Mother had breast cancer 4.5 yrs ago & it’s not returned. She may start taking Evista for osteoporosis. I understand that it mimics estrogen & has not been shown to stimulate growth in breast tissue. Have there been any studies that state differently?

Raloxifene is in a class of drugs called the selective estrogen receptor modulators (SERMs) and is currently only approved for the prevention of osteoporosis. These drugs selectively block certain estrogen receptors while activating others. Women have estrogen receptors in their heart, bones, reproductive organs, breast, brain, and liver. Each month, in the presence of estrogen, estrogen receptors in the breast and uterus stimulate growth and division in cells to prepare for a possible pregnancy.

Up to 50-75% of the cancers that originate in the breast or reproductive organs will have estrogen receptors. In this case, estrogen becomes a danger because it signals for the tumor to grow. Blockage of these receptors can stop or slow tumor growth in most cases. Ideally, the perfect drug would block breast and endometrial (found in the uterus) receptors, while activating them in the bone, to prevent osteoporosis; in the brain to prevent hot flashes; and in the liver and cardiovascular system to prevent cardiovascular disease and cholesterol abnormalities. Raloxifene blocks receptors in the brain, breast, and reproductive organs while activating them in the bone and cardiovascular system. This principle may be used to treat estrogen receptor positive cancers of the breast and uterus. There is good evidence to suggest it is effective in the treatment of breast cancer. Clinical studies that are evaluating Raloxifene, such as the STAR Trial (study of Raloxifene and Tamoxifen) are still in progress and the prospective results are unknown. The Multiple Outcomes of Raloxifene Evaluation (MORE) osteoporosis trial showed up to a 70% reduction in breast cancer incidence. A closer look at this study found that Raloxifene was not evaluated with respect to use for cancer and did not adequately control potential bias that may affect results concerning the treatment of cancer. No studies have found that Raloxifene will cause estrogen receptor positive tumors to grow.