Pregnancy After Breast Cancer Is Safe, Landmark Study Says

Jan. 5, 2023 – Planning to have a child is a life-changing decision. For women who have survived breast cancer, the consideration is even more complex. 

For a long time, there wasn’t definitive research on how pregnancy impacted the likelihood of whether their cancer would return. But initial results from a new study show women who paused protective post-cancer therapies to get pregnant had no increased risk of their cancer coming back. Nearly 3 in 4 women in the study got pregnant, and 64% had a live birth. 

One of those “babies after breast cancer” was Ronin Andrade, who turns 1 on Jan. 6. His mother, Shayla Johnson, of Assonet, MA, plans to bake him an Instagram-worthy cake. She participated in the research trial.

“As a woman, I felt like I’ve lost my breasts, I’ve lost my hair, I’ve lost my figure, and losing the ability to have a child would have crushed me. But that didn’t end up being the case, and 9 pounds, 11 ounces later I have one,” said Johnson, 40, who was diagnosed at age 34 and also carries a dangerous genetic mutation associated with breast cancer known as BRCA2.

One of the most protective treatments to prevent breast cancer from coming back is called “endocrine therapy,” which involves taking certain medications to help prevent the recurrence of cancer cells that feed on hormones such as estrogen or progesterone. The recommended duration of endocrine therapy is 5 to 10 years.

The study that Johnson participated in, called the POSITIVE Trial, followed 518 women age 42 or younger who paused their endocrine therapy for approximately 2 years while trying to get pregnant. The study enrolled women with what is known as early-stage breast cancer (up to stage III), which hasn’t spread beyond the breast or nearby lymph nodes. The women completed at least 18 months of endocrine therapy before pausing to try to get pregnant.

Among those in the study, the breast cancer recurrence rate was 8.9% within an average follow-up period of about 3.5 years. That rate was similar to the 9% average recurrence rate within 3 years established by previous research. The new POSITIVE Trial results were presented in December at the San Antonio Breast Cancer Symposium.

“These data from the POSITIVE Trial apply to women with early-stage breast cancer which is hormone sensitive who want to have a pregnancy and who want to interrupt endocrine therapy in order to have a pregnancy,” says lead researcher Ann Partridge, MD, MPH, vice chair of medical oncology at Dana-Farber Cancer Institute. “It doesn’t appear that pregnancy … or taking an endocrine therapy break confer a worse prognosis.”

Is Pregnancy Less Likely After Breast Cancer? 

Most breast cancer cases occur in middle aged or older women, but 5% of women age 40 and younger are diagnosed with the disease annually. The new research results are important because young women are increasingly delaying childbearing until their 30s. Breast cancer risk increases with age, so more women are facing the disease prior to having children or completing their families.

“The other important thing to note is that as people get older, it’s harder to get pregnant,” Partridge says. 

So a woman may be diagnosed in her early 30s, spend a year getting active treatment such as a mastectomy, chemotherapy, and radiation, and then be advised to take 5 to 10 years of endocrine therapy, essentially taking up most of her remaining years of fertility.

In addition to examining the safety of pausing endocrine therapy, the POSITIVE Trial results offered an important new area of analysis that many breast cancer survivors fretted about: the likelihood of getting pregnant. 

Previous research shows that chemotherapy can negatively impact fertility, while endocrine therapy is considered safe — although women should not take it while seeking to get pregnant, says oncologist and  Matteo Lambertini, MD, PhD, of the University of Genova, Italy, who is an expert in pregnancy after breast cancer.

“Half of newly diagnosed women say they are concerned about fertility,” Lambertini says. 

Researchers said POSITIVE Trial participants got pregnant or gave birth at rates the same as or higher than the general population.

Among the 74% of participants who got pregnant, 86% had a live birth. Some women did spend longer than the recommended 2 years paused from endocrine therapy, according to data presented at the symposium. Among participants, 75% had no prior births, 94% had stage I or II breast cancer, and 62% received chemotherapy.

