Prospective phase II trial of concomitant boost radiotherapy for stage II nasopharyngeal carcinoma: an evaluation of response and toxicity.

Introduction: Stage II nasopharyngeal carcinoma (NPC) treated with conventionally fractionated radiotherapy results in loco-regional control of around 80%. This report aims to document the outcome of Stage II NPC patients treated with external beam radiotherapy delivered using an accelerated concomitant boost (C-Boost) schedule.

Methods And Materials: Twenty-five 1997 AJCC Stage II NPC patients were enrolled and analyzed in this preliminary report. The primary tumor and clinically involved nodes received a total dose of 72 Gy in 42 fractions. C-Boost for gross disease consisted of 18 Gy in 12 fractions commencing on day 19 and was delivered at least 6 hours after the first dose. Patients were assessed for response, survival, and toxicity.

Results: With a median follow-up of 24 months, only one patient had pathologically confirmed local recurrence, necessitating IMRT. Two developed distant metastases for which they received chemotherapy. One died from systemic disease after refusing treatment for persistent neck lymphadenopathy. Two-year loco-regional control rates, overall survival and disease-free survival rates were 96%, 96%, and 88%, respectively. All patients experienced some degree of acute and/or late toxicity. However, the toxicity profile was comparable to that seen following standard fractionation. Acute or late toxicities directly attributable to C-Boost were not observed.

Conclusion: This C-Boost radiotherapy regimen administers a substantially higher biologically effective dose compared with conventional radiation schedules. Preliminary locoregional control and survival rates are promising with no significant acute and/or late toxicities.