Retrospective Safety Evaluation of Combined Chlorambucil and Toceranib for the Treatment of Different Solid Tumours in Dogs

Chlorambucil is used in veterinary medicine for various cancers, while Toceranib, which was licenced for treating canine mast cell tumours, is now used against other solid tumours. Both drugs are generally safe, but their combined use has not been studied. This study aimed to investigate retrospectively the safety profile of the Chlorambucil-Toceranib combination against canine solid tumours. Thirty-eight dogs received this combination. Chlorambucil was administered at a median dose intensity of 15.1 mg/m² per week, while Toceranib was given at the median dosage of 2.5 mg/kg on a Monday-Wednesday-Friday schedule. Dosages were individually adjusted according to commercially available tablet formulation, co-morbidities, and adverse events (AEs). The resulting clinical benefit rate (CBR) and overall response rate (ORR) were 55.3% and 10.5%, respectively. The median progressive free survival (PFS) and median survival time (MST) were 45.5 (12-537) days and 259 (42-1178) days, respectively. Gastrointestinal AEs occurred in 39.5% of cases (<i>n</i> = 15), 15.8% (<i>n</i> = 6) experienced UPC elevation, while hematological and biochemistry AEs affected 13.2% (<i>n</i> = 5) each. Most of these AEs were grades 1-2 (G1-2). None of the dogs interrupted treatment due to AEs, and the combination appeared safe. Larger prospective clinical trials are required to confirm our findings and investigate its efficacy across various cancers.