Analysis Of The Role Of Adjuvant Radiotherapy In N2 Non-Small Cell Lung Cancer After Radical Operation Using Propensity Score Matching

BackgroundN2 non-small cell lung cancer(NSCLC)is a heterogeneous disease.For operable patients with postoperative N2 non-small cell lung cancer,the optimum adjuvant treatment strategy is still in dispute.Our aim was to assess the efficacy of conbine postoperative chemoradiotherapy(POCRT)or postoperative chemotherapy(PCT)alone following surgery in pathological N2 non-small cell lung cancer using propensity score matching,and to explore the factors influencing the prognosis.MethodsBetween 2004 and 2014,a total of 175 patients fulfilled the inclusion criteria,of whom 115 patients were administered PCT and 60 patients received POCRT before matching,and 53 and 60 patients in each group after matching,respectively.The initiation of PCT started later than 2 weeks after the operation.The regimens of PCT in the present study included a cisplatin-based regimen with docetaxel or gemcitabine or vinorelbine or pemetrexed(only for non-squamous NSCLC)and were administered for at least 2 cycles.Carboplatin was alternatively used in case of intolerance to cisplatin.POCRT was executed sequentially or sandwiched with PCT with three-dimensional conformal radiotherapy(3D-CRT)or intensity-modulated radiotherapy technique(IMRT).The prescription dose to clinical target volume(CTV)was 50(range 44-60)Gy,And the chemotherapy regimen and dose were the same as chemotherapy alone.The primary end points were overall survival(OS).Data were analyzed using SPSS version 24.0(IBM Corp.,Armonk,NY,USA).Survival curves were produced using the Kaplan-Meierestimator method and compared with the log-rank test.Univariable and multivariable analyses of clinical characteristics.All statistical tests were two-sided,with a threshold of p<0.05 for statistical significance.All available patient and tumor variables were compared using the ?2 test.Propensity score matching(PSM)analyses were used to compensate for differences in baseline characteristics between the POCRT and PCT groups to confirm the survival difference.The survival of the two groups was followed up and the effect of postoperative radiotherapy was analyzed.An exploratory subgroup analysis was performed to screen for the benefit of postoperative radiotherapy.Results1)Univariate analyses indicated that operation modality,T stage,total number of metastatic lymph nodes(MLNs),total chemotherapy cycles and POCRT were important prognostic factors affecting OS.2)Multivariate analyses indicated that T stage,total number of metastatic lymph nodes(MLNs)and POCRT were independent factors affecting OS.3)115 patients were administered PCT and 60 patients received POCRT before matching.No significant differences in clinical characteristics were identified between the two groups,with the exception of surgical modality and total number of chemotherapy cycles.The median survival time was 57 vs 40 months in the POCRT and PCT groups,and the 1,3 and 5-year OS rates in the POCRT and PCT groups were 98.3 vs.86.1%,71.7 vs.53.0% and45.7 vs.39.0%,respectively(P=0.019).Exploratory subgroup analysis found that compared with PCT,POCRT improved OS in patients with squamous cell subtype(P=0.010),no lymphovascular invasion(P=0.006),pN2a(P=0.006)or total number of metastatic lymph nodes ?7(P=0.016).4)Following PSM,a total of 113 events were identified in both the POCRT and PCT groups,with 60 and 53 patients in each group,respectively.There was no significant difference in the general clinical data between the two groups after matching.The median survival time was 57 vs63 months in the POCRT and PCT groups after matching,and the 1,3 and 5-year OS rates in the POCRT and PCT groups were 98.3 vs.92.5%,71.7 vs.64.2% ?45.7 vs.50.7% respectively,with no significant difference(P=0.463).Following PSM,the survival differences between POCRT and PCT in the various subgroups were not statistically significant,except in patients with squamous cell lung cancer(P=0.010).ConclusionsUnivariate and multivariate analyses indicated that T stage,total number of MLNs and POCRT were independent factors affecting OS.POCRT following complete resection clearly demonstrated superior survival compared with PCT.And POCRT may be beneficial for N2 patients with squamous cell lung cancer,particularly those with limited nodal involvement and T4 disease.