Thirty-four year follow up of patients with breast cancer in clinical trial of postoperative radiotherapy.

An extended follow up to a maximum of 34 years was carried out on a series of 1461 patients who had been entered into a randomised clinical trial comparing immediate postoperative radiotherapy (treated group) with an optional delayed radiotherapy policy (watched group) after Halsted radical mastectomy for operable breast cancer. Long term survival was compared separately in patients with negative and positive axillary nodes and in two periods when different techniques of radiotherapy were used. No significant differences were noted in survival overall or in any subgroup. In patients with negative axillary nodes treated in the earlier period when the "quadrate" radiotherapy technique was used, however, the difference in survival was of borderline significance (p = 0.052), to the benefit of the watched group. Because of the large numbers of patients entered and the long follow up any possible harmful or beneficial effect of immediate postoperative radiotherapy would have been apparent in the results of this trial. The absence of any such effect implies that postoperative radiotherapy given to prevent or delay local recurrence of breast cancer is unlikely to be associated with a detectable effect on survival.