Researchers Investigate Link Between Hormone Replacement Therapy and Ovarian Cancer
A newly published study conducted by Swedish researchers finds a possible link between hormone replacement therapy (HRT) and an increased risk of ovarian cancer. Hormone replacement therapy (estrogen plus progestin) and estrogen replacement therapy (ERT, estrogen alone) are commonly prescribed to help treat menopausal symptoms and prevent the degenerative bone disease, osteoporosis. In recent years, researchers have focused on whether HRT increases the risk of breast cancer and whether it truly prevents heart disease, as previously thought. Now, the focus on HRT and ERT is widening to include other potential side effects, including the risk of ovarian cancer. In the Swedish study, women who took ERT or HRT (with intermittent progestin use) faced a slightly higher ovarian cancer risk. The risk was greater with prolonged hormone use (more than 10 years). However, the researchers say the study results do not warrant any changes in ERT/HRT prescribing guidelines and should not cause worry among short-term hormone users (one to four years).
Hormone replacement therapy (HRT) contains synthetic forms of estrogen and/or progesterone (called progestin) designed to replace a woman's depleting hormone levels at menopause. Depleting hormone levels can cause symptoms such as hot flashes, mood swings, and night sweats. HRT, or estrogen replacement therapy (ERT), is also effective at treating osteoporosis, which commonly affects post-menopausal women and can lead to debilitating bone fractures. In addition, HRT is thought to help prevent heart disease, although recent studies suggest that past data on HRT and heart disease may be flawed.
Previous research, including a study of over 200,000 women conducted by researchers from the American Cancer Society, has found that using ERT (estrogen alone) for 10 years or longer increases the risk of ovarian cancer, although the risk appears to be small--approximately 2% compared to 1% without using ERT. In the newly published study, Tomas Riman, MD of Falu Hospital, Falun, Sweden and his colleagues set out to investigate the effect of HRT (estrogen plus progestin) on ovarian cancer risk.
To conduct the study, Dr. Riman and his team used Swedish cancer registries to identify women between the ages of 50 and 74, 3,899 of whom were cancer-free and 655 of whom had been diagnosed with a certain type of ovarian cancer called epithelial carcinoma that develops on the surface of the ovary. The researchers sent questionnaires to the women to learn about their hormone therapy use and overall risk of ovarian cancer, based on family history, etc.
Dr. Riman and his colleagues found that women who used ERT (estrogen alone) and HRT (with intermittent use of progestin) were more likely than non-hormone users to develop ovarian cancer. Women who used a type of HRT whereby they continuously took progestin with the estrogen did not have a higher than average risk of ovarian cancer. The risk of ovarian cancer among ERT and intermittent HRT users was relatively small and translated into approximately two to three more cases of ovarian cancer per 1,000 women. (Approximately 1% of women are diagnosed with ovarian cancer in the general population). The risk of developing ovarian cancer was greater among the women who used hormones for more than 10 years.
While the study provides more information on hormone use and ovarian cancer risk, the researchers say the results should be interpreted cautiously and do not warrant changes to current hormone guidelines. Little research has been completed to date that examines HRT (estrogen plus progestin) and the risk of ovarian cancer, and large studies are needed to better understand how one may impact the other.
The study also confirms the 2001 American Cancer Society study that found ERT (estrogen alone) to increase ovarian cancer risk among long-term users. Experts are not certain why ERT increases the risk of ovarian cancer, but they do know that estrogen causes ovarian cells to produce at faster than normal rates. The more times a cell divides, the higher the chances that it will replicate an abnormal copy, which could result in cancer if the abnormal copy controls cell growth. ERT has also been associated with an increased risk of endometrial cancer (cancer of the uterine lining), but using combination hormone therapy (with progestin) counteracts this risk.
Dr. Riman and his colleagues say that their study results should not impact short-term hormone users who need relief from bothersome menopausal symptoms. However, women are encouraged to discuss hormone use with their physicians and fully weigh the benefits and risks based on their individual medical situation.
Approximately 23,400 cases of ovarian cancer are diagnosed each year in the United States. Like many cancers, ovarian cancer can be highly treatable if detected in early stages. However, many cases of ovarian cancer are not diagnosed until advanced stages. This is because the symptoms of ovarian cancer can be very subtle ("silent") or unnoticeable until the disease has progressed significantly. Symptoms of ovarian cancer include pelvic/abdominal pain, gastrointestinal problems, frequent urination, changes in bowel habits, weight gain or loss, pain during sexual intercourse, fatigue, leg pain, or unusual vaginal bleeding. If any of these symptoms persist, women should inform their physicians and undergo clinical examination.