Even short-term hormone replacement therapy use associated with increased ovarian cancer risk

the Oncology Nurse Advisor take:

A meta-analysis of 52 epidemiological studies on hormone replacement therapy (HRT) and ovarian cancer indicate that HRT use, even for less than 5 years, increased women’s risks of developing ovarian cancer. The reviewed studies represent virtually all the epidemiological evidence ever collected on HRT use and ovarian cancer.

The international Collaborative Group on Epidemiological Studies of Ovarian Cancer, involving more than 100 researchers worldwide organized by the University of Oxford, in the United Kingdom, analyzed individual participant data from 21,488 women with ovarian cancer, almost all from North America, Europe, and Australia. 

Their findings indicate that women who use HRT for just a few years have an approximately 40% higher risk of developing ovarian cancer than women who have never taken HRT.

This increase in risk was seen in only the two most common types (serious and endometrioid ovarian cancers), and not in mucinous and clear cell ovarian cancers, which are less common types. Study co-author Professor Dame Valerie Beral, from the University of Oxford, suggests that the definite increase in risk of ovarian cancer has implications for the current efforts to revise guidelines for HRT use.