Duration of tamoxifen use and the risk of contralateral breast cancer in BRCA1 and BRCA2 mutation carriers
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Women with a mutation in BRCA1 or BRCA2 face a lifetime risk of breast cancer of approximately 80 %. Tamoxifen treatment of the first cancer has been associated with a reduction in the risk of a subsequent contralateral cancer. We studied 1,504 women with a known BRCA1 or BRCA2 mutation, 411 women with bilateral breast cancer (cases) and 1,093 women with unilateral breast cancer (controls) in a matched case–control study. Control women were of similar age and had a similar age of diagnosis of first breast cancer as the cases. For each woman who used tamoxifen, the starting and stopping dates were abstracted and the duration of tamoxifen use was calculated. Three hundred and thirty-one women had used tamoxifen (22 %); of these 84 (25 %) had completed four or more years of tamoxifen, the remainder stopped prematurely or were current users. For women with up to 1 year of tamoxifen use, the odds ratio for contralateral breast cancer was 0.37 (95 % CI 0.20–0.69; p = 0.001) compared to women with no tamoxifen use. Among women with 1–4 years of tamoxifen use the odds ratio was 0.53 (95 % CI 0.32–0.87; p = 0.01). Among women with four or more years of tamoxifen use the odds ratio was 0.83 (95 % CI 0.44–1.55; p = 0.55). Short-term use of tamoxifen for chemoprevention in BRCA1 and BRCA2 mutation carriers may be as effective as a conventional 5-year course of treatment.
KeywordsBreast cancer Tamoxifen Oophorectomy BRCA1 BRCA2
We would like to thank study coordinators Adriana Valentini, Marcia Llacuachaqui, and Alejandra Ragone, as well as Jennifer Ng, Kristi De Buono, Kate Bisnaire, Dina Nikitina, Anneli Loo, Bita Khorram, Dina Gordon, Courtney May, Michelle Jones, Jose Miguel Lozano and Linda Steele who helped with the data collection and data entry. Supported by grants from the Canadian Breast Cancer Research Alliance and the Canadian Cancer Society Research Initiative and an ICARE grant IBG09-34198 awarded to T. Pal. SLN is the Morris and Horowitz Families Endowed Professor, and the work was supported by NIH R01 CA74415.
Conflict of interest
The authors declare no conflicts of interest.
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