February 6, 2018
For breast cancer survivors, the risk of giving birth prematurely, and of other health concerns for their newborns, may depend upon the type of breast cancer they had, according to a study led by Hazel B. Nichols, PhD, assistant professor of epidemiology at the UNC Gillings School of Global Public Health and member of the UNC Lineberger Comprehensive Cancer Center.
Published Jan. 4 in the International Journal of Cancer, the study analyzed health indicators for children born to young breast cancer survivors in North Carolina. This included evaluating whether newborns were born preterm (less than 37 weeks), were below normal weight or small for gestational age, or were born through a Cesarean delivery. Overall, there was no increase in the prevalence of preterm birth, C-section, small for gestational age, or low birth weight for newborns across all breast cancer types.
“We’re focusing on these outcomes because we know that child development in utero is important, and every week matters,” Nichols said.
However, when researchers examined the data by breast cancer type, they found increased risk of preterm birth, low birth weight, and C-section delivery for women with estrogen receptor-negative breast cancer. Researchers cautioned that further studies are needed to confirm the finding.
“The good news is that overall, women who conceived after their breast cancer diagnosis did not have an increased risk of preterm birth,” Nichols said. “However, when we looked more closely, we saw that women with estrogen receptor-positive breast cancer didn’t have an increased risk of preterm birth, but women with estrogen receptor-negative breast cancer did—and it was almost twice as high. What we need to do next is to see if this same finding is replicated in larger studies.”
As survival rates for breast cancer improve, more women face questions about their lives after cancer, including about their plans to start, or complete, their families. Studies from Canada and Europe have found there is a lower incidence of childbirth for breast cancer survivors compared to women of the same age in the general population. Previous studies have pointed to higher risks of low birth weight and preterm deliveries compared to women without breast cancer. However, these risks have not been examined by breast cancer type, the researchers said.
“This study is one piece of a larger effort to understand the needs of women with breast cancer beyond their cancer treatment,” Nichols said. “A breast cancer diagnosis can have an impact upon many different aspects of one’s life, and building a family is one of them. Increasingly, research is focused upon providing answers for women’s long-term questions.”
The study used N.C. Central Cancer Registry data to analyze the cases of 4,978 women diagnosed with breast cancer in North Carolina between 2000 and 2013. For the group overall, they found no significant difference in the prevalence of preterm birth, low birth weight, and other measures between women with or without breast cancer. Among women with estrogen receptor-negative breast cancer, however, 18 percent of births were preterm. That compares to a rate of about 10 percent of all births in North Carolina that are preterm.
Nichols cautioned that researchers need to ensure this is a real finding by examining a larger number of patients.
“Fewer women have estrogen receptor negative breast cancer, so our results were based on a small number of women,” Nichols said. “Now, we need to see whether the same pattern occurs in other studies as well.”
Analyzing the number of live births to women that occurred after their diagnosis, Nichols and colleagues found that about 8 percent of those women had had at least one child by 10 years after their diagnosis.
Compared to the general population, the birth rate for women with breast cancer in the study was about 57 percent lower than for women who did not have breast cancer, Nichols noted. Births were less common in women who received chemotherapy, and in women who had breast cancer at more advanced stages.
While researchers found that women with estrogen receptor-negative breast cancer were initially more likely to have children after their breast cancer diagnosis than were women with estrogen-receptor positive breast cancer, the proportion of women who went on to have children (about 10 percent) was similar in both groups 10 years after diagnosis.
Researchers say this difference could be attributed to treatment for estrogen receptor-positive breast cancer. It is recommended that these treatments, which target estrogen, be taken at least five years to prevent cancer recurrence. A clinical trial at UNC Lineberger and other centers is investigating whether endocrine therapy can be interrupted safely to allow women to conceive during this period.
“Though women who have estrogen receptor-positive breast cancer are less likely to have a child in the first five years following their diagnosis, they do catch up by 10 years,” Nichols said. “We’re seeing lower birth rates during the time period when they’re most likely to be taking endocrine therapy.”
The researchers also plan to survey young women with breast cancer later this year to probe possible explanations for the lower birth rate among breast cancer survivors. They hope to determine whether it is a side effect of treatment or the women chose not to become pregnant. They also intend in a future study to evaluate whether preterm birth affects later outcomes for the child’s health.
Nichols said that the study’s findings reinforced that fertility counseling is important for breast cancer patients who may want to have children.
“There are very consistent recommendations that women who are diagnosed with breast cancer should be counseled before they’re treated about any potential risks of their cancer treatment on future fertility,” Nichols said. “I think we need to do a better job making sure all women with cancer get the information they need before they start their treatment.”
In addition to Nichols, other authors from the UNC Gillings School include Chelsea Anderson, epidemiology doctoral student, and Stephanie M. Engel, PhD, associate professor of epidemiology. Also a co-author is Carey Anders, MD, UNC Lineberger member, medical director of the UNC Breast Center, and associate professor in the UNC School of Medicine’s Division of Hematology/Oncology.
The study was funded by the National Cancer Institute and the National Center for Advancing Translational Sciences.
A version of this article originally was posted on the UNC Lineberger website.