Contrary to past belief, it is safe to become pregnant after being treated for breast cancer, according to new research presented today at the eighth European Breast Cancer Conference in Vienna, Austria.
The research was specific to women who were diagnosed with estrogen-receptor positive tumors, which have protein molecules that need estrogen to grow. About 60 percent of all breast cancers are ER-positive, according to the National Institutes of Health.
Despite the fear that high hormone levels that occur during pregnancy might stimulate breast cancer growth, data overwhelming showed that it does not, experts said.
The study included 333 women ages 21 to 48 who became pregnant after a breast cancer diagnosis and 874 women with similar breast cancer diagnoses who did not become pregnant. About five years after pregnancy, researchers found about 30 percent of all the women had a recurrence of the cancer.
In the past, some women who became pregnant were advised to get abortions because of the potential dangers of recurrence, but researchers said this recommendation might be unnecessary in most cases.
The study showed that there was no difference in recurrence among women who became pregnant and those who did not. Indeed, women who became pregnant within two years of their breast cancer diagnoses might have better "disease-free survival" than those who did not become pregnant at all. But researchers warned that this observational finding must be more rigorously researched before presenting it as fact.
"These … messages are vital as women with ER+ disease were frequently advised against pregnancy for fear that pregnancy could stimulate the recurrence of the disease by means of hormonal stimulation," Dr. Hatem Azim, lead author of the study and medical oncologist at the Jules Bordet Institute in Brussels, wrote in an email.
This is the first study ever to address the impact of pregnancy on breast cancer outcome in patients with this kind of breast cancer, Azim said. It is also the first study to provide reliable information on the role of abortion and insights on the time to become pregnant after a breast cancer diagnosis.
"The literature is overall very reassuring that women who become pregnant after having breast cancer are not adversely affecting their cancer health outcomes," said Dr. Kathy Helzlsouer, director of the Prevention and Research Center at Mercy Medical Center in Baltimore. "This study reported in abstract form is notable for its large sample size. Studies to date have been small and few have been able to study the impact according to the type of tumor."
Dr. Wright Bates, director of the division of reproductive endocrinology and infertility at University of Alabama at Birmingham, said the results give an oncologist more reassurance that we can tell patients they can safely pursue pregnancy without worrying about the recurrence of cancer.
Lead author Azim agreed, and, in addition, "it will hopefully reduce the percentage of women subjected [to] abortion, on the basis that this could improve their outcome, which is actually not true," he said.
"And hopefully," Bates said, "this paper will increase the number of women who are referred to a discussion on the future of fertility and allow for effective counsel on their options."