According to an extensive meta-analysis from the Collaborative Group on Epidemiological Studies of Ovarian Cancer, hormone replacement therapy (HRT) was associated with an increased risk for ovarian cancer in postmenopausal women.
To date, studies that have examined a link between HRT and ovarian cancer risk have been small and/or retrospective and many have remained unpublished. That is why the authors of this current study analysed several published and unpublished data collected since 1998. Their findings have been published in the Lancet.
The analysis included 21,488 women from 17 prospective and 35 retrospective studies. The case participant-patients were postmenopausal women with ovarian cancer and the control patient-participants were postmenopausal women without cancer who still had their ovaries.
They found that women who use HRT, even if it’s for a short duration of time, were 20 percent more likely to develop ovarian cancer as compared to women who have never used HRT. The more recent the therapy, the greater the risk. Women who were no longer taking HRT but were within five years of last use had a 23 percent increased relative risk. The longer the time since last use of HRT, the lower the cancer risk. Women who had used HRT for at least five years were still associated with a 10 percent increased relative risk more than five years later.
The researchers found that the risk of ovarian cancer was greatest in current users of hormone therapy and decreases after the use of this therapy ceases. The researchers project that if the relationship is causal, one additional ovarian cancer will occur for every 1000 users among women who take HRT for 5 years, starting near age 50. One extra ovarian cancer death will happen for every 1700 users.
Approximately 6 million women take HRT in the US and UK. None of the HRT Guidelines from the WHO, EU and US cite a link to elevated risk for ovarian cancer. UK guidelines state that the risk of ovarian cancer may increase with long-term use.
Risk of ovarian cancer is high for both oestrogen-only HRT and oestrogen-progestogen combinations. Other factors such as alcohol use, smoking, body size, and oral contraceptive use, age of HRT start, hysterectomy and family history were not found to be associated with increased risk.
These findings thus support the addition of ovarian cancer to the list of adverse effects associated with hormone replacement therapy.
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