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Pregnancy After Breast Cancer Treatment Does Not Trigger Cancer Recurrence

Pregnancy After Breast Cancer Treatment Does Not Trigger Cancer Recurrence
M. D. Anderson News Release, 01/23/04

Women with a history of breast cancer need not worry that becoming pregnant will spark recurrence of the disease, say researchers at The University of Texas M. D. Anderson Cancer Center.

If anything, pregnancy appears to offer a slight protective effect against new breast cancer development, note the investigators, whose study will appear in the February 2004 issue of the journal Cancer (published online December 15, 2003).

Because breast cancer is, for the most part, hormone dependent and pregnancy is a condition in which hormone levels in women are at their highest, physicians have long advised patients not to become pregnant for several years following treatment, says study co-author, Aman Buzdar, M.D., professor in the department of Breast Medical Oncology.

“But from these findings, and that of other smaller studies, we can now say that pregnancy is not associated with an increased risk of disease recurrence or poorer survival in patients previously treated for breast cancer,” he says.

“This is welcome news,” says Buzdar. “There is no reason to discourage women who have been treated for breast cancer from bearing children.”

Treatment with chemotherapy results in loss of ovarian function for about 50% of women, most of whom are older, but younger patients often retain their ability to become pregnant. Few studies, however, have specifically examined whether pregnancy had a deleterious effect on breast cancer outcome, the researchers say.

To find the answer, Buzdar and his colleagues culled the records of 370 women treated for breast cancer at M. D. Anderson Cancer Center between 1974 and 1998, and who were followed by researchers for an average of 13 years. In this group, 47 patients (13%) had at least one pregnancy and within this group, 32 (9%) had full-term pregnancies.

The researchers looked at survival and disease recurrence between the groups and found that patients who had subsequent pregnancy were not at an increased risk of recurrence. In fact, they note that the risk of recurrence was somewhat lower in patients who became pregnant compared to those who had no subsequent pregnancy. One reason may be that patients who had a pregnancy tended to be younger and have an earlier stage breast cancer. But Buzdar adds that high levels of the female hormones produced during pregnancy also may have conferred a protective effect against disease recurrence.

Either increasing or decreasing the level of estrogen in a breast cell can help control cancer growth, says Buzdar. Before the advent of Tamoxifen as a treatment to treat breast cancer, large pharmacological doses of the hormone were considered a standard treatment for patients with the disease, he says.

“We know some of these tumors that are hormone dependent can be managed by large doses of estrogen,” says Buzdar. “During pregnancy, the body is producing an extensive amount of hormones which may have a beneficial effect on any cancer cells if still remaining behind, and may be able to eliminate them.”

The study was funded by M. D. Anderson Cancer Center and all authors of the study were from the cancer center. They include L. Johnetta Blakely, M.D., Jose Lozada, M.D., Samer Shullaih, M.D., Emma Hoy, Terry Smith, and Gabriel Hortobagyi, M.D.

© 2015 The University of Texas MD Anderson Cancer Center