A population-based study of outcomes in surgically resected T3N0 non-small cell lung cancer in the Netherlands, defined using TNM-7 and TNM-8; justification of changes and an argument to incorporate histology in the staging algorithm?

PURPOSE: To study outcomes in patients surgically staged as pT3N0 non-small cell lung cancer (NSCLC) in a population registry, comparing TNM-7 and TNM-8 staging classifications.

MATERIALS AND METHODS: Details of patients who underwent surgery for a pT3N0M0 NSCLC from 2010 to 2013, based on the TNM-7 classification, were retrieved from the Netherlands Comprehensive Cancer Organization (IKNL). These were next matched with corresponding pathology data from a nationwide registry. Patients were categorized into 4 major pT3 subgroups: '> 7cm' tumor diameter, 'separate tumor nodules in the same lobe' (2nd+ nodule), 'parietal pleural invasion' and a 'mixed group' (mainly '> 7 cm' combined with 'parietal pleural invasion').

RESULTS: 683 patients were eligible for analysis. The 3- and 5-years overall survival (OS) for the subtype '> 7 cm' were 59.9% and 47.2%, respectively, and comparable to the subtype with pleural invasion were 50.4% and 45.3%, respectively. The 'mixed group' had a worse 3- and 5-year OS probability of 37.5% and 28.7%, which were comparable to outcomes for TNM-8 staged IIIB and pT4 cases in the IASLC database. For the subtype 2nd+ nodule, 3- and 5-year OS were 70.6% and 62.8%, respectively, with patients with adenocarcinoma showing a significantly better OS compared to squamous cell carcinoma: 5-years OS of 65.1% versus 47.2%, respectively (p<0.001), suggesting that prognosis for the adenocarcinoma subgroup may be comparable to the pT2 category, whereas squamous cell carcinoma nodules can remain pT3.

CONCLUSION: This population analysis of overall survivals in pT3N0 subcategories for NSCLC suggests that histology is a relevant descriptor in the 2nd+ nodule category. The findings do not support migration of the '>7 cm' group to the pT4 category in TNM-8, and suggest that a combination of two pT3 descriptors ('mixed group') merits migration to pT4.