Short- and long-term outcomes associated with anal sacculectomy in dogs with massive apocrine gland anal sac adenocarcinoma
Maureen A. Griffin, Philipp D. Mayhew, William T. N. Culp, Michelle A. Giuffrida, Stephanie Telek, Ameet Singh, Michelle L. Oblak, Emmett Swanton
Abstract
OBJECTIVE: To evaluate short- and long-term outcomes for dogs undergoing anal sacculectomy for massive (> 5 cm) apocrine gland anal sac adenocarcinoma (AGASACA). ANIMALS: 28 client-owned dogs with massive AGASACA. PROCEDURES: A retrospective multi-institutional study was performed. Pre-, intra-, and post-operative data was collected, and variables were statistically analyzed for associations with progression-free interval (PFI) and overall survival (OS). RESULTS: At the time of anal sacculectomy, 19 (68%) dogs underwent concurrent iliosacral lymph node extirpation, including 17 of 18 (94%) dogs with suspected nodal metastasis preoperatively. Five (18%) dogs experienced grade 2 intraoperative complications. Ten (36%) dogs experienced postoperative complications, including 1 grade 3 and 1 grade 4 complication. No dogs had permanent fecal incontinence, tenesmus, or anal stenosis. Nineteen dogs received adjuvant chemotherapy, radiation, or both. Local recurrence occurred in 37% of dogs. Dogs with lymph node metastasis at surgery were more likely than dogs without metastasis to develop new/progressive lymph node metastasis (10/17 [59%] vs 0/10 [0%]; P = .003) and distant metastasis (7/17 [41%] vs 0/10 [0%]; P = .026). Median PFI was 204 days (95% CI, 145 to 392). Median OS was 671 days (95% CI, 225 to upper limit not reached). Nodal metastasis at the time of surgery was associated with shorter PFI (P = .017) but not OS (P = .26). Adjuvant therapy was not associated with outcome. CLINICAL RELEVANCE: Dogs with massive AGASACA experienced prolonged survival following anal sacculectomy despite a high incidence of local recurrence and metastasis. Lymph node metastasis at the time of surgery was a negative prognostic indicator for PFI but not OS.