NEW YORK (Reuters Health), Mar 26 - 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 for April 2.
The findings stem from an analysis of follow-up data for 442 women with previously treated breast cancer who were enrolled in the Hormonal Replacement After Breast Cancer--Is it Safe (HABITS) study, a randomized trial that was stopped early after HRT use was linked to an increase in cancer events.
During a median follow-up of four years, 39 of 221 HRT-treated women had a breast cancer recurrence compared with 17 of 221 women in the control group, resulting in a hazard ratio of 2.4, lead author Dr. Lars Holmberg, from King's College London, and colleagues note. At five years, the corresponding cumulative rates of recurrence were 22.2% and 8.0%.
At latest follow-up, six breast cancer deaths and six surviving cases with metastatic disease were identified in the HRT group compared with five such deaths in the control group and four cases of metastatic disease, the report indicates.
"Further data from randomized studies are needed 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," the authors conclude.
In a related editorial, Dr. Kathleen I. Pritchard, from the Sunnybrook Odette Cancer Centre in Toronto, discusses the pitfalls of research from observational studies and comments that "in settings such as the HRT controversy ... randomized trials such as HABITS were long overdue."
She adds that "it is hoped that we can learn from this experience to move quickly to interventional studies with robust controlled designs in settings in which observational data clearly have the potential to mislead us."
J Natl Cancer Inst 2008;100:451-452,475-482.
Last Updated: 2008-03-25 16:00:26 -0400 (Reuters Health)
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