Hormone replacement therapy (HRT) not only increases the risk of first-time breast cancer, it also makes recurrence of the malignancy more likely, according to a report in the Journal of the National Cancer Institute.

The findings stem from an analysis of follow-up data for 442 women who were previously treated for breast cancer and were enrolled in the Hormonal Replacement After Breast Cancer-Is it Safe (HABITS) study, a trial that was stopped early after HRT use was linked to an increased risk of cancer.

During a follow-up period of around 4 years, 39 of 221 HRT-treated women had a breast cancer recurrence compared with 17 of 221 women who did not take HRT. This suggests that HRT more than doubled the risk of repeat breast cancer, lead author Dr. Lars Holmberg, from King’s College London, and colleagues note.

At 5 years, 22 percent of HRT-treated women and 8 percent of the other women had a cancer recurrence.

At latest follow-up, six breast cancer deaths and six surviving women with metastatic cancer were identified in the HRT group compared with five deaths in the non-HRT group and four cases of metastatic disease, the report indicates.

The authors call for further studies “to define both the impact of specific types of HRT regimens and accompanying circumstances on the risk of recurrence in breast cancer survivors following HRT exposure.”

SOURCE: Journal of the National Cancer Institute, April 2, 2008.