Post-mastectomy megavoltage radiotherapy: the Oslo and Stockholm trials

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.