Treatment of nasopharyngeal carcinoma using simultaneous modulated accelerated radiation therapy via helical tomotherapy: a phase II study.

Background. The aim of the study was to evaluate short-term safety and efficacy of simultaneous modulated accelerated radiation therapy (SMART) delivered via helical tomotherapy in patients with nasopharyngeal carcinoma (NPC). Methods. Between August 2011 and September 2013, 132 newly diagnosed NPC patients were enrolled for a prospective phase II study. The prescription doses delivered to the gross tumor volume (pGTV(nx)) and positive lymph nodes (pGTV(nd)), the high risk planning target volume (PTV1), and the low risk planning target volume (PTV2), were 67.5 Gy (2.25 Gy/F), 60 Gy (2.0 Gy/F), and 54 Gy (1.8 Gy/F), in 30 fractions, respectively. Acute toxicities were evaluated according to the established RTOG/EORTC criteria. This group of patients was compared with the 190 patients in the retrospective P70 study, who were treated between September 2004 and August 2009 with helical tomotherapy, with a dose of 70-74 Gy/33F/6.5W delivered to pGTV(nx) and pGTV(nd). Results. The median follow-up was 23.7 (12-38) months. Acute radiation related side-effects were mainly problems graded as 1 or 2. Only a small number of patients suffered from grade 4 leucopenia (4.5%) or thrombocytopenia (2.3%). The local relapse-free survival (LRFS), nodal relapse-free survival (NRFS), local-nodal relapse-free survival (LNRFS), distant metastasis-free survival (DMFS) and overall survival (OS) were 96.7%, 95.5%, 92.2%, 92.7% and 93.2%, at 2 years, respectively, with no significant difference compared with the P70 study. Conclusions. SMART delivered via the helical tomotherapy technique appears to be associated with an acceptable acute toxicity profile and favorable short-term outcomes for patients with NPC. Long-term toxicities and patient outcomes are under investigation.