From TNM 8 to TNM 9: Stage Migration and Histology-Specific Patterns in Lung Cancer

Area of Science:

• Oncology
• Thoracic Surgery
• Cancer Staging

Background:

• The 9th edition of the TNM classification for lung cancer introduced revisions to N2 and M1c categories for enhanced precision.
• The impact of these TNM 9 revisions on stage distribution, histology-specific patterns, and clinical interpretation requires thorough evaluation.

Purpose of the Study:

• To compare lung cancer staging distributions between the 8th and 9th TNM editions.
• To analyze stage migration patterns and evaluate histology-specific reclassification trends under TNM 9.
• To assess the differential impact of TNM 9 staging on various lung cancer histological subtypes.

Main Methods:

• Retrospective analysis of lung cancer patients staged using both 8th and 9th TNM editions.
• Chi-squared tests for stage distribution alterations and McNemar's test for directional stage shifts (upstaging/downstaging).
• Correlation analysis between histological subtype and stage reclassification under TNM 9.

Main Results:

• Statistically significant redistribution of lung cancer stages observed with TNM 9 (χ² = 1013.03, p < 0.0001), showing a prevalence of upstaging (p = 0.0019).
• Stage IIIA showed the most significant proportional increase, largely due to the N2 subdivision (N2a vs. N2b).
• Adenocarcinoma demonstrated a higher tendency for reclassification into advanced stages (IIIA, IIIB) compared to squamous cell, small cell, and large cell carcinomas.

Conclusions:

• The 9th TNM edition causes significant stage migration, especially in adenocarcinoma, reflecting improved sensitivity to advanced nodal disease.
• TNM 9 modifications impact prognostic evaluation and global comparability, supporting its adoption as a more relevant staging system.
• Histology-specific patterns in stage migration align with international findings, confirming the prognostic value of N2 subdivision.