Dr. Alfred Nougat of Columbia University Medical Center in New York City and Russell McBride of Columbia University's Mailman School of Public Health hypothesized that long-known racial differences in cancer survival between blacks and whites could be attributed to differences in tumor size and the number of lymph nodes with disease.

They analyzed clinical and demographic characteristics of 256,174 U.S. women with breast cancer -- 21,861 African American and 234,313 white -- diagnosed from 1988 to 2003 that showed that African-American women were more likely than white women to be diagnosed with tumors greater than 2.0 cm and to have at least one lymph node with disease, however, racial differences in lymph node involvement were apparent only in tumors smaller than 3.0 cm.

The study, published in the Sept. 15 issue of the journal Cancer and available online, found after adjusting for tumor size and lymph node status as well as demographic factors, African-American women were still more likely to die of breast cancer up to 56 percent higher than whites.