Pregnancy safe after treatment for early-stage breast cancer

Pregnancy after early-stage breast cancer is safe and does not cause breast cancer to return, according to findings from an international study.

That heartening news — for women diagnosed with estrogen receptor-positive or estrogen receptor-negative breast cancer — came from long-term results presented at the American Society of Clinical Oncology (ASCO) 2017 annual meeting.

Background

For young women, a breast cancer diagnosis may interrupt plans to have children in the future because some cancer treatments can impact a woman’s fertility. Often, women put off having children to complete cancer treatment because many treatments can harm a fetus.

Many young women express interest in having children after they finish breast cancer treatment, but only about 10 percent do. For decades, doctors and other care providers told women they should not get pregnant after having breast cancer. A chief reason for this was the belief that levels of estrogen, a hormone known to cause some breast cancer types to grow, increase during pregnancy.

Doctors worried that the added estrogen during pregnancy might feed cancer cells left behind after breast cancer treatment and cause the breast cancer to grow again, especially in estrogen receptor-positive disease.

The researchers on this study wanted to find out if pregnancy causes breast cancer to return or raises the risk of death from the disease. Their primary aim was to study how long women with estrogen receptor-positive breast cancer lived after pregnancy without the cancer returning, called disease-free survival. They also looked at this in women with ER-negative breast cancer, and at overall survival, the risk of death from any cause, in all participants.

An important concern for women with estrogen receptor-positive disease is that hormonal therapy, which is taken for up to 10 years after primary cancer treatment, can harm a fetus. These medicines should be stopped before a woman tries to become pregnant to protect the health of the fetus.

Design

This study was conducted in Europe and Boston. It looked back at records of 1,207 women who were diagnosed with early-stage breast cancer before 2008.

All women studied were younger than 50 at diagnosis. A little over half of them had estrogen receptor-positive disease, and about 40 percent had large tumors or breast cancer that had spread to their lymph nodes, putting them at higher risk of the cancer returning.

The researchers compared each woman who became pregnant after treatment ended with three peers who did not become pregnant but who had similar stages and types of breast cancer. To be matched, each woman who did not get pregnant had to have been living without cancer returning for the amount of time that passed between diagnosis and her peer becoming pregnant.

This is the largest study to date looking at pregnancy’s effects on breast cancer. Earlier results from the same group of women had reported findings over 5 years from diagnosis. This study updates those findings with data on participants’ health for at least 10 years following breast cancer diagnosis.

Results

The results showed no difference in disease-free survival between the women who became pregnant and those who did not. This was true for all of the women, whether they had ER-positive or ER-negative disease.

In estrogen receptor-positive women, there was no difference in overall survival between those who became pregnant and those who did not.

Women with estrogen receptor-negative breast cancer who became pregnant showed a 42 percent lower risk of death from any cause than did those who did not become pregnant.

Limitations

The results have only been presented in an abstract. The full study and its findings have not yet been published.

The participants were diagnosed 10 or more years ago, so their active treatments — chemotherapy, radiation therapy, and surgery — may have been different than those used today. Also, women who try for a pregnancy often are healthier than those who don’t, and that might affect the findings.

What this means for you

After seeing these findings, you may feel better about becoming pregnant after early-stage breast cancer, even if you were diagnosed with ER-positive disease. Knowing that pregnancy does not seem to impact survival can relieve a lot of stress you may be feeling.

Breast cancer can return in anyone, including in women who become pregnant, either during or after the pregnancy. But those recurrences do not appear to be more frequent in women who have pregnancies after treatment compared to women who don’t become pregnant.

If you have already completed hormonal therapy, pregnancy will not affect your outcome, says Kathryn J. Ruddy, MD, MPH, an oncologist and director of cancer survivorship at the Mayo Clinic in Rochester, Minnesota.

But if you are on hormonal therapy, will taking a break to have a child increase your risk? That decision depends on your personal risk of recurrence, said the study’s lead author, Matteo Lambertini, MD, to an audience at ASCO. The findings in this study are likely to bring more interest to studying the effects of stopping hormonal therapy early to become pregnant.

A large clinical trial, called the POSITIVE study, is looking at whether women can safely stop hormonal therapy for a short time, to attempt pregnancy and deliver a baby. The trial is no longer enrolling participants. You can access updates on this trial from the above link.

According to Dr. Ruddy, women “with the highest risk of recurrence” need to consider that if the cancer returned during pregnancy, it’s more difficult to treat. That’s because medicines for estrogen receptor-positive or HER2-positive disease are not safe to use when pregnant.

You may have heard in news reports that this study showed pregnancy can even help protect you from breast cancer coming back. So far, the study results do not show that pregnancy helps prevent recurrence. The lead researchers on the trial say pregnancy could be protective for those with estrogen receptor-negative disease, but more research is needed.

Talk with your oncologist about your interest in having children, your recurrence risk, and whether you can safely stop hormonal therapy. Right now, there’s no definitive answer about how long women with estrogen receptor-positive breast cancer should remain on hormonal therapy before taking a break to become pregnant.

 

Lambertini, M, Kroman, N, Ameye, L, et al. Safety of Pregnancy in Patients with History of Estrogen Receptor Positive (ER+) Breast Cancer: Long-Term Follow-Up Analysis from a Multicenter Study. Journal of Clinical Oncology, 2017; 35 (suppl; abstract LBA10066)

This article was supported by the Grant or Cooperative Agreement Number 1 U58 DP005403, funded by the Centers for Disease Control and Prevention. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the Centers for Disease Control and Prevention or the Department of Health and Human Services.