Alternative endpoints to the 5-year overall survival and locoregional control for nasopharyngeal carcinoma: A retrospective analysis of 2,450 patients

The purpose of the present study was to investigate alternative endpoints to the 5-year overall survival (OS) and locoregional control (LRC) for nasopharyngeal carcinoma (NPC). A total of 2,450 NPC patients were enrolled in this study, including 1,842 patients treated with two-dimensional (2D) radiotherapy (RT), 451 treated with 3D conformal RT (CRT) and 157 treated with intensity-modulated RT (IMRT). We sequentially calculated the 1-, 2-, 3- and 4-year survival rates using a life table and compared these with the 5-year survival rate using the McNemar method, with the survival rate of the last indifferent comparison being considered as the alternative endpoint. For 2D RT, stage I patients exhibited similar survival rates at 1 and 5 years (98.9 vs. 94.4%, respectively; P=0.125 for both OS and LRC); stage N3 patients exhibited similar 4-year OS (55.2 vs. 53.5%; P=1.000) and 2-year LRC (78.3 vs. 71.2%; P=0.125) to the 5-year OS and LRC. For IMRT, the 1-, 2-, 3-, 4- and 5-year OS and LRC rates in stage I/II NPC patients were 100, 98, 96, 94 and 94% for OS and 100, 98, 96, 96 and 96% for LRC, respectively. No significant differences were observed for all the comparisons. For stage III/IV NPC patients treated with IMRT, the 1-, 2-, 3-, 4- and 5-year rates were 99.1, 96.3, 92.5, 88.8 and 85.0% for OS and 98.1, 97.2, 95.3, 90.7 and 89.7% for LRC, respectively. Only the 4-year OS and LRC rates were indifferent from those at 5 years (P=0.125 for OS and P=1.00 for LRC). In conclusion, the 1-year OS and LRC for stage I NPC patients treated with 2D RT or stage I/II NPC patients treated with IMRT, the 4-year OS and 2-year LRC for stage N3 NPC patients treated with 2D RT and the 4-year OS and LRC for stage III/IV NPC patients treated with IMRT were determined as the alternative endpoints to the 5-year OS and LRC for NPC patients.