Prognostic impact of the 9th vs 8th TNM classification in small-cell lung cancer. a population-based study.

BACKGROUND

Small cell lung cancer (SCLC) is an aggressive malignancy with poor prognosis. The traditional limited and extensive-stage classification does not adequately capture disease heterogeneity. The tumor-node-metastasis (TNM) system has prognostic value in SCLC and is increasingly used, but the relevance of the 9th TNM edition in SCLC remains uncertain.

MATERIALS AND

METHODS

This retrospective, population-based study included patients with pathologically confirmed SCLC treated at Karolinska University Hospital, Sweden, between 2008 and 2022. Patients were reclassified according to the 8th and 9th TNM classifications. Survival was analyzed using Kaplan-Meier estimates and Cox proportional hazards regression.

RESULTS

The cohort encompassed 893 patients with a median age of 68 years; 58% were female. Stage migration between the 8th and 9th TNM classifications occurred in 49 (5.5%) patients and consisted exclusively of downstaging. Subdivision of mediastinal nodal disease showed a clear prognostic separation, with a median overall survival (mOS) of 11.7 months for N2a and 6.5 months for N2b (HR 1.8, 95% CI 1.4-2.2,p < 0.001); outcomes for N2b were comparable to N3 disease. Metastatic subclassification showed a modest but statistically significant prognostic difference, with mOS of 6.9 months for M1c1 and 4.8 months for M1c2 (HR 1.3, 95% CI 1.1-1.5,p = 0.008). Both N2 and M1c subclassifications showed independent associations with survival in multivariate analysis.

CONCLUSIONS

The 9th TNM classification provided additional prognostic stratification in SCLC. Refined nodal and metastatic subclassifications showed clear separation between groups. while stage migration was limited and had modest impact on stage-specific survival.