Several conditions of the breast commonly occur before the development of breast cancer. Some of these conditions, such as intraductal hyperplasia with atypia and lobular carcinoma in situ (LCIS), are microscopic risk factors that can indicate that a woman is at increased risk of developing breast cancer.
Tamoxifen has been shown to decrease breast cancer risk in women with specific premalignant breast cancges in the P1 and P2 NSABP trials. Results from the Breast Cancer Prevention Trial (BCPT) have shown that women at increased risk for breast cancer are less likely to develop the disease if they take tamoxifen. Tamoxifen is approved for reducing breast cancer risk in high-risk women.
The MORE trial for osteoposrosis suggested that raloxifen decreases risks of breast cancer as well. Whether raloxifene or tamoxifene is superior in cancer prevention in women at risk is the subject on an oanging trial, Study of Tamoxifen and Raloxifene (STAR) for the Prevention of Breast Cancer in Postmenopausal Women, NCT00003906. The Study of Tamoxifen and Raloxifene (STAR) trial, found that raloxifene worked as well as tamoxifen in reducing the risk of invasive breast cancer, although it didn’t have the same protective effect against non-invasive cancer (DCIS or LCIS). Raloxifene did, however, have lower risks of certain side effects such as uterine cancer and blood clots in the legs or lungs, compared to tamoxifen (although the risk of blood clots was still higher than normal).
Aromatase inhibitors, such as Aromsyn, are being investigated for prevention in women with DCIS . Most DCIS lesions are likely to be ER-positive. Results from the MAP.3 trial found that the aromatase inhibitor Aromasin (chemical name: exemestane) was good at lowering breast cancer risk in high-risk postmenopausal women, but weakened bones. The research was published Feb. 7, 2012 online in The Lancet Oncology. NCCN on p. BRISK-B cites this study only for post0menopausal women with a Gil risk of 1.7% in 5 years or LCIS. Routine use of aromatase inhibitors for prevention of DCIS is not yet been recommended by any guideline, to my knowledge.
Trevor J. Powles Re: Tamoxifen for Prevention of Breast Cancer: Report of the National Surgical Adjuvant Breast and Bowel Project P-1 Study
J. Natl. Cancer Inst. 91: 730.
R. T. Chlebowski, N. Col, E. P. Winer, D. E. Collyar, S. R. Cummings, V. G. Vogel III, H. J. Burstein, A. Eisen, I. Lipkus, and D. G. Pfister
American Society of Clinical Oncology Technology Assessment of Pharmacologic Interventions for Breast Cancer Risk Reduction Including Tamoxifen, Raloxifene, and Aromatase Inhibition
J. Clin. Oncol., August 1, 2002; 20(15): 3328 – 3343.
Fabian, Carol Tamoxifen or Raloxifene in Postmenopausal Women for Prevention of Breast Cancer: A Tale of Two Choices Counterpoint Cancer Epidemiol Biomarkers Prev 2007 16: 2210-2212
Monica Morrow Refining the Use of Endocrine Therapy for Ductal Carcinoma in Situ JCO April 20, 2012 vol. 30 no. 12 1249-1251