The influence of the metastasis pattern of mediastinal lymph nodes on the postoperative radiotherapy’s efficacy for the IIIA-pN2 non-small-cell lung cancer: a retrospective analysis of 220 patients

OBJECTIVE The use of postoperative radiotherapy (PORT) remains controversial for Stage IIIA-N2 non-small-cell lung cancer (NSCLC) patients, a possible reason is that IIIA-pN2 NSCLC diseases are a heterogeneous group with different clinicopathologic features. The aim of this research was to prove whether the mediastinal lymph nodes' (LNs) skipping status could indicate the necessity of the PORT for the pN2 NSCLC patients. METHODS The skip metastasis was defined as pN0N2 (no N1 LN involved), and nonskip metastasis was pN1N2 (one or more N1 LNs involved). Patients were divided into two groups: LNs nonskip and LNs skip, and postoperative chemoradiotherapy (POCRT) and postoperative chemotherapy. Then, the LN nonskip and LN skip groups were further divided into subgroups: POCRT and point of care testing (POCT) for subgroup analysis. RESULTS There were 220 cases included in the analysis, and 43 of them received PORT. On univariate analysis, the median 3-year progression-free survival (PFS) was, respectively, 16 months (27.7%) for the LN skip group and 11 months (15.3%) for the LN nonskip group (P=0.001). The median 3-year overall survival (OS) was, respectively, 35 months (47.0%) for the LN skip group and 27 months (38.7%) for the LN nonskip group (P=0.025). The median 3-year local recurrence-free survival (LRFS) was, respectively, 25 months (41.0%) for the LN skip group and19 months (29.9%) for the LN nonskip group (P=0.014). The median 3-year distant metastasis-free survival (DMFS) was, respectively, 22 months (32.5%) for the LN skip group and 15 months (20.4%) for the LN nonskip group (P=0.013). The median 3-year PFS was, respectively, 17 months (25.6%) for the POCRT group and 12 months (18.6%) for the POCT group (P=0.037). Although the POCRT group showed better OS, LRFS, and DMFS than the POCT group, the results showed no statistical significance. In subgroup analysis, there was no statistical significance in the Kaplan-Meier analysis between subgroups, but it showed that POCRT resulted in better PFS, OS, and DMFS in both LN skip and LN nonskip subgroups; this advantage was more obvious in the LN skip subgroup. CONCLUSION The LN skip status is closely related to the survival of the IIIA-N2 NSCLC disease, and the LN skip patients may get more benefit in PFS and LRFS than the LN nonskip patients from PORT.