• Anne W M Lee, W T Ng, W M Hung, C W Choi, Raymond Tung, Y H Ling, Peter T C Cheng, T K Yau, Amy T Y Chang, Samuel K C Leung, Michael C H Lee, and Soren M Bentzen.
• Department of Clinical Oncology, Pamela Youde Nethersole Eastern Hospital, Hong Kong. awmlee@ha.org.hk
• Int. J. Radiat. Oncol. Biol. Phys. 2009 Mar 15; 73 (4): 1121-8.

PurposeTo retrospectively analyze the factors affecting late toxicity for nasopharyngeal carcinoma.Methods And MaterialsBetween 1998 and 2003, 422 patients were treated with a conformal technique with 2-Gy daily fractions to a total dose of 70 Gy. Conventional fractionation (5 fractions weekly) was used in 232 patients and accelerated fractionation (6 fractions weekly) in 190 patients. One hundred seventy-one patients were treated with the basic radiotherapy course alone (Group 1), 55 patients had an additional boost of 5 Gy in 2 fractions (Group 2), and 196 patients underwent concurrent cisplatin-based chemotherapy (Group 3).ResultsThe 5-year overall toxicity rate was significantly greater in Group 3 than in Group 1 (37% vs. 27%, p = 0.009). Although the overall rate in Group 2 was not elevated (28% vs. 27%, p = 0.697), a significant increase in temporal lobe necrosis was observed (4.8% vs. 0%, p = 0.015). Multivariate analyses showed that age and concurrent chemotherapy were significant factors. The hazard ratio of overall toxicity attributed to chemotherapy was 1.99 (95% confidence interval, 1.32-2.99, p = 0.001). The mean radiation dose to the cochlea was another significant factor affecting deafness, with a hazard ratio of 1.03 (95% confidence interval, 1.01-1.05, p = 0.005) per 1-Gy increase. The cochlea that received >50 Gy had a significantly greater deaf rate (Group 1, 18% vs. 7%; and Group 3, 22% vs. 14%).ConclusionThe therapeutic margin for nasopharyngeal carcinoma is extremely narrow, and a significant increase in brain necrosis could result from dose escalation. The significant factors affecting the risk of deafness included age, concurrent chemoradiotherapy, and greater radiation dose to the cochlea.

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