Post-mastectomy megavoltage radiotherapy: the Oslo and Stockholm trials

Abstract

The ability of adjuvant radiotherapy to prevent distant metastasis and to prolong survival in patients with early breast cancer is much debated. The paper presents a joint analysis of long-term results (13-16 years' follow-up) from the Oslo and Stockholm randomised trials of post-operative megavoltage radiotherapy versus surgery alone. Among node-positive patients there was a significant 37% relative reduction of distant metastases with radiation (P less than 0.01) and an overall survival difference in favor of the irradiated patients which corresponded with a 22% relative reduction of deaths of borderline significance (P less than 0.06). No significant benefit with radiation in terms of distant metastasis-free survival or overall survival was observed among node-negative patients. The results show that effective local treatment can prevent distant dissemination in some patients and contradict the contention that node-positive breast cancer invariably is a systemic disease already at primary diagnosis.