Adjuvant carboplatin for treatment of splenic hemangiosarcoma in dogs: Retrospective evaluation of 18 cases (2011‐2016) and comparison with doxorubicin‐based chemotherapy

BACKGROUND: Doxorubicin‐based chemotherapy after splenectomy remains the standard of care for hemangiosarcoma in dogs, but prognosis is generally poor. HYPOTHESIS/OBJECTIVES: To determine clinical outcome with carboplatin chemotherapy after splenectomy compared to doxorubicin‐based protocols. A secondary objective was to determine if peripheral monocyte count was associated with prognosis. ANIMALS: Medical data from 40 dogs with histopathologically confirmed stage I or II hemangiosarcoma treated with splenectomy and carboplatin (n = 18) or doxorubicin‐based protocols (n = 22) were evaluated. METHODS: Retrospective study. Statistical associations were assessed using the Kaplan‐Meier method for survival times and log rank analysis for differences in survival time. Demographic information and survival times were obtained via medical records. Blood monocyte counts before and after surgery were documented. RESULTS: Median survival times were 160 days (48 to >559) and 139 days (54‐975), for dogs in the carboplatin (n = 18) and doxorubicin (n = 22) groups respectively (P = .82, hazards ratio [HR] [95% CI] = 1.075 [0.56‐2.07]). The median survival time for dogs whose monocyte counts decreased between splenectomy and chemotherapy initiation was 265 days, compared to 66 days for dogs with increased monocytes (P = .002, HR [95% CI] = 4.17 [1.21‐14.39]). CONCLUSIONS AND CLINICAL IMPORTANCE: Carboplatin could be considered as an alternative in cases where doxorubicin might be contraindicated. Increasing postoperative peripheral monocyte counts might be associated with a poorer prognosis.