A phase II study of adaptive two-step intensity-modulated radiation therapy (IMRT) with chemotherapy for loco-regionally advanced nasopharyngeal cancer (JCOG1015).

Background: A phase II study of adaptive two-step intensity-modulated radiotherapy (IMRT) with chemotherapy for nasopharyngeal cancer (NPC) (JCOG1015) was conducted to evaluate the efficacy and safety.
Methods: Patients aged 20-75 years with stages II-IVB NPC were enrolled. As adaptive two-step IMRT, computed tomography planning was performed twice before IMRT for the initial plan of 46 Gy/23 fractions and during treatment for the boost plan of 24 Gy/12 fractions with a total dose of 70 Gy. Chemotherapy (cisplatin 80 mg/m ² /3-weeks × 3 courses) was administered concurrently with IMRT, followed by adjuvant chemotherapy (cisplatin at 70 mg/m ² with 5-FU 700 at mg/m ² for 5 days/4 weeks × 3 courses).
Results: Between 2011 and 2014, 75 patients were enrolled from 12 institutions. The 3-year overall survival (OS) for the 75 patients was 88%, and the upper and lower limits of the 95% CI of 78%-94% were higher than the expected 3-year OS of 75% for the target population adjusted by the actual proportion of stage II:III:IV = 21%:44%:35%. The 3-year progression-free survival (PFS) and loco-regional PFS were 71% [59-80%] and 77% [66-85%], respectively. Although no grade 4-5 late toxicities were observed, 15 patients (20%) developed grade 3 late toxicities. Grade 2 xerostomia was noted in 26%, 12%, and 9% at 1, 2, and 3 years after starting IMRT, respectively.
Conclusions: Adaptive two-step IMRT for NPC demonstrated an excellent 3-year OS with acceptable toxicities. This method may be one treatment option for locally advanced NPC.