Failure patterns and the influence of the TNM staging systems on prognosis in limited disease small cell lung Cancer (SCLC): the Turkish Oncology Group (TOG) study.

[PURPOSE] To determine recurrence patterns and prognostic factors in limited disease SCLC (LD-SCLC) and evaluate the effect of TNM classification on prognosis.

[MATERIAL AND METHODS] We retrospectively evaluated 266 patients with LD-SCLC who underwent curative chemoradiotherapy ± prophylactic cranial irradiation (PCI) between 2003 and 2016. These patients were recruited from 10 centers and restaged using the 7th and 8th TNM staging systems. We assessed the impact of TNM stage, age, gender, and PCI on all survival outcomes through univariate and multivariate analyses. Survival rates were calculated using the Kaplan-Meier method.

[RESULTS] The median follow-up period was 42 months. In all cases, the 2- and 5-year local recurrence-free survival (LRFS), distant metastasis-free survival (DMFS), and overall survival (OS) rates were 63.4-41.8%, 50.6-43.2%, and 50.9-27.7%, respectively. In the Cox regression analysis, N2-N3 disease and not receiving PCI were identified as poor prognostic factors for DMFS. In contrast, N2 disease, T4 stage according to the 8th TNM system, not receiving PCI, and thoracic RT doses < 60 Gy were recognized as prognostic factors negatively associated with OS. It was also observed that having N3 disease increases the risk of developing brain metastasis (BM) by a factor of 2.6.

[CONCLUSION] In our cohorts, the N category emerged as the most significant prognostic factor for overall survival, distant metastasis-free survival, and the development of brain metastasis. Considering that the definition of limited disease encompasses a broad spectrum of patients, TNM staging may be more beneficial in predicting patient prognosis and guiding treatment decisions, as suggested.