McDonnell 2001.

Methods	Case series
Participants	Family history/risk ‐ all with a first BC, who had a family history of breast or ovarian cancer Participants underwent CRRM between 1960 and 1993 388 = pre‐menopausal 357 = post‐menopausal
Interventions	CRRM (41% subcutaneous, 59% total) = 745 Comparison group: simulated from age‐adjusted life tables presuming no CRRM
Outcomes	BC incidence
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Free of selection bias?	High risk	The analysis did not sufficiently control for confounding factors (i.e. histology or stage of primary tumor).
Free of performance bias?	Low risk	Participants identified through search of Surgical Index Recording System for all participants having a CRRM from 1960‐1993.
Free of detection bias?	Low risk	Medical record information was available for all participants.
Free of attrition bias?	Low risk	Median length of follow‐up was 10 years. Questionnaires completed for 90.3% of the participants