Survival analysis of different treatment modalities and associated outcomes for canine primary pulmonary carcinoma

Primary pulmonary carcinoma (PPC) represents about 1% of all canine malignancies. This study retrospectively evaluated the clinical presentation and survival outcomes of 39 dogs with PPC in Hong Kong across different treatment modalities. Treatment groups were categorized as "surgery alone," "surgery and chemotherapy," "chemotherapy alone," and "no treatment." Chemotherapy protocols were further classified as maximum tolerated dose and metronomic chemotherapy. Advanced-stage diseases (stage III or above) were the most prevalent (n = 27, 64.1%). Survival times varied significantly across treatment groups (p < 0.001). Dogs treated with surgery alone had the longest median survival time (568 days), while those receiving adjuvant maximum tolerated dose chemotherapy post-surgery had a significantly shorter time to progression compared to surgery alone (143 vs. 427 days, p = 0.013). Among non-surgical cases, chemotherapy significantly prolonged median survival time compared to no treatment (p = 0.006). Tumor-related mortality was highest in untreated cases (77.8%). Chemotherapy achieved stable disease in 57.1% and partial response in 28.6% of advanced-stage patients, indicating potential benefits to delay life-threatening signs and improve quality of life. Metronomic chemotherapy protocols conferred a progression free interval 3 times longer than maximum tolerated dose chemotherapy (168 vs. 52 days; p = 0.028). This study is the first to report survival outcomes of untreated PPC cases, and second in veterinary literature to highlight the therapeutic potential of metronomic chemotherapy in managing advanced-stage canine PPC. Further prospective studies are warranted to evaluate the efficacy and toxicity profiles of individual therapies.