Tamoxifen is a medication used to treat or prevent breast cancer. One of its side effects is an increased risk of uterine cancer. But for many people, the benefits of tamoxifen may outweigh its risks.
Uterine cancer is a type of cancer that starts in the uterus. Certain factors can increase your risk of developing uterine cancer. One of these is taking the medication tamoxifen.
Keep reading to learn more about tamoxifen and how taking it can affect your risk of developing uterine (endometrial) cancer.
You take tamoxifen orally. It can come in the form of a tablet or as an oral solution. The brand names for tamoxifen include Nolvadex and Soltamox.
Tamoxifen is approved by the Food and Drug Administration (FDA) for the following uses:
- to treat metastatic breast cancer that’s estrogen receptor (ER)-positive
- to treat early ER-positive breast cancer after breast cancer surgery
- to lower the risk of breast cancer after surgery for ductal carcinoma in situ (DCIS), an early, noninvasive form of breast cancer
- to help prevent breast cancer in women who have a higher breast cancer risk
Tamoxifen is taken over a period of several years. Most people will take it for
While tamoxifen inhibits estrogen activity in breast tissue, it can stimulate estrogen receptors in other parts of the body, including the uterus.
Estrogen can prompt cells in the lining of your uterus (the endometrium) to multiply. Over time, increased estrogen activity may increase your risk of developing uterine cancer.
Various studies have estimated that tamoxifen users have a
While taking tamoxifen can increase your risk of uterine cancer, tamoxifen-associated cancers are still uncommon. For example, the risk of developing endometrial cancer due to tamoxifen is about 1 in 500.
People who develop tamoxifen-associated uterine cancer can sometimes have a poorer outlook. This is because uterine cancers that are associated with tamoxifen can be
The duration of tamoxifen use can also play a role. Generally speaking, people who take tamoxifen for longer may not have as good an outlook if they do develop uterine cancer.
For many people, the benefits of tamoxifen far outweigh its risks. For example, the
- death due to breast cancer was 15% and 12.2% in those who took the drug for 5 and 10 years, respectively
- breast cancer recurrence was 25.1% and 21.4% in individuals who took tamoxifen for 5 and 10 years, respectively
- endometrial cancer was 1.6% and 3.1% in those taking tamoxifen for 5 years and 10 years, respectively
For people with additional risk factors for developing uterine cancer, the risks of tamoxifen may not be OK for them. It’s important to discuss the risks and benefits of tamoxifen with your oncologist and healthcare team.
What are the side effects of tamoxifen?
Some of the common side effects of tamoxifen include:
In addition to an increased risk of uterine cancer, tamoxifen has other possible serious side effects, such as:
- deep vein thrombosis (DVT)
- pulmonary embolism (PE)
- problems with the eyes
- problems with the liver
What are other risk factors for uterine cancer?
In addition to taking tamoxifen, other risk factors for uterine cancer include:
- older age
- a family history of uterine cancer
- a personal history of breast cancer or ovarian cancer
- endometrial hyperplasia
- other factors affecting estrogen levels, such as:
- using estrogen-only hormone replacement therapy
- having polycystic ovary syndrome (PCOS) or certain types of ovarian tumors
- never being pregnant
- health conditions like obesity and type 2 diabetes
- previous radiation therapy to the pelvic area
What’s the outlook for uterine cancer?
Your outlook can depend on many factors, such as the type of cancer, its stage, and your age and overall health.
According to the
People who are taking or have taken tamoxifen are at a higher risk for developing uterine cancer. These cancers may be more aggressive or diagnosed at later stages than uterine cancers in someone who has never taken tamoxifen.
But generally speaking, tamoxifen-associated uterine cancers are still uncommon. The benefits of tamoxifen may outweigh its risks for some people.
If tamoxifen is part of your breast cancer treatment plan, be sure to discuss its associated risks with your oncologist.