The latest report is an analysis of data collected from the Women’s Health Initiative (WHI) estrogen-alone clinical trail.  Although the study was cut short in March 2004, analyses of the preliminary data continue and participants follow-up with tests to monitor their health. The study included 10,739 generally healthy women, aged 50-79 years old without a uterus. The participants were randomly assigned to take a pill of either an estrogen treatment (0.625mg/day) or a placebo.

The women who were treated with the estrogen were 32% more likely to develop blood clots than those taking a placebo, according to the report. One hundred and eleven women treated with estrogen developed blood clots compared to 86 women taking placebos in a 7-year trial.

The blood clots commonly affected deep veins (a condition known as deep venous thrombosis or DVT).  These clots are typically in large veins like those found in the legs and can sometimes travel to the lungs.  Symptoms for DVT include the onset of pain and swelling in the legs with redness.

Blood clots in the lungs (pulmonary embolism) were also observed in the trials.  Symptoms of this type of blood clot may include rapid heartbeat, chest pain and difficult or painful breathing.

Breast Cancer and Estrogen

Two days later, there was good news released. According to the April 12, 2006 issue of the Journal of the American Medical Association (JAMA), estrogen-alone therapy is not associated with an increased risk of breast cancer as many researchers once suspected.

Previous Women’s Health Initiative (WHI) data (July 17, 2002) from estrogen-progestin trials shows an increased number of blood clots, breast cancer, heart attack and stroke in women with a uterus. As a result, the WHI trials were halted and many women stopped taking the combined therapy.

WHI’s estrogen-alone studies continued until March 2004.  At this time, data showed an increased risk of stroke and trials were halted.  However, the preliminary study revealed fewer occurrences of breast cancers in women who were taking estrogen-alone compared to a placebo.   With the need for additional studies, WHI extended their trials of estrogen-alone. Hence, the recent acquisition of results from JAMA.

“Some previous studies have associated estrogen with increased breast cancer incidence, and when the estrogen-plus-progestin arm of the WHI was halted, many suspected that it was the estrogen that led to the increased breast cancer risk.  These new findings appear to show otherwise,” says Dr. Isaac Schiff of the American College of Obstetricians and Gynecologists (ACOG) in an ACOG press release.

Implications of Recent Estrogen-Alone Data

The extension of the estrogen-alone studies increases our understanding of its effects on women.  We are now able to see if there is a connection between estrogen-alone and certain side effects or if they are a result of the combined estrogen-progestin therapy.

As new information becomes available to the public from the WHI estrogen-alone trials, women should be cautious about starting and/or continuing treatment.  Women definitely need to know the symptoms of DVT and pulmonary embolism.

As with any treatment, women taking hormone therapy should always discuss their previous medical history with their doctors.  Implications from these most recent WHI studies indicate women should only use estrogen-alone after careful consideration of risks and benefits.