Metcalfe 2014.

Methods	Retrospective cohort study
Participants	Family history/risk ‐ BRCA1/BRCA2 mutation carrier families
Interventions	482 women from BRCA1/BRCA2 mutation carrier families diagnosed with S I or II BC from 1975‐2000, age < 66, and were mutation carriers or untested CRRM = 146 No CRRM = 336
Outcomes	BC incidence
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Free of selection bias?	High risk	Some of the CBC was diagnosed within 1‐2 months of original diagnosis of BC, less than the commonly used second new BC diagnoses at ≤ 6 months, and more correctly should be classified as bilateral BC. This classification then could have overstated the incidence of CBC in the no‐CRRM group. There are also some discrepancies in reporting the date of diagnosis. In the Methods section it says "...diagnosis of SI or SII BC at age 65 or less, between 1975 and 2008". But in the results section it says “The women were given a diagnosis between 1977 and 2009 …”. Also in the Methods section it is stated that “…54 (14%) were not tested.” But in the Strengths and Limitations section it is stated that “…53 women included in this study who did not undergo genetic testing …”. This small discrepancy in numbers could have a major impact on the long‐term results due to the small denominator on which these are based.
Free of performance bias?	Low risk	Medical records were obtained from the hospital where the CRRM was performed.
Free of detection bias?	Low risk	Medical treatment records and pathology documents were reviewed.
Free of attrition bias?	Unclear risk	This report is a follow‐up to Metcalfe 2004a that reported on 482 women (CRRM = 146; no CRRM = 336), 92 more than in the update. This report does not say what happened to the 92 participants in the 2004a report although in the update, women who had breast‐conserving surgery were excluded, which may explain the difference.