Study Proves Pregnancy Still a Safe Option After Breast Cancer Diagnosis

Women who conceive after an early breast cancer diagnosis do not have an increased risk of disease recurrence and death compared with patients who did not become pregnant, a recent study found. This includes women with estrogen receptor (ER)-positive tumors.

The findings, presented at the 2017 American Society of Clinical Oncology annual conference in Chicago, helps reassure breast cancer survivors who are grappling with pregnancy, according to the authors.

There have been ongoing concerns about whether pregnancy could increase the chance of breast cancer recurrence, especially for women with ER-positive tumors. This is largely because ER-positive breast cancer is fueled by estrogen, and physicians fear that a rise in hormones during pregnancy could stimulate leftover cancer cells to grow.

Another concern is that adjuvant hormone therapy needs to be interrupted before trying to conceive, according to the study. The therapy helps prevent cancer recurrence, and women are recommended to continue adjuvant hormone treatment for at least 5 years.

“Our findings confirm that pregnancy after breast cancer should not be discouraged, even for women with ER-positive cancer,” said lead author Matteo Lambertini, MD. “However, when deciding how long to wait before becoming pregnant, patients should consider each woman’s personal risk for recurrence, particularly for women who need adjuvant hormone therapy.”

Included in the study were 1207 women under 50 years of age diagnosed with non-metastatic breast cancer before 2008. Most of the participants had ER-positive cancer, and more than 40% had poor prognostic factors, such as large tumors and metastasis to the axillary lymph nodes.

Among the 1207 women, 33 became pregnant and 874 did not. The median time from diagnosis to conception was 2.4 years.

Women with ER-positive breast cancer tended to become pregnant later than those with ER-negative disease. Of the participants with ER-positive disease, 23% had a pregnancy beyond 5 years from diagnosis compared with 7% in patients with ER-negative tumors.

The results of study showed that there was no difference in disease-free survival after a median follow-up of approximately 10 years from cancer diagnosis between women who became pregnant and those who did not, regardless of ER status.

The secondary analyses showed that there was no difference in disease-free survival compared with women who did not become pregnant, regardless of whether women completed the pregnancy or had an abortion, became pregnant less than 2 years or more than 2 years from breast cancer diagnosis, and whether patients had breastfed.

There was no difference in overall survival among ER-positive breast cancer survivors who had become pregnant and those who had not. ER-negative cancer survivors who became pregnant had a 42% lower chance of dying compared with those who did not become pregnant.

“It’s possible that pregnancy could be a protective factor for patients with ER-negative breast cancer, through either immune system mechanisms or hormonal mechanisms, but we need more research into this,” Dr Lambertini.

The authors noted that there were limited data regarding breastfeeding, but that findings suggest that breastfeeding is feasible even after surgery.

Limitations to the study were the lack of data on the use of assisted reproductive technologies in breast cancer survivors, as well as HER2 status being unknown in approximately 80% of women. More research needs to be done to study the effect of pregnancy on the health outcomes of women with BRCA mutations. Currently, the large POSITIVE clinical trial is underway to examine the impact of interrupting adjuvant hormone therapy to allow for women with ER-positive breast cancer to conceive. Furthermore, the study will provide additional insight on the impact of breastfeeding and reproductive surgeries, such as in vitro fertilization, according to the authors.

“These data provide reassurance to breast cancer survivors that having a baby after a breast cancer diagnosis may not increase the chance of their cancer coming back,” said Erica L. Mayer, MD, MPH, ASCO expert. “For many young women around the world who want to grow and expand their families, it’s very comforting news.”