A new study has found that among women who have never used menopausal hormone therapy, obese women are at an increased risk of developing ovarian cancer compared with women of normal weight. The research indicates that obesity may contribute to the development of ovarian cancer through a hormonal mechanism.

Ovarian cancer is the most fatal of gynecologic malignancies, and has a 5-year survival rate of only 37 percent. While studies have linked excess body weight to higher risks of certain cancers, little is known about the relationship between body mass index and ovarian cancer risk.

Researchers studied 94,525 U.S. women aged 50 to 71 years over a period of seven years. The researchers documented 303 ovarian cancer cases during this time and noted that among women who had never taken hormones after menopause, obesity was associated with an almost 80 percent higher risk of ovarian cancer. In contrast, no link between body weight and ovarian cancer was evident for women who had ever used menopausal hormone therapy.

According to researchers, these findings support the hypothesis that obesity may enhance ovarian cancer risk in part through its hormonal effects. Excess body mass in postmenopausal women leads to an increased production of estrogen, which in turn may stimulate the growth of ovarian cells and play a role in the development of ovarian cancer.

Among women with no family history of ovarian cancer, obesity and increased ovarian cancer risk were also linked in this study. However, women that did have a positive family history of ovarian cancer showed no association between body mass and ovarian cancer risk.

The study will be published in the February 15, 2009 issue of CANCER, a peer-reviewed journal of the American Cancer Society.