Impact of Tumor Size and Differentiation Grade on Survival After Lobectomy and Segmentectomy for Patients with Early-Stage Lung Adenocarcinoma.

Background: The purpose of this study was to investigate the effect of tumor size and differentiation grade on long term survival in patients with early-stage lung adenocarcinoma (LUAD) after lobectomy and segmentectomy.

Patients and methods: Patients with stage T1-2N0M0 LUAD who underwent lobectomy and segmentectomy were identified from the Surveillance, Epidemiology, and End Results database. Patients were stratified as grade I (well differentiated), grade II (moderately differentiated), and grade III/IV (poorly differentiated/undifferentiated) carcinomas. The effect of tumor size on overall survival (OS) and lung cancer-specific survival (LCSS) was evaluated using the multivariate Cox regression model, including the interaction between tumor size, type of surgery, and tumor differentiation grade. The inverse probability of treatment weighting method was used to adjust for bias between the groups.

Results: A total of 19,857 patients were identified, including 18,759 (94.4%) who underwent lobectomy and 1098 (5.5%) who underwent segmentectomy. A three-way interaction among tumor size, differentiation grade, and type of surgery was observed in the overall cohort. After stratifying by differentiation grade, plots of interaction revealed that lobectomy was associated with improved survival compared with segmentectomy when the tumor size exceeded 23 mm for grade I LUAD and 14 mm for grade II LUAD. No interaction was observed between the studied factors in grade III/IV carcinomas.

Conclusions: This study interpreted the interaction between tumor size and type of surgery on long-term survival in patients with early stage LUAD and established a tumor size threshold beyond which lobectomy provided survival benefits compared with segmentectomy.