ASCO 2017: Pregnancy After Breast Cancer Does Not Increase Chance of Recurrence
Findings from a retrospective study of 1,200 women provide reassurance to breast cancer survivors who are contemplating pregnancy. In the study, women who became pregnant after an early breast cancer diagnosis, including those with estrogen receptor–positive tumors, did not have a higher chance of cancer recurrence and death than those who did not become pregnant. The study was presented by Lambertini et al today at the 2017 ASCO Annual Meeting (Abstract LBA10066).
Breast cancer is the most common cancer in women of reproductive age. Taking into account current trends toward delaying childbearing, breast cancer in young women may occur before the completion of reproductive plans. Although half of young women with newly diagnosed breast cancer report interest in having children, less than 10% become pregnant after treatment, according to a study by Letourneau et al in Cancer. In fact, of all cancer survivors, breast cancer survivors are the least likely to have a baby after diagnosis.
Doctors and patients have long been concerned that pregnancy could increase the chance of breast cancer recurrence, particularly for women with estrogen receptor–positive disease. Because estrogen receptor–positive breast cancer is fueled by estrogen, the fear is that hormone levels during pregnancy could coax any occult cancer cells to grow.
Another concern regarding pregnancy in women with estrogen receptor–positive cancer is the need to interrupt adjuvant hormone therapy before trying to achieve a pregnancy. Such hormone therapy helps prevent cancer recurrence, and it is recommended that women receive it for at least 5 years—and in some cases, up to 10 years.
“Our findings confirm that pregnancy after breast cancer should not be discouraged, even for women with [estrogen receptor–]positive cancer,” said lead study author Matteo Lambertini, MD, a medical oncologist and European Society for Medical Oncology fellow at the Institut Jules Bordet in Brussels, Belgium. “However, when deciding how long to wait before becoming pregnant, patients and doctors should consider each woman’s personal risk for recurrence, particularly for women who need adjuvant hormone therapy.”
About the Study
With 1,207 patients, this is the largest study to investigate the safety of pregnancy after breast cancer and the only to address this question specifically in women with estrogen receptor–positive breast cancer, according to the authors.
This study included women younger than age 50 who were diagnosed with nonmetastatic breast cancer before 2008. The majority (57%) had estrogen receptor–positive cancer, and more than 40% had poor prognostic factors, such as large tumor size and cancer spread to the axillary lymph nodes. Among the 1,207 patients included in the study, 333 of the women became pregnant, and 874 did not (as per the case-control study design, researchers matched each patient who became pregnant with three patients who had similar cancer characteristics but did not become pregnant). The median time from diagnosis to conception was 2.4 years. Women with estrogen receptor–positive breast cancer tended to achieve pregnancy later than those with estrogen receptor–negative disease; 23% of patients with estrogen receptor–positive disease had a pregnancy beyond 5 years from diagnosis as compared with 7% in those with estrogen receptor–negative tumors.
Key Findings
After a median follow-up of about 10 years from cancer diagnosis, there was no difference in disease-free survival between women who became pregnant and those who did not, irrespective of estrogen receptor status. Secondary analyses showed there was no difference in disease-free survival compared with women who did not become pregnant, irrespective 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. Among survivors of estrogen receptor–positive cancer, there was also no difference in overall survival between women who became pregnant and those who did not. Survivors of estrogen receptor–negative breast cancer who became pregnant had a 42% lower chance of dying than those who did not become pregnant.
“It’s possible that pregnancy could be a protective factor for patients with estrogen receptor–negative breast cancer, through either immune system mechanisms or hormonal mechanisms, but we need more research into this,” said Dr. Lambertini.
Although there were limited data on breastfeeding in this study (64 patients, with 25 women who reported having breastfed their newborn), the results suggest that breastfeeding is feasible, even after breast surgery.
Commentary
“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. For many young women around the world who want to grow and expand their families, it’s very comforting news,” said Erica L. Mayer, MD, MPH, an ASCO expert.
This study was partly supported by grants from Les Amis de l’Institut Bordet and the European School of Oncology. The International Breast Cancer Study Group study, which provided patient information for this study, was partially funded by the National Institutes of Health.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
