Distant metastasis patterns among lung cancer subtypes and impact of primary tumor resection on survival in metastatic lung cancer using SEER database

This research aimed to systematically uncover the metastatic characteristics and survival rates of lung cancer subtypes and to evaluate the impact of surgery at the primary tumor site on cancer-specific survival in DM lung cancer. We used the Surveillance, Epidemiology, and End Results (SEER) database (2010-2019) to identify primary lung cancers with DM at presentation (M1). Kaplan-Meier (KM) survival curves were generated and compared utilizing log-rank tests. Cox regression methods were employed to determine hazard ratios (HR) and 95% confidence intervals related to CSS factors. Inverse probability of treatment weighting (IPTW) was applied to reduce bias. We analyzed 77,827 M1 lung cancer cases, with 41.22% having DM at presentation. Bone metastasis was most common in ADC, ASC, SCC, LCC; brain in LCNEC; liver in SCLC. Lung was common in TC + AC and SCC. Long-term survival was best in TC + AC and worst in SCLC (p < 0.001). Male gender, age < 50, primary tumor site (main bronchus, lower lobe), large tumor diameter, ADC/SCLC/SCC pathology, and regional lymph node involvement were significant risk factors for multiorgan metastasis. Age ≥ 50, male, large tumor diameter, positive lymph nodes, and multiorgan metastases were associated with lower CSS. In contrast, radiotherapy, chemotherapy, systemic therapy, and surgery were associated with higher CSS rates. Primary tumor resection improved survival in lung cancer patients (excluding small cell lung cancer, SCLC) with single organ metastases (KM log rank p < 0.001, HR = 0.6165; 95% CI (0.5468-0.6951)), especially in brain (p < 0.001, HR = 0.6467; 95% CI (0.5505-0.7596)) and bone (p = 0.182, HR = 0.6289; p < 0.01), but not in liver or intrapulmonary metastases after IPTW. Significant differences in DM patterns and corresponding survival rates exist among lung cancer subtypes. Primary tumor resection improves survival in lung cancer patients (excluding small cell lung cancer, SCLC) with single organ metastases, with better outcomes in patients with brain and bone metastases, while no significant benefit was seen in patients with liver and intrapulmonary metastases.