Endometrial cancer is cancer that starts in the endometrium, or inner lining of the uterus (the hollow, pear-shaped organ that is part of your reproductive system). It is sometimes also referred to as uterine cancer. Endometrial cancer usually occurs after natural menopause, with 60 being the average age at diagnosis.
The most common symptom of endometrial cancer is abnormal bleeding or discharge that isn’t part of your regular period. If you’ve already gone through menopause (no periods for one full year), having any bleeding or discharge again could be a warning sign. Other symptoms include unusual pelvic pain or pressure, difficult or painful urination, and pain during intercourse.
The breast cancer treatment tamoxifen (sometimes called by its brand name, Nolvadex) increases the risk of developing endometrial cancer, but not nearly enough to outweigh its benefits against breast cancer in most women. This risk occurs because of the way tamoxifen works: Even as it acts against the growth-promoting effects of the female hormone estrogen in breast tissue, it acts like an estrogen in other tissues, such as the bones and the uterus. This can be good news for the bones because estrogen helps preserve bone density, but it may slightly increase the risk of cancer in the uterus. According to the American Cancer Society, the risk of developing endometrial cancer from tamoxifen is about 1 in 500 — a small risk, but higher than that for women in the general population. Tamoxifen also slightly increases the risk of uterine sarcoma, a cancer that begins in the muscle of the uterine wall.
Tamoxifen belongs to a class of medications known as selective estrogen response modifiers (SERMs). Another SERM called Fareston (chemical name: toremifine) has been found to increase the risk of endometrial hyperplasia, or the overgrowth of cells lining the uterus. Hyperplasia itself is not cancer but can sometimes develop into cancer. Evista (chemical name: raloxifene), another SERM used to lower the risk of breast cancer in high-risk women, does not have estrogen-like effects on the uterus and does not increase endometrial cancer risk.
Managing endometrial cancer risk
If tamoxifen or Fareston is recommended a part of your treatment plan, see your gynecologist (or family medicine doctor, if he or she provides your gynecologic care) for a baseline visit and pelvic exam. Together you can discuss any other risk factors you may have for endometrial cancer, such as:
- having taken postmenopausal hormone replacement therapy (HRT)
- high-fat diet
- lack of exercise
- never having had children
- early menstruation and/or late onset of menopause
- polycystic ovarian syndrome (or PCOS, a hormonal disorder often characterized by the development of many cysts in the ovaries)
- hereditary nonpolyposis colorectal cancer syndrome, or HNPCC (an inherited condition that raises risk for many types of cancers, including colorectal, endometrial, and ovarian, among others)
Tamoxifen and Fareston typically aren’t recommended if you have a history of endometrial hyperplasia.
If you have multiple risk factors for endometrial cancer, you and your doctor can weigh the risks and benefits of taking tamoxifen or Fareston for you as an individual. If you’re postmenopausal and concerned about endometrial cancer risk, you may want to take an aromatase inhibitor instead. Aromatase inhibitors reduce the amount of estrogen in the body overall, instead of blocking its effects.
If you’re taking tamoxifen or Fareston, do your best to take control of the risk factors for endometrial cancer that can be changed:
- lose weight as needed
- eat a healthy, low-fat diet
- exercise regularly
- if you have diabetes, keep it under control
You and your doctor also can set a schedule for regular pelvic exams that makes sense for you. See your doctor promptly in between visits if you have any abnormal vaginal bleeding, discharge, or pelvic pain. There isn’t a reliable screening test for endometrial cancer, and it usually doesn’t show up in the results of a routine Pap test (the removal and examination of a cell sample from the cervix, or lower neck of the uterus). Because endometrial cancer almost always causes symptoms, though, it’s usually caught at an early stage and treated successfully.
If your doctor ever suspects endometrial cancer, he or she will perform an endometrial biopsy by removing a sample of tissue from the uterine lining for examination under a microscope. The usual treatment for endometrial cancer is hysterectomy (removal of the uterus) and removal of the ovaries and fallopian tubes. Radiation therapy also may be recommended. Still, keep in mind that the risk of developing endometrial cancer due to tamoxifen is still quite low.
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