It can, but this depends largely on what type of therapy you take and how long you take it. Let me explain: There are two types of HRT, estrogen, and a combination of estrogen and progestin. Because estrogen has been used to raise the incidence of uterine cancer, it is used primarily for women who no longer have a uterus. The estrogen/progestin therapy is usually reserved fro women who still have a uterus. The latter has been shown to increase a woman's risk of breast cancer more significantly than estrogen alone. The Breast Cancer Demonstration Project found that women's risk of breast cancer went up by about 1% percent for every year that they took estrogen alone, and for every year that they took estrogen plus progestin, their risk went up by about 8%.
The real risk with HRT is prolonged use-the longer a woman uses it the greater her risk. For example, if a woman takes estrogen with progestin for ten years, her risk of breast cancer will be 80% higher than if she had never used hormones. For both types of therapy, however, this increase in risk begins to drop after hormone use stops and eventually returns to that of someone who has never used hormones.
Women should not take HRT for prolonged periods of time. There are many wonderful alternatives which can help her alleviate painful symptoms without increasing her breast cancer risk, including natural hormone replacements, lifestyle and dietary modification.