Reframing nodal staging in non–small-cell lung cancer: development and external validation of a metastatic node-count classification versus the 9th-edition N descriptor
Ji Yong Kim, Seunghee Baek, Geun Dong Lee, Sehoon Choi, Hyeong Ryul Kim, Yong-Hee Kim, Dong Kwan Kim, Seung-Il Park, Jae Kwang YunBackground:
The 9th-edition TNM system for non–small-cell lung cancer subdivides N2 disease. The number-based nodal (nN) classification has shown prognostic performance similar to that of the 8th N descriptor, but comparisons with the 9th N descriptor are limited. We aimed to identify statistically valid cutoffs for the nN classification and compare its prognostic discrimination with that of the 9th N descriptor.
Materials and methods:
Patients with non–small-cell lung cancer who underwent lobectomy or a more extensive resection were included in the study. The SEER database (2010–2022) served as the training cohort, and an institutional dataset (2005–2022) served as the validation cohort. These two cohorts were not merged and were analyzed independently. Optimal cutoffs for the nN classification were identified using pairwise log-rank tests and multivariable Cox models in the validation cohort. Prognostic performance for overall survival was assessed in the validation cohort.
Results:
A total of 18 294 patients in the training cohort and 7386 patients in the validation cohort were analyzed. In the training cohort, cutoffs of 1 and 4 metastatic lymph nodes were identified, defining four nN classes (0, 1, 2–4, and ≥5). In the validation cohort, 5-year overall survival rates by nN class were 85.6%, 68.7%, 61.2%, and 44.4%, and all adjacent class comparisons were significant in multivariable Cox models (
Conclusion:
In patients undergoing upfront surgery, the nN classification provides prognostic discrimination equivalent to the 9th N descriptor and may serve as a complementary tool. Its generalizability after neoadjuvant therapy remains uncertain.