Postoperative radiotherapy in breast cancer--long-term results from the Oslo study

The long-term results of a randomized clinical trial evaluating the effect of postoperative radiotherapy as an adjuvant to radical mastectomy are presented. There were 1115 patients including 27 protocol deviants. The follow-up time is 11-20 years. In the first part a conventional roentgen unit was used, and in the second part a 60Co unit, with considerably increased dosage and altered treatment plan. Both types of radiation techniques lowered the incidence of loco-regional recurrences significantly, but had no significant influence on the overall survival. The relapse-free survival was significantly improved by 60Co radiation in Stage II patients, but was unaffected by radiation in the other subgroups. Regarding survival, Stage II patients with medially located tumors seemed to benefit more from 60Co radiation than those with lateral tumors. A significant increase in the number of deaths caused by myocardial infarction was observed in Stage I patients having 60Co radiation, indicating that the radiation dose to the heart is of significance.