Partridge says 43% of women in the study used some form of assistive reproductive technology (ART), such as in vitro fertilization (IVF), but researchers haven’t yet analyzed what proportion of pregnancies were a result of ART.

“Sometimes people are using ART not because they are infertile, but because they want to avoid a BRCA mutation or they want to get pregnant faster using embryos,” Partridge says. “Especially for a BRCA mutation carrier, they may want to implant an embryo that has no mutation … We have to dive much deeper into those data. There’s lots of nuance.”

Partridge and Lambertini caution that longer follow-up among the study participants is needed to fully understand any longer-term risks pregnancy or pausing endocrine therapy may have.

Fertility to the Forefront 

Caitlin Baltera, 34, of Colorado Springs, CO, is 1 year in to her 2 years of paused endocrine therapy while trying to get pregnant. 

“It’s definitely hard being told that you have 2 years,” says Baltera, who was diagnosed with stage I breast cancer at age 30. “Of course, everyone tells you when you’re trying to conceive, ‘Be calm. Don’t worry.’ And I’m like, I only have 2 years.”

“Most people don’t usually have a cutoff point where if you continue to try you may be putting yourself in danger,” she says.

Baltera, who was starting a new relationship when she was diagnosed and is now married, has spent nearly $30,000 on fertility treatments, some of that toward pre-paid IVF cycles. She says her insurance did an excellent job of covering the costs of her cancer treatments, which included chemotherapy that is known to affect fertility.

Some breast cancer survivors are starting to call for changes in how fertility is covered, similar to a previous movement that surrounded coverage of breast reconstruction. U.S. law now requires that most group insurance plans cover the cost of breast reconstructive surgery.

“It has made me angry many times to think it’s covered if you want to have a reconstruction or whatever your option is, whether it’s fat grafting or implants, that’s all covered. But with fertility, it’s different,” Baltera says. “Many of us, we are medically infertile. And if you’re going to be proud of offering reconstruction, there’s this other side effect that seems to not be mentioned.”

Caragh Logan, of London, agrees that there needs to be more focus on the impacts of breast cancer on fertility. She was among the many women in a Babies After Breast Cancer Facebook group eagerly awaiting the POSITIVE Trial results.

“There are so many young women going through breast cancer every year having to make really hard decisions, and we need some direction, we need some clarity,” says Logan, who is 37. “If this were men, and the risk were men’s, I think they would have looked at things like this earlier.”

Logan was diagnosed with breast cancer in 2017 and had a recurrence that spread to her spine in 2020. But after treatment she has had what’s called no evidence of disease. She asked her oncologist if the POSITIVE Trial results would apply to her situation, since her cancer had advanced past the trial parameters but then responded to treatment.

“My previous oncologist said he’d be happy for me to try when I got to my 5 years on tamoxifen [a hormone therapy for breast cancer] in October 2023 if I were willing to accept the risk,” Logan says. “But he recently retired and the new oncologist is much more cautious.”

She had her eggs harvested prior to her first treatment and will consider surrogacy if she doesn’t move forward with trying to carry a pregnancy. But that’s something she says she will evaluate when her 5 years of endocrine therapy are complete.

Lambertini says breast cancer experts are planning next year to formally start discussing the matter of pregnancy for women with breast cancer that was more advanced than that studied in the POSITIVE Trial. Because treatments have become so successful, women are living longer than ever before with a stage IV (or metastatic) breast cancer diagnosis. One of Lambertini’s stage IV patients has had a complete response to treatment for 6 years and wants to have a child.

“Right now we cannot say it is safe at all because we don’t have any data,” he says. “We may potentially cure patients with advanced disease. She is 39. So she is still completely on time to have a pregnancy. But it’s a data-free zone. It’s very difficult for us, as well, to counsel our patients on this.”

Also forthcoming are results of a large international study looking at the safety of pregnancy among women who carry the BRCA genetic mutation, which is linked with increased cancer risks. Those results will be published in the fall of 2023, Lambertini says.