Introduction

Gastrointestinal disturbances frequently lead to owners withdrawing their dogs from chemotherapy. Carboplatin is associated with gastrointestinal upset in both humans and dogs. The majority of toxicity and efficacy studies of carboplatin treatment in dogs assess myelosuppression. Gastrointestinal toxicity manifesting as vomiting and diarrhoea is often recorded as a secondary outcome if at all. Nausea is rarely investigated in dogs.

Method

Vomiting and diarrhoea (defined as gastrointestinal toxicity) and appetite and salivation (indicative of nausea and defined as such for this study) were assessed in 21 dogs receiving between 1 and 4 cycles of carboplatin for a variety of non-gastrointestinal tumours. Results were recorded prospectively by means of an owner-completed questionnaire issued at the start of each chemotherapy cycle. Owners recorded events over the proceeding 21 days following sequential carboplatin doses. The occurrence, frequency and severity of the gastrointestinal side-effects were noted and categorised according to the VCOG-CTCAE grading system for acute (days 0-1), delayed (days 2-7) and late (8-20) stages following carboplatin chemotherapy.

Results

In total, 58 cycles of carboplatin were administered to 21 dogs. Either vomiting or diarrhoea was seen in 17/58 cycles in the acute stage, 15/58 cycles in the delayed stage and 19/58 cycles in the late stage. Six dogs had vomiting or diarrhoea in all three stages. All episodes were mild and self limiting and did not require veterinary intervention. Only 4/21 dogs did not have any vomiting or diarrhoea at any stage. Nausea, defined as either excessive salivation or decreased appetite or both, was present in 29/58 cycles in the acute stage, 30/58 cycles in the delayed stage and 22/58 cycles in the late stage. Some form of gastrointestinal signs (toxicosis or nausea or both) was reported by owners of 20/21 dogs. For the majority of the 20 dogs with gastrointestinal signs, the severity of the signs according to the VCOG-CTCAE grading system was mild.

Conclusion

Gastrointestinal signs were recorded in 95% of cases, a higher frequency than previously reported or anticipated but was mild in the majority of cases. These findings emphasise the requirement to preemptively manage anticipated gastrointestinal toxicity and nausea in dogs receiving carboplatin chemotherapy in order to maintain both patient wellbeing and owner compliance.