From the Guidelines
If you're taking tamoxifen for breast cancer and develop ovarian cysts, you should discuss this with your doctor but it's not necessarily cause for immediate alarm. Tamoxifen, while effective for breast cancer treatment, can sometimes stimulate the ovaries and lead to the formation of ovarian cysts as a side effect, as seen in various studies 1. These cysts are typically benign and may resolve on their own. However, monitoring is important because tamoxifen slightly increases the risk of certain health issues, such as endometrial cancer, deep vein thrombosis, and cataracts, as indicated in the NSABP Breast Cancer Prevention Trial 1.
Key points to consider:
- The risk of invasive endometrial cancer is higher in women over 50 years old taking tamoxifen, with a risk ratio of 4.01 compared to placebo 1.
- The risk of deep vein thrombosis and pulmonary embolism also increases with tamoxifen use, particularly in women over 50 years old 1.
- Regular gynecological check-ups, including pelvic exams and possibly ultrasounds, are recommended for women on tamoxifen therapy to monitor for any potential issues.
- If you experience symptoms like pelvic pain, bloating, or changes in menstrual patterns, inform your doctor promptly.
- The benefits of tamoxifen for breast cancer treatment generally outweigh these risks, but your healthcare provider may need to evaluate whether to continue tamoxifen or consider alternative treatments depending on your specific situation, cancer type, and overall health profile, as suggested by the results of the IBIS-I trial and the STAR trial 1.
From the FDA Drug Label
Ovarian cysts have also been observed in a small number of premenopausal patients with advanced breast cancer who have been treated with tamoxifen. The presence of ovarian cysts in patients taking tamoxifen may be a concern, but there is no direct evidence to suggest that ovarian cysts increase the risk of breast cancer. However, tamoxifen has been reported to cause menstrual irregularity or amenorrhea, which may be related to its effect on the ovaries.
- The incidence of ovarian cysts is not well established, and the relationship between ovarian cysts and breast cancer risk is not clear.
- Patients receiving tamoxifen should be monitored for any changes in their menstrual cycle or ovarian function.
- Annual gynecological examinations are recommended for patients receiving or who have previously received tamoxifen 2.
From the Research
Ovarian Cysts in Tamoxifen-Treated Women with Breast Cancer
- Ovarian cysts are a common side effect of tamoxifen treatment in women with breast cancer, with a frequency of 11% to 34.3% reported in various studies 3, 4, 5, 6.
- The development of ovarian cysts is related to high estrogen levels, younger age, and the absence of high-dose chemotherapy 6.
- Most ovarian cysts associated with tamoxifen treatment are simple and may resolve spontaneously or with discontinuation of tamoxifen 4, 5.
- However, malignancy needs to be ruled out, and surgery may be required in some cases 5.
Risk Factors for Ovarian Cysts in Tamoxifen-Treated Women
- Younger age: Women under 50 years old are more likely to develop ovarian cysts while taking tamoxifen 6.
- High estrogen levels: Women with high serum estrogen levels are more likely to develop ovarian cysts 6.
- Absence of high-dose chemotherapy: Women who have not received high-dose chemotherapy are more likely to develop ovarian cysts 6.
- Menstrual cycle: Women who are still having a menstrual cycle while taking tamoxifen have a high chance of developing ovarian cysts 6.
Management of Ovarian Cysts in Tamoxifen-Treated Women
- Gonadotropin-releasing hormone agonist (GnRHa) therapy may be an effective treatment for ovarian cysts in tamoxifen-treated women 3.
- Discontinuation of tamoxifen may also lead to resolution of ovarian cysts 4.
- Surgery may be required in some cases to rule out malignancy or to manage persistent or growing cysts 5.