The Breast Cancer Detection Demonstration Project (BCDDP) was a nearly 20-year study of breast cancer screening. It collected information about patients' use of estrogen-only hormone replacement therapy and estrogen/progestin hormone replacement therapy, including age at first use and duration of use. Lacey and associates reviewed information from the BCDDP to determine whether there were increases in ovarian cancer in women receiving hormone replacement therapy.

Information was collected from participants, and during the follow-up phases, information about menopausal status, occurrence of gynecologic surgeries, and risk factors for ovarian cancer were recorded. Women who became menopausal or who were menopausal before the start of the follow-up were included. During the second phase, the lifetime history of ovarian cancer was determined; during phases 3 and 4, occurrence of ovarian cancer since the previous interview was determined.

There were 44,241 women included for analysis in the first follow-up interview. There were 329 women who developed ovarian cancer by the time of the final interview. Compared with women who had never used any hormone replacement therapy, women who had ever used estrogen replacement therapy (ERT) had a significantly higher rate of ovarian cancer (relative risk [RR], 1.6), even after adjusting for age, menopausal status, and use of oral contraceptives. Increasing duration of ERT use was significantly associated with increasing rates of ovarian cancer (RR of 3.2 in those who had used ERT for at least 20 years). Estrogen/progestin replacement therapy (EPRT) was not associated with increased rates of ovarian cancer, but the number of women in this group was very small.

The authors conclude that use of ERT was associated with development of ovarian cancer, with higher rates in women who used ERT longer. Further studies are needed to determine if EPRT also increases risk of ovarian cancer.