Early stage nasopharyngeal carcinoma: radiotherapy dose and time factors in tumor control

OBJECTIVE: To evaluate radiotherapy dose and length of treatment in thecontrol of early stage nasopharyngeal carcinoma (NPC) treated with acombination of external radiotherapy and brachytherapy, MATERIALS &METHODS: We reviewed the records of 133 patients with early stagenasopharyngeal carcinoma (stage I or II, AJC/UICC staging system) whoreceived definitive radiotherapy in Chang Gung Memorial Hospital from 1979to 1991. The median follow-up time was 7.1 years with a minimum of 2 years.All patients were treated with megavoltage external radiotherapy to thenasopharynx area (63-72 Gy) followed by high dose rate intracavitarybrachytherapy (5-16.5 Gy in one to three fractions, spaced 1-2 weeksapart). The median total dose and time of irradiation was 75 Gy (69.8-81.4Gy) and 11.6 weeks (7.8-20 weeks) respectively. Survival analysis was usedto examine the effect of several variables on prognosis. RESULTS: The5-year rates were 86.4% for local control, 84.7% for disease free survival,88.5% for actuarial survival and 84.2% for overall survival. The treatmentgroup (combination of time and dose of irradiation) was the most importantprognostic factor according to Cox's proportional hazard model. Patientsreceiving radiation at a total dose of < or = 75 Gy completed in < 12weeks showed the best prognosis. CONCLUSION: Treatment time and totaltreatment dose are both important factors in treating early stage NPC.Decreasing the total radiation time to < 12 weeks and not exceeding aradiation dose of 75 Gy gave the best results.