Long-Term Use of Hormone Replacement Therapy Increases Risk of Breast Cancer

Long-Term Use of Hormone Replacement Therapy Increases Risk of Breast Cancer.

According to results recently published in the Journal of the American Medical Association, recent use of long-term hormone replacement therapy is associated with increased risk of breast cancer, particularly lobular breast cancer.

Breast cancer is a common malignancy among women with almost 200,000 new cases diagnosed each year in the United States. Breast cancer develops when cells in the breast grow abnormally. Lobular breast cancer arises from the milk-producing glands in the breast. Invasive lobular breast cancer breaks through the walls of the milk glands and invades adjacent fatty tissue. From here, it may spread throughout the body. In contrast, lobular cancer in situ never penetrates the milk glands’ walls. While it remains isolated, physicians believe it predisposes a woman to invasive breast cancer in the future. Non-lobular breast cancer is breast cancer arising within breast tissue, but outside the milk glands. Treatment of breast cancer usually consists of surgery and/or systemic therapy (e.g., radiation, chemotherapy and/or hormone therapy).

Hormone replacement therapy (HRT) is typically prescribed for women during menopause. Menopause is a natural phase of maturing womanhood, during which ovaries produce significantly less estrogen, ovulation ceases and menstruation ends. For many women, menopause has uncomfortable side effects. Hot flashes, sleep disturbances, depression, mood swings and anxiety may affect the menopausal woman. Additionally, menopause may also be accompanied by increased urinary tract infections, incontinence, vaginal discomfort due to a lack of estrogen-based lubrication and decreased bone density. HRT has been effectively used to mitigate these side effects and is widely prescribed for women experiencing these unpleasant symptoms of menopause. Despite these benefits, however, some clinical studies suggest that HRT use, particularly for extended periods of time, may increase risk of developing breast cancer.

Researchers at the Fred Hutchinson Cancer Research Center conducted a clinical trial investigating whether recent use of long-term HRT was associated with increased rates of breast cancer, particularly specific types of breast cancer. Recent long-term use was defined as use of HRT five out of six years prior to a diagnosis of breast cancer. Researchers examined computerized pharmacy records for HRT prescriptions of 705 post-menopausal women with invasive breast cancer and compared them against 692 healthy women. The researchers screened for two types of HRT: estrogen alone and estrogen plus progestin.

Researchers found a 70% increase in all types of breast cancer with recent long-term use of estrogen alone or estrogen plus progestin HRT. The risk of non-lobular breast cancer increased 50% in women with recent long-term HRT use and the risk of lobular breast cancer was increased three-fold. Current use of combination (estrogen and progestin) HRT appeared to increase the risk four-fold for developing breast cancer.

Results from this study suggest that recent long-term use of HRT appears to significantly increase the risk of developing breast cancer. Individuals who are currently using HRT or who have done so in the recent past may wish to speak with their physician regarding the risks and benefits of HRT and appropriate screening measures.

(Journal of the American Medical Association, Vol 287, pp 734-741, 2002)

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