July 15, 2009 — New results suggest that hormone therapy increases the risk for ovarian cancer. The findings held true regardless of the duration of use, dose, formulation, or route of administration, according to a study published in the July 15 issue of JAMA.
However, the risk declines quickly once the therapy is discontinued, said first author Lina S. Mørch, MSc, from the Gynaecological Clinic, Rigshospitalet, Copenhagen, Denmark.
"For women having concerns about their risk because they are on hormone therapy or have been taking hormones, our data suggest their risk of ovarian cancer is similar to never users after 2 years' cessation," said Ms. Mørch. "That is, women currently taking hormones seem to reduce their risk of ovarian cancer by quitting hormone use."
In a nationwide prospective cohort study, Danish researchers found that women who have taken hormone therapy are at higher risk for epithelial ovarian cancer (range, 30% to 58%) than those who have not used them.
Ovarian cancer is still a rare disease, Ms. Mørch told Medscape Oncology. "So despite a 40% increased risk of ovarian cancer among current hormone-therapy users, each woman will still have a very low absolute risk of developing cancer [because of] her hormone use."
Indeed, the absolute risk increase was 0.12 per 1000 years, and if the association was causal, then hormone use resulted in approximately an extra 140 cases of ovarian cancer in Denmark over a mean follow-up time of 8 years. This averaged out to about 5% of the ovarian cancers in this study. But even though this number seems low, the authors note, ovarian cancer remains a highly lethal disease, so this risk should be considered when deciding whether or not to use hormone therapy.
Higher Risk Even With Short-Term Use
Their data show an increased risk for ovarian cancer even with short durations of hormone use (from 0 to 4 years), but this result differed from findings of previous studies that were unable to identify an increased risk when hormone therapy was used for less than 5 years.
"Our short-term users included women with a few months' use and women with more than 3 years' use," said Ms. Mørch. "Some previous studies defined short-term use as use less than 1 year or so. These differences in categories may explain some of the difference between this and previous studies."
"In addition, some previous studies did not distinguish sharply between current and previous use," she added. "Women who were current users at the start of a study were often classified as current users, even though they had become previous users during the follow-up period. In our study, the duration analyses were conducted only among women currently taking hormones."
As previously reported by Medscape Oncology, studies have suggested that there is an increased risk for ovarian cancer among women taking postmenopausal hormone therapy. However, data are limited as far as the differential effects of formulations, regimens, and routes of administration.
Risk Declines Over Time With Therapy Cessation
In the current trial, Ms. Mørch and colleagues evaluated the risk for ovarian cancer in perimenopausal and postmenopausal women receiving a variety of hormone therapies using data from the Danish Sex Hormone Register Study, which identified all Danish women 50 to 79 years who used hormone therapy from 1995 to 2005. Overall, the cohort was comprised of 909,946 women without hormone-sensitive cancer or bilateral oophorectomy. Prescription data were obtained from the National Register of Medicinal Product Statistics, and the National Cancer Register and Pathology Register provided ovarian cancer incidence data.
After an average follow-up of 8 years, 3068 incident ovarian cancers, of which 2681 were epithelial cancers, were detected. Compared with women who had never used hormone therapy, current users had incidence rate ratios for all ovarian cancers of 1.38 (95% confidence interval [CI], 1.26 - 1.51) and for epithelial ovarian cancer of 1.44 (95% CI, 1.30 - 1.58). The risk declined as the number of years since hormone therapy was last used increased.
Risk After Discontinuation of Hormone Therapy
| Number of Years Since Last Use | Relative Risk (95% Cl) |
| 0 - 2 | 1.22 |
| More than 2 - 4 | 0.98 |
| More than 4 - 6 | 0.72 |
| More than 6 | 0.63 |
The incidence rate was 0.52 in current hormone therapy users and 0.40 in never users. Ovarian cancer risk did not differ significantly with duration of use among current users, and risk did not differ according to the dose, route of administration, or type of therapy. Compared with women who had never used hormone therapy, the risk for estrogen-only therapies was 1.31 (95% CI, 1.11 - 1.54), and the risk for combined estrogen-plus-progestin therapy was 1.50 (95% CI 1.34-1.68). The difference between them was not statistically significant.
The authors do not recommend screening for ovarian cancer at this time on the basis of hormone therapy use. "Unfortunately, we have no reliable or effective screening technique for ovarian cancer," said Ms. Mørch. "Even the combination of CA125 and ultrasound examination gives many false-positive cases, with unnecessary surgery as a consequence."
This study was supported by the Danish Cancer Society. Coauthor Øjvind Lidegaard, MD, DrMSci, from the Gynaecological Clinic, Rigshospitalet in Copenhagen, Denmark, reports receiving a grant from Schering AG to cover research expenses, and has received fees for speeches from Schering Denmark and Novo Nordisk. None of the other coauthors have disclosed any relevant financial relationships.
JAMA. 2009;302:298-305.
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