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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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