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POSITIVE news about pregnancy and breast cancer

Pausing hormone therapy results in healthy pregnancies and babies for most women



Fertility is an important concern of young women with breast cancer, yet it is often neglected in clinical practice and in research. Breast cancer can occur at any age, sometimes before having any or all planned children. Conversations about cancer treatment between doctors and patients often fail to include discussion of fertility. Women are left with questions about if or how treatment will affect their fertility. Opportunities to preserve fertility are seldom discussed at all.

Living Beyond Breast Cancer’s 2020 study of the changing needs of young women with breast cancer, also presented at SABCS 2022, addressed this topic. We compared the results of our 2020 survey to a 2012 survey we conducted. Little had changed in 8 years. In 2020, only 49% of survey respondents discussed fertility with their doctors and 28% initiated the conversation, compared with 46% and 29%, respectively, in 2012.

Endocrine therapies such as tamoxifen are the standard of care for premenopausal women with early-stage hormone receptor-positive breast cancer. Women typically stay on these therapies for 5 to 10 years. Some of these drugs interfere with ability to get pregnant or have been linked to birth defects. Women trying to get pregnant take a break from hormone therapy in order to do so. Until now, little has been known about the safety of this — the risk of breast cancer relapse or the potential for healthy pregnancies and births.


The POSITIVE clinical trial was a single-arm study that looked primarily at breast cancer-free interval, and secondly at pregnancy and birth outcomes. The study group had up to 2 years to attempt pregnancy, conceive, deliver, and breastfeed following a 3-month washout period when they went off the endocrine therapy.

The international study included 518 women with Stage I-III ER+ breast cancer, age 42 or younger, who had been treated with endocrine therapy in the form of a SERM, SERM plus ovarian function suppression, or aromatase inhibitor for 18 to 30 months. Sixty-two percent of women in the trial were also treated with neoadjuvant chemotherapy. Slightly more than half of the women opted for breast-conserving surgery; 45% had mastectomies.

The research team matched data from the SOFT and TEXT trials. to the study group to create a control group. They found no statistically significant difference in terms of breast cancer development between the study group and the control group. This was true for women who became pregnant and those who did not.

The pregnancy results were favorable as well. Seventy-four percent of women had at least one pregnancy, of whom 86% had a live birth (64% of all women in the trial). Some women achieved pregnancy with the help of reproductive technology. Only 11% of women experienced complications of any kind, mostly hypertension or diabetes. Of the 317 women who had live births, 62% reported breastfeeding. The percentage of birth defects was low (2%), consistent with the general population. By 48 months, 76% of women had resumed endocrine therapy.

The median follow-up for this group was 41 months. These women are still being followed, so longer-term data may be available in the future.

What these findings mean for you

This is exciting news for women with early-stage breast cancer who are interested in pregnancy. One of the key takeaways is the importance of talking with your cancer care team about fertility. It is never too early to talk with your oncologist if you have been diagnosed with breast cancer and may want to get pregnant in the future. You may want to seek advice from a reproductive specialist as well.

While these results are very favorable, longer-term follow-up is needed to track how long these women remain cancer-free over time and how those numbers compare to women who do not interrupt endocrine therapy.


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