Researchers at the National Cancer Institute (NCI), part of the National Institutes of Health, report findings that suggest a biological disparity for endometrial cancer exists between Caucasians and African Americans. The research was done in conjunction with Walter Reed Army Medical Center and other institutions. Two separate studies, one examining patient outcome in four endometrial cancer clinical trials, and the other looking at gene expression patterns in endometrial tumours, provide evidence that biological factors can contribute to the significant racial disparity in survival rates for this cancer. Both studies presented at the Society of Gynaecologic Oncologists (SGO) 2005 Annual Meeting on Women's Cancer, March 19-23, 2005, in Miami, Florida, and will be published later this year.
It is estimated that in 2005 there will be approximately 40,000 new cases of cancer of the endometrium, or lining of the uterus, and about 7,000 endometrial cancer-related deaths. While the rate for new cancers in African-American women is lower than for Caucasians, African-American women have a greater mortality rate from endometrial cancer than Caucasians; an NCI 1989-1994 review reported that 5-year survival for endometrial cancer was 86 per cent in Caucasians but only 54 per cent in African Americans.
"The etiology underlying this disparity is multi-fold," said LTC Larry Maxwell, M.D., of Walter Reed's Department of Obstetrics and Gynaecology and NCI, an author of both studies. "It can include cultural differences in dealing with medical illness and unequal access to the proper care and therapy, but could also arise from a difference in biology which may result in more aggressive tumours in some populations."
Maxwell and his group sought to uncover the role of biology by examining survival outcome in a setting that should provide equal treatment to all patients: a clinical trial. The researchers studied data from four trials performed by the Gynaecologic Oncology Group (GOG), an NCI-funded cooperative group that coordinates most of the large therapeutic gynaecologic cancer studies in the United States. The survival rates for 168 African-American patients and 997 Caucasian patients with Stage III, Stage IV or recurrent endometrial cancer were compared. The analysis showed that African-American women with endometrial cancer have a 25 percent greater chance of dying than Caucasian women with the same diagnosis, and the overall median survival for African-American patients was 10.6 months compared to 12.2 months for Caucasians.
In the second study, the investigators evaluated global gene expression among endometrial cancer patients to determine any specific differences that may account for a biological disparity. Tumours from 18 African-American patients and 27 Caucasian patients were matched and compared according to stage, tumour grade, and cell type. In the initial analysis, Maxwell and his group could not identify expression profiles unique to each race. However, when they excluded early-stage cancers and focused only on advanced stage cancers, they observed expression profiles that did cluster according to race; 325 total transcripts had different expression levels in African Americans and Caucasians.
"Both of these studies suggest that underlying molecular differences may partially explain the disparity in survival outcome for endometrial cancer for these two groups," said Maxwell. He added that the studies do not imply that African Americans and Caucasians are genetically different, but rather that multiple factors including environment and culture may result in a difference in gene expression. "Further research is needed to determine how these differences can be used to help identify better therapies for high-risk minority groups."
"Though this study looks at one particular cancer in terms of racial disparities, we hope that it may shed light on our broader work in this area," said Harold Freeman, M.D., director of The NCI Center to Reduce Cancer Health Disparities.