greater risk. African Americans have the poorest prognosis for some cancers.
Simon Jarratt / Corbis
For years, researchers know that race is a factor in cancer survival. Black women are less likely than whites to have breast cancer, for example, but much more likely to die from it ( Science , February 2, 07). How much of this difference stems from unequal access to health care, such as regular screening and aggressive treatment, and how much is rooted in biology? A new study looks back on dozens of clinical cancer trials finds that for some cancers, such as lung and leukemia, race makes no difference, while for others, such as breast, prostate and ovarian cancer, it does.
oncologist Kathy Albain of Loyola University of Chicago in Illinois found that one way to get a big-picture view of the link between race and cancer survival was combing through a vast clinical trials network. So she turned to the Southwest Oncology Group (SWOG), one of the many cooperative groups in the United States overseeing large multicenter trials for a variety of cancers in which all participants receive the same level of care, and many receive the same treatment. Albain and colleagues focused on 35 large SWOG trials that were running at some point between 1974 and 01, which included almost 20,000 adults. Trials were conducted on eight cancers: breast, lung, colon, ovarian, prostate, multiple myeloma, lymphoma and leukemia. Albain's team examined how African-American participants are doing, adjusting for potential confounding factors such as weight and socioeconomic status (estimated from zip codes).
For most cancers, the race made no difference in survival. But for three - breast, prostate and ovarian cancer - it mattered. In premenopausal cancer early breast, for example, the survival rate at 10 years was 68% for African Americans against 77% for all other patients (mostly Caucasian) in the tests. For advanced ovarian cancer, median survival was 1.3 years for African Americans and 2.3 years for the rest of the participants. And cancer advanced prostate, it was 2.2 years against 2.7 years, the group says online today in the Journal of the National Cancer Institute .
First, the results are reassuring because for many common cancers, race made no difference to the outcome, said Albain. She believes the answer to why there are differences in three cancers lies in an interaction between tumor biology, hormonal responses in the patient, and genes that may affect how medicines such as some chemotherapy, are metabolized .
One of the issues that dogged the study of racial disparities in cancer has been how much is due to access to care, notes Timothy Rebbeck, a cancer epidemiologist at the University of Pennsylvania . But here, "the disparities persist even with standard treatment." In addition, three specific cancers sex were fingers in other racial-disparity studies, he said.
One concern, said Peter B. Bach, a physician and epidemiologist at Cancer Center Memorial Sloan-Kettering in New York City, is whether the deaths in the trials were invariably due to cancer - as opposed to a disease unrelated to which African Americans are more susceptible, such as diabetes. But Albain noted that if that were the case, his group would have seen disparities in all cancers - not just some detected. She is now scrutinizing the expression profiles of genes and other characteristics of tumor bank for more tips.
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