Proposal for Rib invasion as an independent T descriptor for non-small cell lung cancer: A propensity-score matching analysis

Abstract

IntroductionTo evaluate the prognosis between patients with non-small cell lung cancer (NSCLC) invading difference depth of chest wall and estimate the impact of rib invasion on the pathological T classifications (pT). MethodsWe retrospectively evaluated 521 patients with resected pT3-4 NSCLC. Propensity-score matching (PSM) balanced the known confounders of the prognosis, resulting in two sets (rib invasion vs the pT3 and pT4 group). Recurrence-free survival (RFS) and Overall survival (OS) was assessed by Cox regression and Kaplan-Meier methods. Time-dependent receiver operating characteristic (ROC) curves were used to assess the additional benefit for survival prediction after reclassifying rib invasion cases. ResultsChest wall invasion occurred in 171 patients (62 rib invasion, 51 parietal pleural invasion [PL3] and 58 soft tissue invasion). Rib invasion was found to be an independent prognostic factor for both RFS (p = 0.006) and OS (p < 0.001) of pT3-4 NSCLC. The survival of rib invasion group was the worst (RFS: 13.1%; OS: 19.8%), followed by PL3 (RFS: 34.2%, P = 0.001; OS: 48.8%; p < 0.001) and the soft tissue invasion group (RFS: 40.6%, p = 0.001; OS: 57.7%, p < 0.001). Besides, the prognosis of rib invasion group was also found to be worse than those of pT3 (RFS: p < 0.001; OS: p < 0.001) and pT4 group (RFS: p = 0.002; OS: p < 0.001). After PSM, the 5-year RFS rate of rib invasion group were still lower than that of pT3 and pT4 group (p < 0.001); the 5-year OS rate of rib invasion was similar with that of pT4 group (p = 0.066) but lower than that of pT3 group (p = 0.014). The time-dependent ROC curves demonstrated that reclassifying rib invasion as pT4 disease provided an additional benefit for survival prediction (p < 0.001). ConclusionThe rib invasion group had a worse prognosis than the PL3 and pT3 groups. The prognostic impact of rib invasion should be further validated as a pT4 disease in the TNM classification.