Prognostic value of AJCC TNM Staging 7th edition in limited-stage small cell lung cancer: validation in 437 patients

Abstract

To explore the impact of AJCC TNM Staging 7th edition on survival outcome of limited stage small cell lung cancer (SCLC). Four hundred and thirty-seven SCLC patients with completed diagnosis and treatment data treated in our department between January 1996 and December 2006 were reclassified according to the AJCC TNM Staging 7th edition. The patients of stages IA, IB, IIA, IIB, IIIA, IIIB were 8, 44, 7, 64, 192 cases, respectively. Kaplan-Meier method was used for survival analysis and log-rank test was used to identify the prognostic factors. The survival rate was determined using chi-square test. The median follow-up time was 64 months. The median survival time was 26.2 months and median progression free survival time was 13.7 months. The 1-, 2- and 5-year overall survival rates were 86.0%, 52.7%, and 29.7%, respectively. The log-rank test showed that TNM stage is a statistically significant prognostic factor for OS in LS-SCLC (P<0.001). TNM staging system generally allowed a good separation in pairwise comparison for OS between successive stages except there was no significant difference between stages I and II (P=0.061). The 5-year progression free survival rates of patients of stage I, II, IIIA and IIIB were 53.2%, 43.2%, 16.8%, and 10.9%, respectively. TNM stage also was a statistically significant prognostic factor for PFS in LS-SCLC (P<0.001), but there was no significant difference between successive stages (P>0.05 for all). The T staging confirmed significant influence on OS (P<0.001) with no significant difference between successive stages (P>0.05 for all), while T stage was not a significant prognostic factor for PFS in the LS-SCLC patients (P=0.194). N stage also had a significant influence on OS (P<0.001), but with no significant differences between successive stages except N1 and N2 (P=0.001). N staging also showed significant influence on PFS (P=0.001), but with no significant difference between successive stages (P>0.05) except that between the 5-year survival rates of N2 and N3 cases (P=0.013). The cumulative brain metastasis rates of stages I, II, IIIA, and stage IIIB were 17.3%, 28.6%, 33.3%, and 35.8%, respectively(P=0.072), and were 12.8% and 30.8% for pathological stage I and clinical stage I (P=0.203). AJCC TNM Staging 7th edition criteria for LS-SCLC patients have a high prognostic impact and therefore are preferable in clinical practice and future therapeutic trials.