Is primary tumor volume still a prognostic factor in intensity modulated radiation therapy for nasopharyngeal carcinoma?

Background and purposeTo evaluate the prognostic value of gross primary tumor volume (GTV-P) in nasopharyngeal carcinoma (NPC) patients treated with intensity modulated radiotherapy (IMRT).Methods and materialsA total of 694 nonmetastatic and histologically proven NPC patients who underwent IMRT were retrospectively reviewed. Samples were split randomly into a training set (n = 232) and a test set (n = 462) to analysis. The receiver operating characteristic (ROC) curves were calculated to identify the cut-off point and test the prognostic validity of the GTV-P. The correlations between GTV-P and the American Joint Committee on Cancer (AJCC) disease stages were also analyzed.ResultsThe 5-year disease-free survival (DFS), overall survival (OS), local relapse-free survival (LRFS) and distant metastasis-free survival (DMFS) rates for NPC patients with GTV-P < 19 vs. ⩾19 ml were 94.9% vs. 64.8%, 97.0% vs. 76.4%, 98.2% vs. 92.5% and 97.1% vs. 75.2%, respectively (all P < 0.05) in all patients. Multivariate analysis indicated GTV-P was an independent prognostic factor. The ROC curve verified that the predictive ability of T classifications was improved when combined with GTV-P (P < 0.001).ConclusionsGTV-P is an independent prognostic indicator for treatment outcome after IMRT, and significantly improves the prognostic validity of T classifications in NPC.