, Volume 146, Issue 2, pp 421-427
Date: 21 Jun 2014

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.

Other members of the Hereditary Breast Cancer Clinical Study Group who contributed to the study: David Euhus, Judy Garber, Gad Rennert, Kevin Sweet, Ruth Gershoni-Baruch, Christine Rappaport, Edmond Lemire, Lovise Maehle, Dominique Stoppa-Lyonnet, Mary Daly, Sofia Merajver, Ava Kwong, Louise Bordeleau, Carey A. Cullinane, Eitan Friedman, Wendy McKinnon, Marie Wood, Daniel Rayson, Wendy Meschino, Jane McLennan, Josephine Wagner Costalas, Robert E. Reilly, Tuya Pal, Susan Vadaparampil, Kenneth Offit, Mark Robson, Noah Kauff, Jan Klijn, David Euhus, Claudine Isaacs, Fergus Couch, Cezary Cybulski, Tomasz Byrski, Ania Jakubowska, Seema Panchal, Sonia Nanda, Aletta Poll, Kelly Metcalfe, Barry Rosen, Susan Randall Armel, Albert Chudley, Gareth Evans, Joanne Blum, Beth Karlan, Dana Zakalik, John Lunn, Talia Donenberg, Barbara Pasini, Raluca N Kurz, Taya Fallen.