Influence of intensity-modulated radiotherapy on tumor regression in nasopharyngeal carcinoma

Objective: To retrospectively analyze the influence of intensity-modulated radiotherapy (IMRT) on tumor regression in primary nasopharyngeal carcinoma (NPC). Methods: 272 patients with NPC received radical radiotherapy alone, 196 by IMRT with a total treatment time of 6 weeks, and 76 by bilateral field conventional radiotherapy (CRT) with the total treatment time of 7 weeks. Results: By the end of radiotherapy, the primary tumor and neck lymph node residual rates of the IMRT group were 36.7% and 44.2%, respectively, both significantly higher than those of the GRT group (21.1% and 26.6%, χ² =6.15, 3.99, P<0.05). Three months after the radiotherapy, residual lesions were observed at the nasopharynx or neck lymph nodes in 12 of the IMRT group, with a residual rate of 6.1%, not significantly different from that of the CRT group (9.2%, 7/76). The 12 residual lesions of the IMRT group all vanished completely 4-9 months after the radiotherapy. Conclusions: There is an obvious difference in regressive mode between IMRT and CRT technique in NPC treatment. At the end of IMRT, the tumor residual rate is slightly increased.However, the delivered dose of gross tumor volume (GTV) is sufficient,and the boost dose should not be delivered indiscreetly. (authors)