Menopause and Cancer

Menopause is the transition in a woman's life when her ovaries stop producing eggs, her menstrual periods become irregular before stopping completely, and her body decreases its production of the hormones, estrogen, and progesterone. Menopause usually occurs in a woman's mid-40s to mid-50s and may last for months or years. Symptoms of menopause include hot flashes and night sweats, vaginal dryness, sleeplessness, decreased sex drive, and mood swings.

Cancer risk and menopause

Menopause itself is not a risk factor for cancer, however, because the risk of most types of cancer increases with age, postmenopausal women (women whose menstruation has ceased for 12 months) are more likely than premenopausal women to develop cancer simply because they are older. Aging also increases the risk of developing osteoporosis (bone loss), arthritis, heartand vascular disease, memory loss, and even dementia.

The age at which a woman reaches menopause does affect her chances of developing certain cancers. Women who reach menopause after age 55, especially if they began menstruating before age 12, are at increased risk for developing ovarian, breast, and uterine cancers. Both uterine and breast cancers are affected by lifetime exposure to estrogen. Because estrogen levels are highest during a woman's reproductive years, a longer menstrual history means more lifetime estrogen exposure and a greater risk of breast and uterine cancers. The risk of ovarian cancer is related to the total number of times a woman ovulates and, therefore, a longer menstrual history (more total ovulations) increases ovarian cancer risk.

Cancer treatment and menopause

The timing of cancer treatment and types of therapy used also impact menopause. For example, almost half of premenopausal women experience menopausal symptoms as a result of breast cancer or its treatment. Cancer treatments that affect the functioning of the ovaries can cause early or premature menopause (menopause that occurs before age 40). Menopause caused by medical treatment is referred to as medical (or surgical) menopause and occurs quickly, as opposed to natural menopause that occurs over several years giving the body time to adapt gradually to decreasing hormone levels. Because the hormonal changes that occur with medical menopause tend to happen suddenly, the symptoms tend to be more severe.

Radiation treatment to the pelvis and some types of chemotherapy can damage the ovaries, causing or premature menopause. Some younger women find that their periods return after stopping cancer treatment, but ovarian function is less likely to return in women over age 40. Even if cancer treatment does not cause menopause immediately, it may cause menopause to start earlier than it otherwise would have. On the other hand, an oophorectomy (surgical removal of the ovaries), used in the treatment and prevention of ovarian, uterine, and vaginal cancers, does immediately lead to medical menopause because the source for estrogen and progesterone has been removed.

Hormonal therapy is used to manage breast cancer tumors that are estrogen-and/or progesterone receptor positive, meaning that they use estrogen to fuel tumor growth. The most common hormone therapy drug, tamoxifen (Nolvadex), reduces the risk of breast cancer recurrence in women already treated, as well as reduces the risk of breast cancer in women with an increased risk, by blocking the action of estrogen. However, tamoxifen can cause side effects similar to the symptoms of menopause, especially hot flashes. Premenopausal women taking tamoxifen may find that their periods become lighter and less regular, or their periods may stop completely. Periods may return after treatment with tamoxifen ends, but this is less likely in women who are closer to their natural menopausal age. Women who have already reached menopause may have a recurrence of menopausal symptoms when they start tamoxifen. Other side effects of tamoxifen include a small increased risk of both uterine cancer and risk of blood clots.

Cancer and hormone replacement therapy

For years, hormone replacement therapy (HRT) was considered standard treatment for relieving menopausal symptoms such as hot flashes and vaginal dryness, as well as helping to prevent osteoporosis and heart disease. HRT usually involves a combination of estrogen and progestin (a synthetic form of progesterone)—also know as "combined HRT." Estrogen given alone increases the risk of uterine cancer and is only prescribed to women who have had a hysterectomy (removal of the uterus). However, in recent years, the use of HRT has become controversial because of evidence suggesting an increased risk of breast cancer in women taking combined HRT.

A reliable source for information on HRT comes from the Women's Health Initiative, a large, randomized clinical trial sponsored by the National Institutes of Health (NIH). Findings from the study of estrogen-plus-progestin HRT showed that women wishing to lessen menopausal symptoms who were taking estrogen plus progestin had an increased risk of breast cancer, heart attack, stroke, and blood clots, and a decreased risk of colorectal cancer and bone fractures.

Due to these increased risks, many doctors are now recommending that women, especially those at higher than normal risk for developing breast cancer, avoid estrogen-plus-progestin HRT or only take low doses for a short period to lessen severe menopausal symptoms. Because of the increased breast cancer risk, estrogen-plus-progestin HRT is not usually recommended for women with a history of breast cancer.

The evidence surrounding HRT is controversial and studies in the area are ongoing. The risks and benefits of HRT are different for each woman and she should discuss the pros and cons of HRT with her doctor before deciding whether HRT is right for her. For more information on other kinds of treatment for menopausal symptoms, read Menopausal Symptoms: Women.

Men and menopausal symptoms

While true menopause only occurs in women, some men treated for prostate cancer experience some of the same menopausal symptoms that women experience. Prostate cancer growth is driven by male sex hormones known as androgens, primarily testosterone. Hormone therapy, also called androgen ablation or androgen deprivation therapy, reduces levels of testosterone to slow the growth of the cancer, either through surgery, with surgical castration (removal of the testicles), or through the use of drugs that turn off the function of the testicles.

Lack of testosterone can cause menopausal-like symptoms such as hot flashes (experienced by up to 75% of men on hormone therapy), irritability, decreased sex drive, fatigue, osteoporosis, and erectile dysfunction (inability to achieve or maintain an erection). These symptoms may occur in men without prostate cancer as part of the aging process and can be treated with medications to increase testosterone levels. Because the goal of hormone therapy is to decrease testosterone levels, these medications are not considered a good option for treating menopausal symptoms in men with prostate cancer. For more information on managing menopausal symptoms in men, read Hormone Deprivation Symptoms: Men.

Additional resources

National Institute on Aging: Menopause

National Institutes of Health: Menopausal Hormone Therapy Information

National Cancer Institute: Understanding Estrogen Receptors, Tamoxifen, and Raloxifene