 1554 days, respectively) were significantly longer than those of Group B (821, 258 and 351 days, respectively). The treatment response rate based on the 3‐month follow‐up CT examination was higher in Group A (90.9%) than in Group B (10.0%). The 1‐year local progression‐free survival rate was also higher in Group A (93.3%) than in Group B (45.5%). Additionally, all observed radiation‐related adverse effects were clinically manageable. Clinical Significance This retrospective cohort study demonstrated that the dose‐escalated 10 × 4.0 Gy protocol was associated with improved locoregional control and clinically manageable toxicity. Our findings suggest that dose escalation in apocrine gland anal sac adenocarcinoma therapy can be an effective strategy when sustained locoregional control is a clinical priority.