Background and purpose: To assess the therapeutic gain achieved by accelerated fractionation for non-keratinizing/undifferentiated nasopharyngeal carcinoma (NPC).
Materials and methods: During January 1994 to October 1997, 325 patients were treated to a total dose of 66 Gy in 33-37 fractions: 167 (irradiated before mid-January 1996) with 5 daily fractions (CF) and subsequent 158 with 6 daily fractions (AF) per week. Their median treatment times were 46 and 39 days, respectively. Additional boost to parapharyngeal extension had been given to 181 and Cisplatin-based chemotherapy to 57 patients (24 concurrent with radiotherapy).
Results: The AF group had significantly higher progression-free rate than the CF group (74 vs. 63% at 3 years, P=0.02 by the log-rank test). However, the difference in disease-specific survival (86 vs. 80%, P=0.39) and overall survival (81 vs. 78%, P=0.9) did not reach statistical significance. Strongly significant improvement in local failure-free rate was achieved for patients with T3-4 tumors (87 vs. 62%, P<0.01). Multivariate analyses showed that fractionation was an independent significant factor for overall progression: hazard ratio=0.63, 95% confidence interval: 0.41-0.98, P=0.04. Among the 268 patients treated with radiotherapy alone, those treated by AF had significantly higher incidence of acute reaction grade > or=3 (72 vs. 13%, P<0.01). However, all patients completed the scheduled dose without excessive prolongation, and no significant increase in late complications was observed (20 vs. 15% at 3 years, P=0.19).
Conclusions: The current analyses suggested that acceleration to 6 daily fractions per week could significantly improve the progression-free rate for NPC without excessive late toxicity. Improvement in local control was confined to T3-4 tumors.