African Americans have a shorter life expectancy than whites, and cancer plays a major role in this disparity. African Americans are more prone to get cancer; they tend to present at a later, deadlier stage; and they have poorer survival rates after diagnosis.
But to what extent are each of these three factors responsible for the disparity in cancer mortality? A new UCLA study, published in Journal of General Internal Medicine Feb. 18, answers that question, finding that for most types of cancer, the disparity in mortality is almost entirely due to the fact that African Americans are more likely to get cancer in the first place. Their stage at presentation and survival after diagnosis play a much smaller role.
Overall, African American men live 1.47 fewer years than white men, and African American women 0.91 fewer years than white women, due to all cancers combined. The results spotlight the need for greater prevention efforts aimed at African Americans.
This is the first time that researchers have quantified the role that disparities in cancer incidence, stage at diagnosis and survival after cancer plays in African Americans' shorter life expectancy, according to lead author Dr. Mitchell D. Wong, associate professor of medicine in the division of general internal medicine and health services research at the David Geffen School of Medicine at UCLA.
"Putting a number on it is very informative, because when you look at the figures, you see that the reason their mortality is worse is almost entirely due to the fact that blacks are more likely to get cancer," Wong said. "This highlights the importance of prevention — it's where most of the efforts should be."
A notable exception to this pattern was breast cancer. While white women are more likely to get breast cancer than African American women, the disparities between whites and blacks in stage at presentation and survival after diagnosis for breast cancer had a large impact on the racial gap in life expectancy.
"This argues for much more research and efforts to close the gap in breast cancer screening and treatment," Wong said.
The researchers analyzed data from the Surveillance and Epidemiology End Result (SEER) cancer registry and the National Health Interview Survey (NHIS). Together, the data sets covered about 2.7 million white and 291,000 African American cancer patients from 12 geographic regions in the United States: San Francisco/Oakland, Connecticut, Detroit, Hawaii, Iowa, New Mexico, Seattle (Puget Sound), Utah, Atlanta, Alaska, San Jose/Monterey and Los Angeles.
Among the other findings:
- Cancer incidence, stage at diagnosis and post-diagnosis survival accounted for 1.12, 0.17 and 0.21 years, respectively, in the life-expectancy disparity among men.
- Among women, those categories accounted for 0.41, 0.26 and 0.31 years, respectively.
- The difference in incidence of cancer had a greater impact on the racial gap in cancer mortality than did the stage at which the cancer was diagnosed.
- The differences in post-diagnosis survival were significant with only two types of cancer: breast (0.14 years) and prostate (0.05 years).
"Continuing to improve cancer treatment and screening is undoubtedly important to improving life expectancy and quality of life for all adults, yet substantial disparities in cancer mortality will persist unless we can find ways to address the enormous impact of racial differences in cancer incidence," the researchers concluded.
In addition to Wong, study authors included Susan L. Ettner and Martin F. Shapiro of the David Geffen School of Medicine at UCLA, and John Boscardin of the division of geriatrics at the San Francisco Veterans Administration Medical Center.
The National Institute on Aging, the National Center on Minority Health and Health Disparities, a Pfizer Scholars Grant in Clinical Epidemiology, and a Doris Duke Charitable Foundation Clinical Scientist Development Award funded this study.
- Wong et al. The Contribution of Cancer Incidence, Stage at Diagnosis and Survival to Racial Differences in Years of Life Expectancy. Journal of General Internal Medicine, 2009; 24 (4): 475 DOI: 10.1007/s11606-009-0912-1
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