The study, published online on Aug. 28 in the American Cancer Society's journal Cancer, showed that obesity affected survival rates, shortened the length of time to recurrence of the disease, and led to earlier death from the cancer than for women diagnosed at their ideal body weight.
"This study is the first to identify weight as an independent factor in ovarian cancer in disease progression and overall survival, suggesting that there is an element in the fat tissue itself that influences the outcome of this disease in obese women," said Andrew Li, M.D., the study's principal investigator at Cedars-Sinai's Women's Cancer Research Institute at the Samuel Oschin Comprehensive Cancer Institute.
Ovarian cancer, one of the most lethal cancers, affects almost one in 60 women. Most will be diagnosed with advanced disease, and 70 percent will die within five years. There are several types of ovarian cancer, but tumors that begin with the surface cells of the ovary (epithelial cells) are the most common type. While previous studies have shown that obesity is a factor in the development and prognosis of cancers such as breast, uterine and colorectal, the nature of the relationship in ovarian cancers has been less well understood. Obesity is defined as a Body Mass Index (BMI) of 30 or above.
In this study, Li and his colleagues examined data from 216 patients with epithelial ovarian cancer to identify relationships between obesity, ovarian cancer, tumor biology and outcome. Comparison of the obese women (35 of 216) to ideal-weight women (108 of 216) showed 29 percent of the obese women and 10 percent of normal-weight women had localized disease. However, obesity was shown to have a significant effect on both the recurrence and mortality of women with advanced disease. The cellular characteristics of the tumors found in the two groups also appeared to be different.
"While further molecular studies are warranted, our study suggests that fat tissue excretes a hormone or protein that causes ovarian cancer cells to grow more aggressively," said Li, who is also a physician in the Department of Obstetrics and Gynecology at Cedars-Sinai Medical Center. "The next steps will be to examine this relationship more closely, and to determine the exact biological mechanisms that influence tumor growth in ovarian cancer."
Obesity, which affects more than 30 percent of adults 20 years or older in the United States -– more than 60 million people, according to a 2004 article in the Journal of the American Medical Association -- is a growing health concern. Recently linked to many types of cancer, obesity has already been linked to several serious medical conditions, including heart disease, diabetes and asthma. Studies have shown that a person who is 40 percent overweight is twice as likely to die prematurely compared to an average-weight person.
"The Women's Cancer Research Institute (WCRI) is dedicated to eradicating cancer as a threat to women in the United States and throughout the world," said Beth Karlan, M.D., director of the WCRI and a co-author on the study. "Studies such as this one increase our understanding of the disease and move us closer toward this goal."
Additional co-authors of this research paper, "Effect of Obesity on Survival in Epithelial Ovarian Cancer," include James C. Pavelka, M.D., Rebecca S. Brown, M.D., Ilana Cass, M.D., Ronald S. Leuchter, M.D., and Leo D. Lagasse, M.D.
Hedley AA, Ogden CL, Johnson, et al. Prevalence of overweight and obesity among U.S. children, adolescents, and adults, 1999-2002. JAMA, 2004. 291:2847-50
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