7528 Background: We conducted a prospective randomized phase III trial comparing induction chemotherapy followed by concurrent chemoradiotherapy (CCRT) versus immediate CCRT to evaluate whether the addition of induction chemotherapy would result in improved survival. Methods: Patients with unresectable stage III NSCLC, ECOG PS 0–1, and weight loss up to 10% were eligible. They were randomized to receive either induction chemotherapy followed by CCRT (arm A) or immediate CCRT (arm B) after stratification for stage (T4N0–2, T1–3N3, T4N3, and stage IIIA), histology (squamous vs non-squamous), and SCLN positivity. Induction chemotherapy consisted of two cycles of gemcitabine (1,000 mg/m2 D1, D8) and cisplatin (70 mg/m2 D1) q 21days. Chemotherapy during CCRT consisted of 6 cycles of weekly paclitaxel (50 mg/m2) and cisplatin (20 mg/m2). Radiation therapy performed with hypofractionated scheme (2.2 Gy/fraction, once a day) and total dose was 66 Gy. Irradiated volume encompassed gross tumor plus 1.0 cm margin. Results: Between March 2003 and June 2006, 134 patients were enrolled. 92% of patients were male and 60% were age 60 or older. Objective tumor response was obtained in 38% after induction chemotherapy. Response rates after completion of CCRT were 72% (95% CI, 61%–83%) on arm A and 79% (95% CI, 69%–89%) on arm B. Grade 3/4 toxicities during induction chemotherapy consisted mainly of neutropenia (11%/3%). During CCRT, grade 3/4 neutropenia was noted in 8%/5% (arm A) versus in 8%/0% (arm B), grade 3 anemia was 8% vs 0%, grade 3 thrombocytopenia 5% vs 0%, and grade 3 esophagitis 16% vs 16%. At median follow-up of 28 months, median survival was 12.6 months (95% CI, 8.6–16.7 months) on arm A versus 18.2 months (95% CI, 11.7–24.8 months) on arm B (P=0.18). Two year survival estimates was 25% (15%–35%) and 43% (31%–55%), respectively. Median progression free survival was 7.5 months (95% CI, 5.6–9.4 months) on arm A and 11.6 months (95% CI, 9.6–13.6 months) on arm B (P=0.04). Conclusions: The addition of induction chemotherapy to CCRT failed to increase the survival of unresectable stage III NSCLC over immediate CCRT. Moreover, the progression free survival was inferior to immediate CCRT. No significant financial relationships to disclose.