Evaluation of intracavitary carboplatin chemotherapy for treatment of pleural carcinomatosis in cats: a retrospective study of eight cases.

OBJECTIVES: The aim of this study was to evaluate the benefit of intracavitary carboplatin chemotherapy in cats with malignant pleural effusion of epithelial origin. METHODS: The medical records of cats with a cytological diagnosis of neoplastic pleural effusion of epithelial origin were reviewed at three referral institutions between January 2013 and June 2018. Only cats treated with intracavitary carboplatin chemotherapy were enrolled. Data collection included signalment, medical history, clinical signs, pleural effusion analysis, diagnostic imaging findings, intracavitary carboplatin chemotherapy protocol, adverse events, response to chemotherapy, outcome and underlying primary tumour, if possible. RESULTS: Eight cats met the inclusion criteria. Three cats had previous surgical removal of a tumour, including a poorly differentiated primary lung carcinoma, a uterine adenocarcinoma and a benign mammary tumour. The main clinical signs were tachypnoea and/or dyspnoea, inappetence and weight loss. Thoracic radiographs revealed marked bilateral pleural effusion in all cats. Pleural fluid analysis was consistent with a modified transudate, with malignant epithelial cells on cytology, leading to a diagnosis of pleural carcinomatosis. All cats received only one cycle of intracavitary carboplatin chemotherapy at a dose of 200-240 mg/m2. Recurrence of pleural effusion was reported in 7/8 cats within 4-15 days of chemotherapy, and death was recorded in all cats within 5-16 days, owing to recurrent pleural effusion or poor general condition. The primary cancer was suspected to be of pulmonary, mammary and pancreatic origin in four cats, two cats and one cat, respectively, and of unknown origin in the remaining cat. CONCLUSIONS AND RELEVANCE: In this study, intracavitary carboplatin chemotherapy seems ineffective in managing neoplastic pleural effusion of epithelial origin in cats with pleural carcinomatosis. Other cytotoxic drugs and/or techniques should be investigated in the future to improve the quality of life and survival of cats with pleural carcinomatosis.