Clinicopathological features and survival outcomes of resected lung adenosquamous carcinoma: results from a nationwide Japanese registry data

Objectives The objective of this study was to clarify the clinicopathological features and prognostic factors of resected lung adenosquamous carcinoma (ASC) using a nationwide multi-institutional database. Methods We retrospectively reviewed the records of 15,542 patients who underwent complete R0 resection for ASC (n = 326), adenocarcinoma (AC, n = 11,820), or squamous cell carcinoma (SC, n = 3,396) from a Japanese lung cancer registry in 2010. To reduce the selection bias, an inverse probability of treatment weighting (IPTW) method using a propensity score was implemented. Results The ASC group showed worse recurrence-free and overall survival (RFS and OS) than both the AC and SC groups (5-year OS: 57.5% in ASC, 83.9% in AC [<0.001], and 62.3% in SC [p = 0.086]). In multivariate analyses, prognostic factors that affected OS for ASC included male, p-stage II-III, and postoperative complications within 30 days (grade ≥3 in the Clavien-Dindo classification). The sensitizing EGFR mutation was detected in 28 (21.5%) of 130 screened patients with ASC, but it did not affect either RFS, OS, or post-recurrence survival. Although more patients in the ASC group received adjuvant chemotherapy compared to the AC and SC groups, both multivariate and IPTW-adjusted analyses did not show positive impact of adjuvant chemotherapy on RFS and OS in ASC. Conclusions In this nationwide registry study, lung ASC was more aggressive than both AC and SC. No apparent survival impact of conventional adjuvant chemotherapy prompted us to investigate novel adjuvant strategies to optimize survival outcomes. MicroAbstract The objective of this study was to clarify the clinicopathological features and prognostic factors of resected lung adenosquamous carcinoma (ASC) using a multi-institutional database. The ASC showed worse survival than both adenocarcinoma and squamous cell carcinoma, showing the aggressive biological behavior. No apparent survival impact of conventional adjuvant chemotherapy prompted us to investigate novel adjuvant strategies.