According to results recently published in the journal Cancer, the use of hormone replacement therapy (HRT) may not increase the risk of cancer recurrences in patients with hormone-negative 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 and is often estrogen-based, but can also contain progesterone alone or in combination with estrogen. 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. Due to the apparent increase in breast cancer risk with the use of HRT, patients and physicians have questioned whether the use of HRT could increase the risk of developing a cancer recurrence in women previously diagnosed with breast cancer.

Some breast cancers have an overabundance of estrogen and/or progesterone receptors and are stimulated to grow by the presence of estrogen and/or progesterone, which are two main female hormones. Women whose cancer has an overabundance of these receptors are referred to as having hormone receptor-positive breast cancer. Women whose cancer has not demonstrated an overabundance of these receptors are referred to as having hormone receptor-negative breast cancer. Researchers speculated that hormone-receptor negative and positive breast cancer may respond differently to HRT.

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Researchers from the MD Anderson Cancer Center conducted a clinical study comparing cancer recurrences in postmenopausal women diagnosed with stages I-II breast cancer. Patients in this study had hormone-receptor negative or hormone-receptor unknown breast cancer, 56 of whom were treated with long-term HRT with estrogen and 243 comparable women who did not receive HRT. Women with hormone-receptor negative breast cancer were considered cancer-free for at least two years prior to HRT and women with hormone-receptor unknown breast cancer were considered cancer-free for at least 10 years prior to HRT. Approximately 5 years following HRT, no breast cancer recurrences occurred in the group treated with HRT and 3.6% of patients developed a new cancer in the opposite breast. New or recurrent breast cancer occurred in 13.5% of women who were not treated with HRT. Cancer-free survival was similar between the two groups of patients.

These results indicate that HRT may not increase the risk of developing a cancer recurrence in postmenopausal patients with hormone-receptor negative or hormone-receptor unknown early stage breast cancer. Patients with hormone-receptor negative, early-stage breast cancer with postmenopausal symptoms may wish to discuss the risks and benefits of HRT with their physician.

Reference: Vassilopoulou-Sellinn R, Cohen DS, Hortobagyi GN, et al. Estrogen replacement therapy for menopausal women with a history of breast carcinoma. Results of a 5-year, prospective study.

Cancer. 2002;95: 1817-1826.

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