Comparison of metastasis and treatment patterns among different histopathologic types of lung cancer: analysis of 6 years of nationwide lung cancer cohort data in Korea.

Background: Personalized management of stage IV lung cancer requires a deeper understanding of metastatic patterns and the potential benefits of localized treatments for each histologic type. This study aims to identify patterns of both intrathoracic and extrathoracic metastases across various histologic types of lung cancer using a nationwide Korean lung cancer database.

Methods: The study analyzed data from patients diagnosed with lung cancer between 2014 and 2019, sourced from the Korean Association of Lung Cancer Registry (KALC-R). Patients with stage IV lung cancer, indicated by M staging, were included to focus on metastatic patterns.

Results: The cohort included 7,562 stage IV lung cancer patients, with adenocarcinoma being the most prevalent histologic type, comprising 49.22% of cases (3,722 patients). M stage categorization showed that 27.3% were M1a, 56.3% M1b, 15.7% M1c, and 0.6% unspecified. The adenosquamous type had the highest proportion of patients with metastases in three or more organs (42.9%). Metastases to the liver and bones were consistently associated with decreased survival across histologic types. In adenocarcinoma, strong associations were observed between extrathoracic metastatic sites, particularly between bone and liver [odds ratio (OR) =3.93] and liver and adrenal glands (OR =2.85). Multivariate analysis revealed that patients receiving radiotherapy to lung lesions had significantly better overall survival (OS) [hazard ratio (HR) =0.68; 95% confidence interval (CI): 0.60-0.78; P<0.001] compared to those who did not. Radiotherapy to extrathoracic metastases also significantly improved survival (HR =0.84; 95% CI: 0.77-0.93; P<0.001).

Conclusions: Understanding metastasis patterns and treatment options specific to each lung cancer histologic type is essential for improving treatment strategies.