Backgrounds: With the excellent local control in T1 to T3 nasopharyngeal carcinoma (NPC) treated with intensity modulated radiotherapy (IMRT), the importance of toxicities is increasingly being recognised. This retrospective propensity score analysis sought to assess whether moderate dose reduction compromised long-term outcome compared with standard dose in T1-3 NPCs. Materials and Methods: A total of 266 patients (67 female, 199 male) with a median age of 50 years between June 2011 and June 2015 were analysed. All were treated with IMRT, with or without systemic chemotherapy. The prescription radiation dose to gross tumor is 70Gy/2.12Gy/33F in our institution. Results: With a median follow-up time of 50 months, the 5-year loco-regional failure-free survival (LRFS) and overall survival (OS) were 93.5% and 81.8%, respectively. 32 patients received radiation dose less than prescription dose, with a median dose of 63.6Gy (53-67Gy). Another 234 patients received exactly the prescription dose of 70Gy. Propensity scores were computed (32 patients treated with de-escalated dose and 64 patients with standard dose), there was no significant difference in 5-year LRFS and 5-year OS between the two groups (92.5% and 91.7% with standard dose; 82.1% and 85.7% with de-escalation dose; p=0.863 for LRFS and 0.869 for OS). No independent prognostic factor was associated with loco-regional failure in univariate analysis. Conclusions: T1-3 nasopharyngeal carcinoma presenting with superior locoregional control, a moderately reduced dose (about 10%) delivered with IMRT resulted in comparable prognosis to those with prescription dose of 70Gy.
Keywords: IMRT; Nasopharyngeal carcinoma; Radiation dose; dose de-escalation.
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