7550 Background: In the CALGB Study Cis with Gem followed by concomitant chemoradiation for inoperable LA-NSCLC was effective, however with significant toxicity (E. Vokes et al; JCO 20: 2002). The aim of this study was to improve tolerability by reducing the Gem dose during radiotherapy and adding one cycle of induction chemotherapy. Methods: Patients with histological proven stage IIIA and IIIB NSCLC were included in this study from 8/04 to 9/07. All patients were to receive 3 induction cycles (21 days) of Cis 80 mg/m2 d1 plus Gem 1250 mg/m2 over 30 minutes d1, 8. After a 3 weeks rest period, 2 cycles of concomitant chemoradiation Cis 80 mg/m2 d1, Gem 300 mg/m2 d1, 8 and RTX (about 60 Gy; 5 times 1,8 Gy fractions / week) were given. Results: A total of 49 patients, median age 63.4 yrs, 73.5% male, with Karnofsky performance status 80/85/90/100: 16.3% / 2.0% / 49.0% / 32.7% were entered. Disease stage IIIA/IIIB: 28.6% / 71.4%. Median dose intensity during chemoradiation Gem 98.4%, Cis 99.0% and radiation median total dose was 63 Gy. Number of grade 3/4 toxicities during induction chemotherapy (N=49): neutropenia 9/9, thrombocytopenia 4/1. Acute grade 3/4 toxicities during chemoradiation phase (N=31): neutropenia 4/0, thrombocytopenia 5/1, radiation esophagitis 4/0 and radiation pneumonitis 1/0. No toxic death. Tumor Response Rate of enrolled patients was 22 (44.9%) (95% CI: 30.7–59.8). Conclusions: Concurrent Cis Gem chemoradiation after Cis Gem induction is an active treatment for LA-NSCLC with managable toxicity. [Table: see text]