Which descriptor should spread through air spaces (STAS) be incorporated into? T descriptor versus residual tumor classification

It has not been determined which descriptor spread through air spaces (STAS) should be incorporated into the context of the ninth Tumor, Node and Metastasis (TNM) staging system: the T or the uncertain resection [R(un)] category. A multicenter retrospective cohort of 807 patients with pathological stage I lung adenocarcinoma was included in this study to assess the feasibility of incorporating STAS into the T descriptor or the R(un) category by analyzing recurrence-free survival (RFS) and overall survival (OS). Decision curve analysis (DCA) was performed to evaluate the standardized net benefit of the proposed T (nT) and that of the proposed residual tumor classification (nR) versus the current staging systems. Log-rank tests indicated that patients with pT1/STAS-positive lung adenocarcinoma had similar RFS and OS to patients with pT2a disease irrespective of R status. Regarding STAS as an indicator for upgrading R0 to R(un), comparable survival was observed between pT1-2a/STAS-positive patients undergoing R0 segmentectomy and pT1-2a patients undergoing R(un) segmentectomy. We further assessed the effects of the combination of STAS with either T or R category on survival in a validation cohort. Subgroup analyses stratified by surgical procedures further identified the consistency of the nT category in discriminating RFS and OS. However, the separation of nR0 and nR(un) disease in pT2a tumors treated by lobectomy or segmentectomy was not sufficiently distinguished. DCA further corroborated a greater predictive capability of nT versus the current T category. In conclusion, STAS might be preferentially considered as an indicator for upgrading pT1 disease into pT2a in the future TNM staging system.