Hormone replacement therapy (HRT) increases the risk of disease recurrence in breast cancer survivors, warns a new study.
Previous studies have shown that HRT increases breast cancer incidence in peri- and postmenopausal healthy women, but its impact on breast cancer survivors has remained obscure.
Now, the study by Lars Holmberg, M.D., Ph.D., currently at King's College London and his mostly Scandinavian colleagues, has warned that survivors who took HRT were more likely to suffer disease recurrence than those who did not take HRT.
As a part of their study the researchers analysed breast cancer rates for 221 women in the randomized HABITS (Hormonal Replacement After Breast Cancer -Is It Safe?) trial after a median follow-up of four years.
At the time of this analysis, the researchers found that 17.6 percent or 39 women in the HRT treatment arm had developed breast cancer recurrence or a new breast cancer malignancy, compared with 7.7 percent or 17 women in the control arm.
The estimated 5-year cumulative rate for disease recurrence was 22.2 percent for the HRT arm and 9.5 percent in the control arm, for an absolute increase in risk of 14.2 percent.
"The results of the HABITS trial indicate a substantial risk for a new breast cancer event among breast cancer survivors using [HRT]. The risk elevation is in line with the evidence from observational studies and randomized trials that [HRT] increases the risk of breast cancer in healthy women," the authors write.
The findings were published online March 25 in the Journal of the National Cancer Institute.