Recommended changes for T and N descriptors proposed by the International Association for the Study of Lung Cancer — Lung Cancer Staging Project: a validation study from a single-centre experience☆
Objective: The International Association for the Study of Lung Cancer (IASLC) recently recommended changes for T and N descriptors for the next TNM (Tumour, Node, Metastasis) edition. We re-classify our operated patients to evaluate the effectiveness of the IASLC suggestions. Methods: IASLC proposals include: (1) a subdivision of T1 into T1a (≤2 cm) and T1b (2–3 cm); (2) a subdivision of T2 into T2a (3–5 cm) and T2b (5–7 cm); (3) a re-assignment of T2 >7 cm to T3; (4) a re-assignment of intrapulmonary metastasis in the primary lobe (PM1) and in ipsilateral different lobes (PM2) from T4 to T3 and from M1 to T4, respectively; and (5) a classification of N descriptor by the number of involved lymph node zones into: N0; single-zone N1 (N1a); multiple-zone N1/single-zone N2 (N1b/N2a) and multiple-zone N2 (N2b). From 1994 to 2007, 1805 patients were operated on for non-small-cell lung carcinoma (NSCLC); survival analysis was performed using Cox proportional hazard model to assess the prognostic significance of the T and N descriptors. Results: Stratification by T descriptor was: T1a (362 patients), T1b (286), T2a (536), T2b (154), T2 >7 cm (58), T3 (243), PM1 (50) and PM2 (36). Stratification by N descriptor was: N0 (1150 patients), N1a (289), N1b/N2a (200) and N2b (67). A significant survival difference was found between T1a and T1b (hazard ratio (HR) 1.45, 95% confidence interval (CI): 1.10–1.90, p = 0.006) but not between T2a and T2b (HR: 1.11, 95% CI: 0.86–1.43, p = 0.38). Tumours >7 cm and PM1 had a survival similar to other T3 tumours (HR: 1.05, 95% CI: 0.97–1.14, p = 0.2 and HR: 0.99, 95% CI: 0.81–1.21, p = 0.94). An excellent patient stratification was provided with the proposed four-category nodal grouping, with significant survival differences between N0 and N1a (HR: 1.81, 95% CI: 1.50–2.21, p = 0.0000001), N1a and N1b/N2a (HR: 1.54, 95% CI: 1.21–2.00, p = 0.02) and between N1b/N2a and N2b (HR: 1.61, 95% CI: 1.14–2.27, p = 0.02). Conclusions: Our experience confirms the IASLC recommendations to subdivide patients by tumour size at 2, 3 and 7 cm, to re-assign PM1 tumours to T3 and to group patients according to the number of involved lymph nodal zones are valid and provide excellent survival stratification.