A Cochrane review [Abstract] 1 [withdrawn from publication] included 40 studies with a total of 20 000 subjects. A reduction of approximately two-thirds in local recurrence was seen in all trials, largely independent of the type of patient or type of radiotherapy (8.8% vs 27.2% local recurrence by year 10). Hence, to assess effects on breast cancer mortality of substantially better local control, results from all trials were combined.
Breast cancer mortality was reduced, but other, particularly vascular, mortality was increased, and overall 20-year survival was 37.1% with radiotherapy versus 35.9% control. There was little effect on early deaths, but logrank analyses of later deaths indicate that, on average after year 2, radiotherapy reduced annual mortality rates from breast cancer by 13.2% but increased those from other causes by 21.2%. Nodal status, age, and decade of follow-up strongly affected the ratio of breast cancer mortality to other mortality, and hence affected the ratio of absolute benefit to absolute hazard from these proportional changes in mortality.
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