Retrospective comparison of first-line adjuvant anthracycline vs metronomic-based chemotherapy protocols in the treatment of stage I and II canine splenic haemangiosarcoma.

Splenectomy followed by adjuvant chemotherapy is commonly used to treat canine splenic haemangiosarcoma (HSA), although it is unclear if different treatment protocols may have a similar efficacy. The objective of this retrospective study was to assess outcome in dogs with stage I and II splenic HSA treated with either first-line adjuvant anthracycline (AC) or metronomic (MC)-based chemotherapy protocols, by comparing median time to progression (TTP) and median survival time (MST). Medical records of nine institutions were searched for dogs diagnosed with stage I and II splenic HSA that underwent adjuvant treatment with AC- or MC-based protocols following splenectomy. Patients treated with MC following AC were included in an additional group (AMC). Ninety-three dogs were included: 50 in the AC group, 23 in the AMC group and 20 in the MC group. The overall MST was 200 days (range 47-3352) and the overall median TTP was 185 days (range 37-1236). The median TTP of stage I dogs was significantly longer compared to stage II dogs (338 vs 151 days, respectively, P = .028). When adjusting for treatment type, the MST was 154 days for the AC group (range 47-3352 days), 338 days for the AMC group (range 79-1623 days) and 225 days for the MC group (range 57-911 days). The difference in MST and median TTP was not found to be statistically significant between treatment groups. This study suggests that adjuvant MC in canine splenic HSA may result in a similar outcome when compared to other treatment protocols. Further studies are warranted to confirm these findings.