Dr. Susan Love Research Foundation | Breast Cancer

Women who have had breast cancer and still hope to bear a child will be interested to learn that a new research study found that pregnancy does not increase the risk of recurrence or death in women who have had an early stage breast cancer (Stages 0–II).

The study, "Effect of Pregnancy on Overall Survival After the Diagnosis of Early-Stage Breast Cancer," published in the March 15, 2001, Journal of Clinical Oncology, was conducted by researchers affiliated with the International Breast Cancer Study Group (IBCSG).

About 25 percent of women who are diagnosed with breast cancer are of childbearing age. Some have not yet had a first child; others had hoped to have more. But whether pregnancy post-treatment would increase the risk of recurrence hasn’t been clear.

Studies carried out during the 1990s indicated that pregnancy did not appear to decrease survival. But problems with the design of these studies—often there was no comparison group—led doctors to question these results and left women with little to go on. Clearly, more information was needed.

To fill this gap, IBCSG researchers conducted a retrospective review of women with breast cancer who had seen doctors affiliated with the IBCSG. The researchers first looked at the records of 94 women who had become pregnant after having been diagnosed with early stage breast cancer. They then matched each woman who became pregnant with two women who had not become pregnant but had been disease-free for the same length of time and had a similar nodal status, tumor size, age at diagnosis, and year of diagnosis. This matching process allowed the researchers to compare survival differences between the 94 women who became pregnant and the 188 who had not.

For the women who became pregnant, the 5-year survival rate was 92 percent and the 10-year survival rate was 86 percent. For the women who did not become pregnant, the 5-year survival rate was 85 percent and the 10-year survival rate was 74 percent.

Why pregnancy would increase survival, as this study found, isn’t clear. It’s possible that the women who chose to get pregnant had a better prognosis than the women who chose not to become pregnant did. It’s also possible that the changes that occur in a woman’s estrogen and progesterone levels during pregnancy were in some way protective against breast cancer. But we don’t yet know enough about breast cancer to explain why or how that might be.

As the percentages indicate, though, pregnancy could not keep cancer at bay. About one-third of the women who became pregnant had a cancer recurrence, eight during their pregnancy and 27 after they had given birth; 11 of these women died.

This is why although this new research provides the reassurance that becoming pregnant won’t increase the risk of recurrence it doesn’t—and can’t—erase the concerns a woman who has had breast cancer and is considering pregnancy will have. What happens to a group of women statistically isn’t what will happen to each individual woman. And this is why the decision to become pregnant after a breast cancer diagnosis will never be easy. Despite treatment, the cancer may have spread. And there is always a risk of recurrence.

This study does not address whether assisted pregnancy techniques—like in vitro fertilization—which require giving women hormones, would affect recurrence rates. We do know, though, that women who have had breast cancer have used these techniques and have had successful pregnancies.

For some women, the fact that a cancer can recur may lead them to choose not to become pregnant. For others, the knowledge that becoming pregnant won’t increase their risk of recurrence may tip the balance in favor of pursuing a pregnancy. The decision is still not easy. But now there is more information available to help every woman decide which decision is right for her.