Patients may receive radiotherapy when clinically indicated. Estimation of the 5-year disease-free survival in the control arm is 72%. The experimental arm is expected to increase the 5-year disease-free survival by 7% (up to 79%). With an alpha error of 0.05 and 80% power, 592 patients per arm are needed. Assuming a 17% post-randomization drop-out, 691 patients per arm are needed.