Effects of radiotherapy and of differences in the extent of surgery for early breast cancer on local recurrence and 15 year survival

__Background:__ In early breast cancer, variations in local treatment that substantially affect the risk of locoregional recurrence could also affect long-term breast cancer mortality. To examine this relationship, collaborative metaanalyses were undertaken, based on individual patient data, of the relevant randomised trials that began by 1995. __Methods:__ Information was available on 42 000 women in 78 randomised treatment comparisons (radiotherapy vs no radiotherapy, 23 500; more vs less surgery, 9300; more surgery vs radiotherapy, 9300). 24 types of local treatment comparison were identified. To help relate the effect on local (ie, locoregional) recurrence to that on breast cancer mortality, these were grouped according to whether or not the 5-year local recurrence risk exceeded 10% (10%, 25 000 women). __Findings:__ About three-quarters of the eventual local recurrence risk occurred during the first 5 years. In the comparisons that involved little (10%) differences, however, 5-year local recurrence risks were 7% active versus 26% control (absolute reduction 19%), and 15-year breast cancer mortality risks were 44·6% versus 49·5% (absolute reduction 5·0%, SE 0·8, 2p<0·00001).