Prognostic value and predictive threshold of tumor volume for patients with locally advanced nasopharyngeal carcinoma receiving intensity-modulated radiotherapy

Background： Gross target volume of primary tumor（GTV-P） is very important for the prognosis prediction of patients with nasopharyngeal carcinoma（NPC）, but it is unknown whether the same is true for locally advanced NPC patients treated with intensity-modulated radiotherapy（IMRT）. This study aimed to clarify the prognostic value of tumor volume for patient with locally advanced NPC receiving IMRT and to ind a suitable cut-of value of GTV-P for prognosis prediction.Methods： Clinical data of 358 patients with locally advanced NPC who received IMRT were reviewed. Receiver oper-ating characteristic（ROC） curves were used to identify the cut-of values of GTV-P for the prediction of diferent end-points [overall survival（OS）, local relapse-free survival（LRFS）, distant metastasis-free survival（DMFS）, and disease-free survival（DFS）] and to test the prognostic value of GTV-P when compared with that of the American Joint Committee on Cancer T staging system.Results： The 358 patients with locally advanced NPC were divided into two groups by the cut-of value of GTV-P as determined using ROC curves： 219（61.2%） patients with GTV-P ≤46.4 mL and 139（38.8%） with GTV-P 〉46.4 mL. The 3-year OS, LRFS, DMFS, and DFS rates were all higher in patients with GTV-P ≤46.4 mL than in those with GTV-P 〉 46.4 mL（all P 〈 0.05）. Multivariate analysis indicated that GTV-P 〉46.4 mL was an independent unfavorable prognostic factor for patient survival. The ROC curve veriied that the predictive ability of GTV-P was superior to that of T category（P 〈 0.001）. The cut-of values of GTV-P for the prediction of OS, LRFS, DMFS, and DFS were 46.4, 57.9, 75.4 and 46.4 mL, respectively.Conclusion： In patients with locally advanced NPC, GTV-P 〉46.4 mL is an independent unfavorable prognostic indi-cator for survival after IMRT, with a prognostic value superior to that of T category.