The first study to address head-on a major issue for young breast cancer survivors - the opportunity to have a baby - finds it's safe, at least temporarily, to pause treatment in order to get pregnant.
Until now, there had been no solid evidence that women who stopped taking hormone-reducing drugs so they could have a baby could do so without further increasing their risk of recurrence. The first-of-its-kind study was presented Thursday at the San Antonio Breast Cancer Symposium, an annual meeting of breast cancer specialists.
"Some young women just look at you and say, 'I'm not taking it. I want my baby,'" said Dr. Ann Partridge, vice chair of medical oncology at Dana-Farber Cancer Institute and professor of medicine at Harvard Medical School, who led the new research.
Less than 10% of breast cancers are diagnosed in women during their childbearing years, under age 45, according to the Centers for Disease Control and Prevention. Up to 60% of those women fear the drugs used to treat their cancer will impact their ability to have babies, Partridge said.
Side effects of endocrine therapy
Women with hormone-receptor positive tumors - meaning their cancer is fueled by either estrogen or progesterone - are usually advised to take endocrine therapy for up to 10 years after diagnosis to dampen down any hormones that could prompt a return of their cancer. Examples of endocrine therapy include aromatase inhibitors and ovarian suppression medications to lower estrogen levels, as well as drugs like tamoxifen to block estrogen from attaching to cancer cells.
The side effect of the drugs, however, is that they can destroy any chances of getting pregnant or having a healthy baby. Faced with this possibility, Partridge said, many women stop or never start endocrine therapy, against the advice of their doctors.
"For the women who are likely to be cured and don't want their future fertility taken away, how can we help them to both get the optimal breast cancer care and risk reduction, and at the same time complete their families?" said Partridge.
The new study included 518 women aged 42 or younger. All had been on endocrine therapy for at least a year-and-a-half before stopping treatment to try to get pregnant. Researchers encouraged the women to wait no more than two years to return to the therapy.
Within three years of stopping hormone-suppressing drugs, the rate of recurrence was 8.9% - similar to what would be expected in patients who stuck with the medications, Partridge said.
The findings were highly anticipated by other breast cancer specialists.
"This is definitely a big breakthrough," said Dr. Kai Johnson, a breast medical oncologist with the Ohio State University Comprehensive Cancer Center. "I think it's practice-changing, because we can confidently tell women" that a gap in their endocrine therapy doesn't seem to impact their risk of a recurrence.
Dr. Jennifer Litton, a breast medical oncologist at MD Anderson Cancer Center in Houston, agreed. Women in her practice were already making the executive decision to stop endocrine therapy for the chance of having a baby.
"A lot of women in America are making this decision right now," said Litton. "This data can be cautiously reassuring." Neither Johnson nor Litton were involved in the new research.
Many of the participants - 63% - were able to get pregnant and have a baby.
Shayla Johnson, 40, was one of those women.
Johnson was diagnosed with stage 2 breast cancer at age 34. Her doctor said that if her cancer were to spread, it would likely do so quickly. She opted for a double mastectomy followed by eight rounds of chemotherapy.
But the possibility that further treatment might destroy her chances of having a child was devastating.
"Without a doubt, the idea of not being a mother was worse to me than having cancer," she said. "I remember questioning my womanhood more so than when I lost my breasts."
She stopped her endocrine therapy, and got pregnant with baby Ronin, who turned 11 months this week. Her motherly pride is palpable.
"He has a big personality," Johnson said. "I make a face at him and he just cracks up. I could do it for an hour straight, and he'll just keep laughing."
More than three-quarters of the study participants have returned to their hormone-suppressing medications. The women will be monitored for 10 years for long-term effects of either pausing the therapies or pregnancy itself, which floods the body with hormones.
"The concern has been that the hormones themselves would increase the risk of the cancer coming back, that we would somehow wake up cells that were hiding," Partridge said. "We obviously need to follow them to make sure that it's safe over time."
"But so far, we have seen no increased risk," she said.
This article was originally published on NBCNews.com