Retrospective evaluation of a modified human lung cancer stage classification in dogs with surgically excised primary pulmonary carcinomas.

The stage classification for canine primary pulmonary carcinomas (PPC) was last updated in 1980. In people, the human lung cancer stage classification (HLCSC) (currently in its eighth edition) plays an integral role in diagnostic and therapeutic decision-making and is prognostic despite a heterogeneous population of tumours. The objective of this retrospective case study was to evaluate the prognostic significance of a canine lung carcinoma stage classification (CLCSC) adapted from the HLCSC by removal of substage for ease of application to canine PPC. A secondary objective was to evaluate the effect of adjuvant chemotherapy. Medical records of 71 dogs with histologically confirmed PPC were reviewed. All dogs underwent surgical excision of the primary lung tumour. Primary tumour features (referring to T1-T4 stages) and TNM stages (1-4) were assigned using the CLCSC. Canine lung carcinoma stage was I (n = 7), II (n = 32), III (n = 24) and IV (n = 8). Median survival time was 952, 658, 158 and 52 days for stages I-IV, respectively. Primary tumour features (T1-T4), incomplete surgical excision, presence of lymph node metastasis and tumour grade were independent prognostic indicators for overall survival. Twenty-six dogs received adjuvant chemotherapy; however, no statistically significant benefit was found. The CLCSC primary tumour features and stage classification were highly prognostic for survival in dogs with PPC. We propose further application and evaluation of this update to canine PPC stage classification. Given the poor prognosis of advanced stage canine PPC, novel treatments are needed.