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Combined Hormone Replacement Therapy May Increase Risk of Ovarian Cancer

Postmenopausal women who take continuously oestrogen plus progestin therapy may have an increased risk of ovarian cancer, but show rates of endometrial cancer similar to postmenopausal women not taking hormone replacement therapy, say researchers.

"Women taking oestrogen plus progestin were diagnosed as having invasive ovarian cancer at a rate of 42 per 100,000 person-years," reports Garnet L. Anderson, PhD, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States, "15 per 100,000 person-years more than the placebo group rate." Dr. Anderson and colleagues analysed the trial data, collected for the Women's Health Initiative (WHI) trial, from 16,608 postmenopausal women who had not had a hysterectomy at enrolment and were taking either 0.625 mg conjugated equine estrogens plus 2.5 mg medroxyprogesterone acetate or placebo to determine any possible associations between combined hormone replacement therapy and gynaecologic cancers and diagnostic procedures.

After 5.6 years of follow up, the researchers report a hazard ratio of 1.58 for invasive ovarian cancer among 8506 women assigned to oestrogen plus progestin compared with the 8102 women taking placebo. The hazard ratio was 0.81 for endometrial cancer among women taking the combined therapy compared with placebo.

The investigators report that uterine bleeding led to a higher frequency of biopsies and ultrasounds in the women taking combined hormones. Among women receiving usual care, "the fraction of women taking combined hormones and requiring diagnostic biopsies increased more than 5-fold over placebo (33% versus 6%; P<.001) and twice as many women required multiple biopsies (38% versus 17%; P.001)," the authors write. Likewise, transvaginal uterine ultrasound examinations were required in 12.8% of women taking combined therapy compared with 4.1% of those taking placebo. In follow up Papanicolaou test results available for 94% of the trial participants, 7.8% of the combined therapy group compared with 5.5% of the placebo group had mild dysplasia, low grade squamous intraepithelial lesions, or atypia. Normal Papanicolaou test results were found in 92% of the combined therapy group compared with 94% of the placebo group.

The authors conclude, "these data provide additional support for caution in the use of continuous combined hormones," noting "the possibility of an increased risk of ovarian cancer incidence and mortality remains worrisome." The WHI investigators add, "the increased need for diagnostic procedures in response to bleeding is an added burden and could reasonably affect a women's decision to use these medicines."

JAMA 2003;290:13:1729-1738. "Effects of Estrogen Plus Progestin on Gynecologic Cancers and Associated Diagnostic Procedures: The Women's Health Initiative Randomized Trial"

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