Photo Credit: Mohammed Haneefa Nizamudeen

Researchers recently validated the ninth edition of the TNM staging system for SCLC, finding improved accuracy and predictive power.

The tumor-node-metastasis (TNM) staging system plays a critical role in the prognostic assessment and treatment decisions for lung cancer. Guidelines recommend treatment modalities for patients with small-cell lung cancer (SCLC), which accounts for approximately 10% of the global incidence of lung cancer, based on the TNM classification.

The ninth edition of the TNM staging system (TNM-9) of lung cancer was presented at the 2023 World Conference on Lung Cancer, but there remained a need for proper external validation of the staging system. Previously, researchers validated the TNM-9 using data from the Surveillance, Epidemiology, and End Results (SEER) database from patients with non-small cell lung cancer who underwent lung resection. However, limited by flaws in the SEERS database, researchers could not further differentiate between N2a and N2b classifications.

To address this, and externally validate the TNM-9, researchers examined multicenter data from patients with limited-stage SCLC. The findings were reported in Lung Cancer.

The multicenter study included 408 patients diagnosed with limited-stage SCLC from 2004 to 2021 who underwent lung resection. The majority (86.8%) of patients were men. Most of the cohort (65.7%) were aged 65 or younger; 34.3% were older than 65 years. Surgical approaches included lobectomy (80.4%), sublobectomy (7.8%), and pneumonectomy (11.8%).

Improvements Across All Stages of SCLC

Researchers found that the TNM-9 staging system had improved distinguishing ability versus the eighth edition. These findings were observed across all stage groups that were compared (all P<0.05):

• IA versus IIB
• IIA versus IIB
• IIA versus IIIA
• IIA versus IIIB
• IIIA versus IIIB

Additionally, the TNM-9 demonstrated better predictive power and accuracy for the overall survival (OS) of patients with SCLC compared with the eighth edition:

• Area under the curve for 3-year OS: 0.680 versus 0.668
• Akaike information criterion: 4,425.25 versus 4,444.52
• Bayesian information criterion: 4,493.44 versus 4,512.71
• Concordance index, 0.637 [0.04] versus 0.629 [0.039]

“Our external validation demonstrates that the ninth edition of pathological TNM staging for limited-stage SCLC is reasonable and valid based on a multicenter study,” investigators wrote. “The ninth edition has better prognostic accuracy than the eighth edition.”