Nomograms for intraoperative prediction of lymph node metastasis in clinical stage IA lung adenocarcinoma.

Background: Accurate prediction of lymph node metastasis (LNM) is critical for selecting optimal surgical procedures in early-stage lung adenocarcinoma (LUAD). This study aimed to develop nomograms for intraoperative prediction of LNM in clinical stage IA LUAD.

Methods: A total of 1227 patients with clinical stage IA LUADs on computed tomography (CT) were enrolled to construct and validate nomograms for predicting LNM (LNM nomogram) and mediastinal LNM (LNM-N2 nomogram). Recurrence-free survival (RFS) and overall survival (OS) were compared between limited mediastinal lymphadenectomy (LML) and systematic mediastinal lymphadenectomy (SML) in the high- and low-risk groups for LNM-N2, respectively.

Results: Three variables were incorporated into the LNM nomogram and the LNM-N2 nomogram, including preoperative serum carcinoembryonic antigen (CEA) level, CT appearance, and tumor size. The LNM nomogram showed good discriminatory performance, with C-indexes of 0.879 (95% CI, 0.847-0.911) and 0.880 (95% CI, 0.834-0.926) in the development and validation cohorts, respectively. The C-indexes of the LNM-N2 nomogram were 0.812 (95% CI, 0.766-0.858) and 0.822 (95% CI, 0.762-0.882) in the development and validation cohorts, respectively. LML and SML had similar survival outcomes among patients with low risk of LNM-N2 (5-year RFS, 88.1% vs. 89.5%, Pp = 0.790; 5-year OS, 96.0% vs. 93.0%, p = 0.370). However, for patients with high risk of LNM-N2, LML was associated with worse survival (5-year RFS, 64.0% vs. 77.4%, p = 0.036; 5-year OS, 66.0% vs. 85.9%, p = 0.038).

Conclusions: We developed and validated nomograms to predict LNM and LNM-N2 intraoperatively in patients with clinical stage IA LUAD on CT. These nomograms may help surgeons to select optimal surgical procedures.