Validation of the 8th lung cancer TNM classification and clinical staging system in a German cohort of surgically resected patients

Abstract

Objectives: The updated 8th edition of the tumor, node, metastases (TNM) classification system for non-small cell lung cancer (NSCLC) attempts to improve on the previous 7th edition in predicting outcomes and guiding management decisions. This study sought to determine whether the 8th edition was more accurate in predicting long-term survival in a European population of surgically treated NSCLC patients.

Methods: We scanned the archives of the Heckeshorn Lung Clinic for patients with preoperative clinical stages of IIIA or lower (based on the 7th edition), who received surgery for NSCLC between 2009 and 2014. We used pathologists' reports and data on tumor size and location to reassign tumor stages according to the 8th edition. We then analyzed stage specific survival and compared the accuracy of the two systems in predicting long-term survival. We excluded patients with neoadjuvant treatment, incomplete follow-up data, tumor histologies other than NSCLC, or death within 30 days of surgery.

Results: The final analysis included 1,013 patients. Overall five-year survival was 47.3%. The median overall survival (OS) was 63 months (range 1-222), and the median disease-free survival (DFS) was 50 months (0-122). The median follow-up time for non-censored patients was 84 months (range 60-122).

Conclusions: We found significant survival differences between the newly defined stages 1A1, 1A2 and 1A3 (previously 1A). We also found that the 8th edition of TMN classification was a significantly better predictor of long-term survival, compared to the 7th edition.

Keywords: NSCLC; TNM; lung cancer; prognosis; staging; thoracic surgery; validation.

Figure 1:

Flow-chart demonstrating patient selection; NSCLC = non-small cell lung cancer.

Figure 2:

Kaplan-Meier curves with overall survival (OS) and disease free survival (DFS) by stage based on the 7th and 8th editions of TNM respectively. Log rank analysis of OS based on 7th TNM: IA vs. IB (p=0.6165), IB vs. IIA (p=0.812), IIA vs. IIB (p=0.085), IIB vs. IIIA (p<0.001), IIIA vs. IIIB (p=0.017); OS based on 8th TNM: IA1 vs 1A2 (p=0.039), IA2 vs. IA3 (p=0.998), IA3 vs. IB (p=0.681), IB vs. IIA (p=0.494), IIA vs. IIB (p=0.849), IIB vs. IIIA (p=<0.001), IIIA vs. IIIB (p<0.001); DFS based on 7th TNM: IA vs. IB (p=0.946), IB vs. IIA (p=0.630), IIA vs. IIB (p=0.019), IIB vs. IIIA (p=0.003), IIIA vs. IIIB (0.043); DFS based on 8th TNM: IA1 vs. 1A2 (p=0.084), IA2 vs. IA3 (p=0.775), IA3 vs. IB (p=0.484), IB vs. IIA (p=0.600), IIA vs. IIB (p=0.997), IIB vs. IIIA (p<0.001), IIIA vs. IIIB (p<0.001).