OBJECTIVE: The effect of postoperative external beam radiation in MOnon-small cell lung cancer resected with curative intention was evaluatedin a randomized trial. METHODS: In 155 patients (121 males, 34 females;mean age: 59 years) 105 lobectomies, 12 bilobectomies and 38pneumonectomies with radical lymph node dissection to the contralateralside were carried out. Histology revealed squamous cell (n = 68), adeno- (n= 53), large cell (n = 21), adenosquamous (n = 6) or bronchioloalveolartype (n = 7) carcinomas. The pathologic stages T1 (n = 38), T2 (n = 89), T3(n = 28); NO (n = 39), N1 (n = 67), and N2 (n = 49) were evenly distributedbetween the two treatment groups: group A (72 patients) had no furtheroncologic treatment, while group B (83 patients) had external beamradiation to the mediastinum (50-56 Gy, 8 or 23 MeV photons, 2 Gy/day, 5days a week) beginning 4 weeks after the operation. RESULTS: The overall5-year survival rate of the whole collective was 24.1% without anysignificant difference between the radiotherapy group B (29.7%) and thecontrol group A (20.4%) (log-rank test: P > 0.05). The overall 5-yearrecurrence-free survival rate was 20.1%, with no difference between groupsB and A (radiotherapy: 22.7, controls: 15.6%, long-rank test: P > 0.05).There was no difference in the incidence of distant metastases (externalbeam radiation: n = 32; controls: n = 38). The rate of local recurrences atthe bronchial stump or in the mediastinum, however, was significantlyreduced in the radiotherapy group (n = 5) compared with 17 in the controls(P < 0.01 chi-square test). A multivariate analysis confirmed theindependent influence of postoperative radiotherapy on the incidence oflocal recurrence. CONCLUSIONS: External radiation of the mediastinum inradically resected non-small cell lung cancer reduces the risk of localrecurrence, but has no influence on distant metastastic spread and overallsurvival.