Predictors of histologically confirmed local recurrence and no evident association of wound soaker catheter use with local recurrence in dogs with grade II-III mammary carcinomas: a retrospective cohort study.

Abstract

INTRODUCTION: Local recurrence after mammary surgery is a clinically relevant outcome in dogs with mammary carcinomas, yet recurrence-specific prognostic factors and the oncologic safety of wound soaker catheters (WSCs) remain insufficiently defined. METHODS: This retrospective cohort study aimed (1) to identify clinicopathologic factors associated with time to histologically confirmed local recurrence in dogs with grade II-III mammary carcinomas and (2) to evaluate whether WSCs delivering intermittent bupivacaine boluses were associated with the hazard of local recurrence. Standardized records from a veterinary teaching hospital were reviewed for female dogs undergoing nodulectomy, regional mastectomy, or unilateral radical mastectomy with histologic confirmation of grade II-III carcinoma. Local recurrence was strictly defined as histologic regrowth at or near the surgical site, and time to local recurrence was analyzed using Cox proportional hazards models. RESULTS: The cohort included 117 dogs (65.0% grade II; 35.0% grade III), of which 11 (9.4%) developed local recurrence, with a median time to recurrence of 6.4 months. In the multivariable model based on 107 complete cases, larger tumor size (hazard ratio [HR] 1.29 per 1-cm increase; 95% confidence interval [CI] 1.07-1.55) and histologic infiltration (HR 4.51; 95% CI 1.43-14.23) were independently associated with a higher hazard of local recurrence. WSC use was not associated with the hazard of local recurrence (HR 0.36; 95% CI 0.09-1.40), although the estimate was imprecise. DISCUSSION: Overall, these findings suggest that tumor size and histologic infiltration are associated with histologically confirmed local recurrence, and they do not provide evidence that WSC-based local analgesia increases the hazard of local recurrence within the limitations of this retrospective cohort.