This study presented outcomes of a prospective multicenter trial with an early closure. Twenty-eight patients with stage II or III unresectable NSCLC were treated with hypofractionated proton therapy at 2.5-4 Gy per fraction to a total 60 Gy(RBE) with concurrent chemotherapy. After a median follow-up of 31 months, the 1- and 3-year OS rates were 89% and 49%; and PFS rates were 58% and 32%, respectively. No acute grade 3 or higher esophagitis occurred. Only 14% developed a grade 3 or higher radiation-related pulmonary toxicity.