Splenic stromal sarcomas in dogs: post splenectomy outcomes with and without adjuvant chemotherapy.

Abstract

INTRODUCTION: Stromal sarcomas are rare canine primary splenic tumors. Previous studies assessing outcomes in dogs with these tumors are limited by small sample sizes, with few dogs receiving adjuvant therapy, leaving the role of chemotherapy in these tumors unproven. METHODS: The aim of this multi-institutional, retrospective study was to compare outcomes for a larger number of dogs diagnosed with splenic stromal sarcomas, with a particular focus on the effectiveness of adjuvant therapy. Dogs with a histopathological diagnosis of splenic stromal sarcomas were enrolled. Outcomes were compared between dogs that received chemotherapy following splenectomy and those that did not. Furthermore, dogs were categorized based on the type of chemotherapy: a doxorubicin-based protocol versus a low-dose metronomic protocol, and outcomes were compared. Secondary aims were to reassess two previously identified prognostic factors: mitotic count (MC) and the presence of metastasis. RESULTS: A total of 115 dogs were included in the study. The median survival time using all dogs was 8.4 months. Of 115 dogs, 60 received adjuvant therapy post-splenectomy, of which 37 received a doxorubicin-based protocol. The use of adjuvant chemotherapy did not improve survival times in dogs with splenic stromal sarcoma. However, MC and the presence of metastasis at diagnosis were prognostic factors for death due to splenic sarcoma. For cases where the MC was ≥9 per 10 hpf, the hazard ratio was 2.27 (95% CI 1.16-4.45). For cases where there was evidence of metastasis at diagnosis, the hazard ratio was 2.19 (95% CI 1.05-4.58). Of 112 dogs staged at diagnosis, 16 had confirmed metastases. An additional 28 dogs developed metastases on repeat staging tests during the study. CONCLUSIONS: The use of adjuvant chemotherapy did not result in improved outcomes. MC and the presence of metastasis at diagnosis were prognostic factors for death due to splenic sarcoma.