Definitive IMRT alone with reduced prophylactic nodal irradiation for Early-Stage Oropharyngeal Cancer: JCOG1208.

Abstract

Prospective data on definitive radiotherapy alone for early-stage oropharyngeal cancer (OPC) are limited. JCOG1208 evaluated intensity-modulated radiation therapy (IMRT) alone with reduced prophylactic nodal irradiation in selected patients with early-stage OPC. JCOG1208 was a prospective, multi-institutional, single-arm study that enrolled patients aged 20-80 years with T1-2 N0-1 M0 OPC of the tonsil, base of tongue, or soft palate according to the UICC 7th edition. Concurrent chemotherapy was not permitted. Patients received two-step adaptive IMRT to 70 Gy in 35 fractions, including 46 Gy to the initial target volumes followed by a 24 Gy boost. The primary endpoint was 3-year overall survival (OS), with a predefined threshold of 80 %. Fifty-seven patients were enrolled. Median follow-up was 6.8 years. Three-year OS was 93.0 % (95 % CI, 82.4-97.3 %), and 5-year OS was 87.6 % (95 % CI, 75.8-93.9 %). Five-year progression-free survival and loco-regional progression-free survival were 77.0 % and 78.8 %, respectively. No recurrences occurred solely within omitted prophylactic nodal regions. Most patients with progression had p16-negative/unknown disease and/or smoking history. Grade ≥ 3 late adverse events were observed in one patient. IMRT alone with reduced prophylactic nodal irradiation showed encouraging long-term survival in selected patients with early-stage OPC, with no failures solely within omitted prophylactic nodal regions. However, progression patterns suggest that careful patient selection based on p16/HPV status and smoking history is essential when considering radiotherapy alone. UMIN-CTR UMIN000014274.