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

Background: Lepidic-type adenocarcinomas (LPAs) can be multifocal, and treatment is often deferred until growth is observed. 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 underwent surgery without induction therapy as primary treatment for cT1-3 N0 M0 histologically confirmed LPA from 2006 to 2019 by using logistic regression, Kaplan-Meier, and Cox analyses.

Results: Positive nodes occurred in 442 of 8286 patients (5.3%). The incidence of having positive nodes approximately doubled with each 1-cm increment increase in size. Patients with positive nodes were more likely to have larger tumors (27 mm vs 20 mm, P < .001) and clinical ≥T2 disease (40.7% vs 26.8%, P < .001) compared with node-negative patients. However, tumor size was the only significant independent predictor of having positive nodal disease in logistic regression analysis, and this association grew stronger with each incremental centimeter increase in size. Patients with positive nodes were more likely to undergo adjuvant radiotherapy (23.5% vs 1.1%, P < .001) and chemotherapy (72.9% vs 7.9%, P < .001), and expectedly, had worse survival compared with the node-negative group in univariate (5-year overall survival, 50.9% vs 81.1%, P < .001) and multivariable (hazard ratio, 2.56; 95% CI, 2.14-3.05; P < .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. These data can be used to inform treatment decisions when evaluating LPA patients.