Primary tumor volume of nasopharyngeal carcinoma: Significance for survival

Objectives To elucidate the effect of primary tumor volume (PTV) on treatment outcomes in patients with nasopharyngeal carcinoma (NPC) who were treated with radiotherapy or concurrent chemoradiotherapy. The TNM staging system developed by American Joint Committee of Cancer (AJCC) is universally used and accepted but its prediction of prognosis in NPC receives a lot of challenge. Primary tumor volume had been reported to have close relationship with prognosis of head and neck cancer. We may predict prognosis of NPC with PTV. Methods From 1999 to 2006, 91 patients with newly diagnosed NPC who were treated with radiotherapy or CCRT were enrolled in the study. Computed tomography-derived or magnetic resonance-derived primary tumor volume was calculated. The correlation between AJCC disease stage, primary tumor volume and disease-specific survival were analyzed. Multivariate analyses using the Cox proportional hazard model was performed. Results The median primary tumor volume for the whole series was 11.39 ml (range 1.25–166.58 ml). The median primary tumor volume was 2.69 ml in T1 disease, 10.14 ml in T2 disease, 15.41 ml in T3 disease, and 26.69 ml in T4 disease. Hazard ratio increased with tumor volume, ranging from 5.91 (95% confidence interval (95% CI) 1.13–26.43) for tumor volumes between 20 ml and 40 ml, and 15.72 (95% CI, 3.82–61.05) for tumor volumes >40 ml. With both tumor volume and T classification in the same Cox regression model, only tumor volume remained statistically significant in the prognosis of NPC. Conclusion Primary tumor volume has closer relationship with survival rates of patients with NPC. Calculation of primary tumor volume may be further considered to improve the current staging system.