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Another Hormone Replacement Therapy Study Stopped Due to Breast Cancer Recurrence Concerns (dateline February 11, 2004)

Another study on hormone replacement therapy (HRT) was halted, this time due to concerns that the hormones increase the risk of breast cancer recurrences in women with a history of the disease. In the study, conducted in Sweden, researchers were studying the effects of HRT in women who had been previously treated for breast cancer. However, after over three times as many women who were given HRT in the study developed breast cancer recurrences, compared to women who were not given HRT, the researchers decided to stop the study due to safety concerns. This is the latest HRT study to be halted prematurely based on the worry that HRT increases breast cancer risk.

In August 2003, researchers announced that results from the Million Women Study, a United Kingdom research project investigating reproductive and lifestyle factors affecting women’s health, showed that women who use or have used HRT are more likely to develop breast cancer, compared to women who have never used HRT.

In July 2002, a large clinical trial designed to learn the true benefits and risks of HRT was stopped early after U.S. government health officials found that study participants on one type of HRT were more significantly more likely to develop invasive breast cancer and other health problems compared to women who did not take the hormones. The HRT arm of the Women’s Health Initiative was supposed to settle the debate on HRT. Over 16,000 women with intact uteruses had been recruited to study whether estrogen plus progestin helped prevent heart disease and hip fractures, and whether the therapy caused any increased risks in breast cancer or colon cancer. The trial, run by the National Heart, Lung, and Blood Institute, was scheduled to continue to 2005. However, surprisingly negative results caused researchers to stop the study early, with participants being followed for an average of 5.2 years.

The findings that led to the halt of the combined estrogen/progestin arm of the Women’s Health Initiative consisted of an increased risk of invasive breast cancer and increased risks of coronary artery disease, stroke, and pulmonary embolism (blood clots in the lungs). Specifically, the study showed that during one year among 10,000 post-menopausal women with a uterus who took estrogen plus progestin, 8 more would have developed invasive breast cancer, 7 more would have had a heart attack, 8 more would have had a stroke, and 18 more would have developed blood clots, including 8 with blood clots in the lungs, compared with a similar group of 10,000 women who were not taking HRT. The study did find benefits to HRT, including fewer hip fractures (often a sign of osteoporosis) and a decreased risk of colon cancer.

The latest HRT study to be halted due to breast cancer concerns is the Swedish study called HABITS (Hormonal Replacement Therapy after Breast Cancer--Is it Safe?). In this study, women with a history of breast cancer were either given HRT or not given HRT, to determine whether HRT increased the risk of breast cancer in those with a prior history of the disease. After an average follow-up of 2.1 years, 26 women in the HRT group and only seven in the non-HRT group developed a recurrence of breast cancer.

"We decided that these findings indicated an unacceptable risk for women exposed to HRT in the HABITS trial, and the trial was terminated on Dec 17, 2003," wrote Dr. Lars Holmberg, of the Regional Oncologic Centre of University Hospital in Uppsala, Sweden and colleagues in the February 7, 2004 issue of The Lancet.

This announcement has prompted the American Cancer Society (ACS) to state that women with a history of breast cancer should avoid HRT. "In the past, some doctors have offered HRT to selected breast cancer survivors because a handful of small, preliminary studies had failed to show a risk," said Harmon J. Eyre, M.D., Chief Medical Officer of the American Cancer Society, in an online ACS report. "This study will no doubt change that. It is large enough and clear enough to show that… offering HRT to women with a history of breast cancer would be unwise."

It is important to note, however, that despite these new study results, HRT may still be appropriate for some women without a history of breast cancer. HRT is the most effective method of treating menopausal symptoms such as hot flashes and night sweats. Women who suffer from severe menopausal symptoms and have a low personal risk of breast cancer may wish to consider/continue HRT for a short duration. A thorough discussion of these issues with a physician is recommended for all women considering or currently taking HRT.

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