Radiotherapy is one of the important local treatments for patients with non-small cell lung cancer. However, radiotherapy is often the biggest obstacle to the curative effect and the main cause of treatment failure. Looking for radiosensitivity markers is of great significance to discover specific resistance mechanism, improve efficacy and prognosis, and provide ideas and basis for radiosensitization treatment of non-small cell lung cancer.

Objective:To investigate the correlation between the waiting time for radiotherapy after induction chemotherapy and the prognosis of locally intermediate and advanced nasopharyngeal carcinoma, as well as its optimal time.Methods:Retrospective analysis of 101 patients with locally intermediate and advanced nasopharyngeal carcinoma admitted to the Fifth Affiliated Hospital of Sun Yat-sen University from 2017 to 2020 was performed. All patients received at least 2 courses of induction chemotherapy followed by radical radiotherapy. The waiting time for radiotherapy was defined as the time from the end of induction chemotherapy to the start of the first radiotherapy. The relationship between waiting time for radiotherapy and other factors (age, gender and stage, etc.) with progression-free survival (PFS), local recurrence-free survival (LRFS) and distant metastasis-free survival (DMFS) was analyzed through Cox model. The median waiting time for radiotherapy with 3 weeks was used as the boundary, and all patients were divided into ≤3 weeks and>3 weeks groups. The PFS, LRFS and DMFS between two groups were compared using Kaplan-Meier survival analysis. P<0.05 was considered as statistical significance. Results:Cox-regression analysis showed that the waiting time was correlated with PFS, LRFS, and DMFS (all P<0.05). Kaplan-Meier survival analysis suggested that the PFS, LRFS and DMFS in the ≤3 weeks group were significantly better than those in the >3 weeks group (all P<0.05). Under the premises of the T 3 stage, N 2 stage and the increased EB virus DNA replication levels before treatment, the PFS, LRFS and DMFS in the ≤3 weeks group were significantly better than those in the >3 weeks group (all P<0.05). Conclusions:The waiting time for radiotherapy is one of the factors affecting clinical prognosis of locally intermediate and advanced nasopharyngeal carcinoma. The earlier the time, the better the prognosis. Radiotherapy should be delivered within 3 weeks.