BACKGROUND: Early findings on the use of tamoxifen or raloxifene as prophylaxis against breast cancer have been mixed; we update available data and overview the combined results. METHODS: All five randomised prevention trials comparing tamoxifen or raloxifene with placebo were included. Relevant data on contralateral breast tumours and side-effects were included from an overview of adjuvant trials of tamoxifen versus control. FINDINGS: The tamoxifen prevention trials showed a 38% (95% CI 28-46; p<0.0001) reduction in breast-cancer incidence. There was no effect for breast cancers negative for oestrogen receptor (ER; hazard ratio 1.22 [0.89-1.67]; p=0.21), but ER-positive cancers were decreased by 48% (36-58; p<0.0001) in the tamoxifen prevention trials. Age had no apparent effect. Rates of endometrial cancer were increased in all tamoxifen prevention trials (consensus relative risk 2.4 [1.5-4.0]; p=0.0005) and the adjuvant trials (relative risk 3.4 [1.8-6.4]; p=0.0002); no increase has been seen so far with raloxifene. Venous thromboembolic events were increased in all tamoxifen studies (relative risk 1.9 [1.4-2.6] in the prevention trials; p<0.0001) and with raloxifene. Overall, there was no effect on non-breast-cancer mortality; the only cause showing a mortality increase was pulmonary embolism (six vs two). INTERPRETATION: The evidence now clearly shows that tamoxifen can reduce the risk of ER-positive breast cancer. New approaches are needed to prevent ER-negative breast cancer and to reduce the side-effects of tamoxifen. Newer agents such as raloxifene and the aromatase inhibitors need to be evaluated. Although tamoxifen cannot yet be recommended as a preventive agent (except possibly in women at very high risk with a low risk of side-effects), continued follow-up of the current trials is essential for identification of a subgroup of high-risk, healthy women for whom the risk-benefit ratio is sufficiently positive.
RCT Entities:
BACKGROUND: Early findings on the use of tamoxifen or raloxifene as prophylaxis against breast cancer have been mixed; we update available data and overview the combined results. METHODS: All five randomised prevention trials comparing tamoxifen or raloxifene with placebo were included. Relevant data on contralateral breast tumours and side-effects were included from an overview of adjuvant trials of tamoxifen versus control. FINDINGS: The tamoxifen prevention trials showed a 38% (95% CI 28-46; p<0.0001) reduction in breast-cancer incidence. There was no effect for breast cancers negative for oestrogen receptor (ER; hazard ratio 1.22 [0.89-1.67]; p=0.21), but ER-positive cancers were decreased by 48% (36-58; p<0.0001) in the tamoxifen prevention trials. Age had no apparent effect. Rates of endometrial cancer were increased in all tamoxifen prevention trials (consensus relative risk 2.4 [1.5-4.0]; p=0.0005) and the adjuvant trials (relative risk 3.4 [1.8-6.4]; p=0.0002); no increase has been seen so far with raloxifene. Venous thromboembolic events were increased in all tamoxifen studies (relative risk 1.9 [1.4-2.6] in the prevention trials; p<0.0001) and with raloxifene. Overall, there was no effect on non-breast-cancer mortality; the only cause showing a mortality increase was pulmonary embolism (six vs two). INTERPRETATION: The evidence now clearly shows that tamoxifen can reduce the risk of ER-positive breast cancer. New approaches are needed to prevent ER-negative breast cancer and to reduce the side-effects of tamoxifen. Newer agents such as raloxifene and the aromatase inhibitors need to be evaluated. Although tamoxifen cannot yet be recommended as a preventive agent (except possibly in women at very high risk with a low risk of side-effects), continued follow-up of the current trials is essential for identification of a subgroup of high-risk, healthy women for whom the risk-benefit ratio is sufficiently positive.
Authors: Garnet L Anderson; Rowan T Chlebowski; Aaron K Aragaki; Lewis H Kuller; JoAnn E Manson; Margery Gass; Elizabeth Bluhm; Stephanie Connelly; F Allan Hubbell; Dorothy Lane; Lisa Martin; Judith Ockene; Thomas Rohan; Robert Schenken; Jean Wactawski-Wende Journal: Lancet Oncol Date: 2012-03-07 Impact factor: 41.316
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Authors: Ciric To; Eun-Hee Kim; Darlene B Royce; Charlotte R Williams; Ryan M Collins; Renee Risingsong; Michael B Sporn; Karen T Liby Journal: Cancer Prev Res (Phila) Date: 2014-05-09
Authors: Nandita Das; Richard N Baumgartner; Elizabeth C Riley; Christina M Pinkston; Dongyan Yang; Kathy B Baumgartner Journal: J Cancer Surviv Date: 2015-04-26 Impact factor: 4.442