Lepidic-Type Lung Adenocarcinomas: Is It Safe to Observe for Growth Prior to Treating?

Background Lepidic-type adenocarcinomas (LPA) can be multi-focal, and treatment is often deferred until there is observed growth. This study investigated the potential downside of that strategy by evaluating the relationship of nodal involvement with tumor size and survival. Methods The impact of tumor size on lymph node involvement and survival was evaluated for National Cancer Database patients who received surgery without induction therapy as primary treatment for cT1-3N0M0 histologically confirmed LPA from 2006-2019 using logistic regression, Kaplan-Meier, and Cox analyses. Results Positive nodes occurred in 442 (5.3%) of 8,286 patients. The incidence of having positive nodes approximately doubled with each 1cm increment increase in size. Patients with positive nodes were more likely to have larger tumors (27mm vs 20mm,p<0.001) and clinical T2+ disease (40.7% vs 26.8%,p<0.001) compared to node-negative patients, but tumor size was the only significant independent predictor of having positive nodal disease in logistic regression analysis; this association grew stronger with each incremental centimeter increase in size. Patients with positive nodes were more likely to undergo adjuvant radiation (23.5% vs 1.1%,p<0.001) and chemotherapy (72.9% vs 7.9%,p<0.001), and expectedly had worse survival compared to the node negative group in univariate (5-year overall survival 50.9% vs 81.1%,p<0.001) and multivariable (Hazard ratio 2.56 [95% CI 2.14-3.05],p<0.001) analyses. Conclusions Nodal involvement is relatively uncommon in early-stage LPAs but steadily increases with tumor size and is associated with dramatically worse survival. This data can be used to inform treatment decisions when evaluating LPA patients.