How Breast Cancer Treatments Affect Fertility
Chemotherapy, hormonal treatments (such as tamoxifen) and targeted treatments (such as trastuzumab/Herceptin) and newer agents like PARP inhibitors and CDK4/6 inhibitors may affect fertility differently. Surgery and radiation rarely affect fertility.
Chemotherapy’s Impact on Fertility
Chemotherapy can damage or destroy eggs, increasing your risk of infertility immediately or years after treatment ends. Your age and the type and total amount of chemotherapy contribute to infertility risk. The younger you are and the less chemotherapy you have had, the more likely you are to remain fertile. Women under age 35 are most likely to have their periods return after treatment.
Talk to your healthcare team about your individual risk based on your specific treatment plan, age, and other factors.
Tamoxifen and Herceptin Impact on Fertility
Tamoxifen is a hormonal treatment given to patients with estrogen receptor positive (ER+) breast cancer. Evidence on tamoxifen's direct effect on ovarian reserve is scarce and controversial. Tamoxifen may interfere with childbearing because of the duration of the treatment—usually five to 10 years—during which time women should not get pregnant.
Because taking tamoxifen in early pregnancy may cause birth defects, it will be important not to be on tamoxifen if you are trying to become pregnant. After two years of treatment, some women may choose to go off tamoxifen to get pregnant, then resume tamoxifen treatment after giving birth. Recent studies, including the POSITIVE trial, show that temporarily interrupting endocrine therapy (up to 2 years in the study) to attempt pregnancy does not increase the risk of breast cancer recurrence. Talk to your doctor about whether this is a reasonable option for you.
Herceptin or trastuzumab is a targeted treatment for HER2+ breast cancer. HER2-directed agents have not yet demonstrated significant ovarian toxicity, and there are limited data on their effect on fertility. You should not get pregnant while taking trastuzumab and should wait at least seven months after completing trastuzumab treatments before trying to get pregnant. Trastuzumab treatments are usually given regularly for one year.