Pulmonary carcinomas are infrequently documented in cats and intra/extrathoracic metastatic disease appears common. While surgery is the gold standard for operable tumours, there are no studies assessing the efficacy of medical treatment in cases of metastasis. The aim of this study was to determine the clinical response to chemotherapy in primary feline pulmonary carcinomas with evidence of metastatic disease.

Medical records from multiple institutions were searched for cats with cytologically or histopathologically confirmed primary pulmonary carcinomas, with concurrent computed tomography-suspected metastases, which subsequently underwent treatment with cytotoxic chemotherapeutics or tyrosine kinase inhibitor drugs. Cats that underwent surgical resection of the primary tumour and/or associated metastases were not included.

Thirteen cats were selected for inclusion. Median age was 12 years (range 6–16 years) and median body weight 3.9 kg (range 3.1–8.2 kg). Presenting clinical signs included coughing (9), tachypnoea (5), gastrointestinal signs (4), abdominal pain (1) and lethargy (1). A diffuse nodular pattern, consistent with metastasis to the lung parenchyma, was present in all cases; additional locations were identified in 6 cases (intrathoracic nodes [5], kidneys [1]). Medical treatments included vinorelbine (3), carboplatin (4), toceranib phosphate (4) and metronomic cyclophosphamide (2). All cats had variable improvement in clinical signs after initiation of treatment and experienced moderate to mild toxicity, with no cats requiring hospitalisation due to adverse events.

Overall median time to progression (TTP) with first-line medical treatment was 99 days (range 32–317 days). Four cats had evidence of disease progression while on chemotherapy and received rescue treatment, with a TTP ranging from 8 to 85 days. In 2 cases, only a clinical response could be assessed; of these, one had renal metastases at diagnosis and the other developed renal metastases while receiving treatment. These two patients initially demonstrated stable disease but later developed intraocular and retrobulbar metastases, respectively. Of patients with repeat imaging, 1 cat had a partial response, 6 had stable disease and 4 progressive disease. The overall median survival time was 139 days (range 50–497 days). Four cats were still alive at the time of data analysis with a median follow-up of 428 days (range 81–625 days).

This study suggests that chemotherapy may achieve stable disease in cats with primary, metastatic lung tumours. Extended survival times are possible, with some cats surviving over a year. Based on these results, medical treatment appears to be well tolerated and should be considered in advanced disease stage.

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