Tamoxifen for Breast Cancer
Several conditions of the breast commonly occur before the development of breast cancer. One such condition is Ductal Carcinoma in Situ(DCIS). Some of these conditions, such as intraductal hyperplasia with atypia and Lobular Carcinoma In-Situ (LCIS), are not in themselves pre-cancerous but 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 changes 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 osteoporosis suggested that raloxifen decreases risks of breast cancer as well. Whether raloxifen or tamoxifen is superior in cancer prevention in women at risk was the subject on a trial, Study of Tamoxifen and Raloxifen (STAR) for the Prevention of Breast Cancer in Postmenopausal Women, NCT00003906. The Study of Tamoxifen and Raloxifen (STAR) trial, found that raloxifen 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). Raloxifen 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 Aromasyn, are being investigated for prevention in women with DCIS. Most DCIS lesions are likely to be ER-positive and anti-estrogens like Aromasyn(exemestane) might be effective in reducing the risk of breast cancer. Recent results from the MAP.3 trial found that the aromatase inhibitor Aromasyn (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.
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