"Poor people are at greater risk for late-stage diagnosis and have, by far, shorter survival times, regardless of race," says lead researcher Cathy J. Bradley, PhD, assistant professor of medicine at Michigan State University.

Bradley and her team examined data on 51,296 patients diagnosed in 1996 and 1997 with five cancers – breast, cervical, lung, prostate, and colon cancer. They looked at how advanced the cancers were when they were diagnosed and how long patients survived, comparing people enrolled in Medicaid to people who were not enrolled in the program. Because Medicaid is provided to people who are medically indigent, it was considered to indicate low-income status.

Biology or Income Level?

Earlier studies suggested biological differences might play a big role in survival differences between racial groups. But when the Michigan researchers analyzed race, income, and survival, they found being African American didn’t significantly increase a patient’s risk of being diagnosed late (after the cancer had spread) with cancer of the cervix, colon, or lung. The study included more types of cancer than have ever been examined together before. The researchers found being African American meant a greater chance of late diagnosis only in breast cancer, and the difference was slight in that case.

But they found people who were on Medicaid before age 65 were 1.77 times more likely than others to be diagnosed in late stages of breast cancer. The same group was 2.65 times more likely to be diagnosed with late-stage cervical cancer, 1.57 times more likely to be diagnosed late with colon cancer, and 1.59 times more likely to be diagnosed late with lung cancer.

In addition, 41% of Medicaid-insured men age 65 and older are diagnosed in later stages of prostate cancer, compared to 23% of men of the same age who are not enrolled in the program, according to the researchers.

Late Diagnosis Linked to Poorer Survival

Late diagnosis usually leads to poorer survival rates. Within two years of diagnosis, Medicaid patients under 65 were 3.3 times more likely than others to die of breast cancer. They were 2.5 times more likely to die of cervical cancer, 2.6 times more likely to die of colon cancer, 1.8 times more likely to die of lung cancer, and 2.7 times more likely to die of prostate cancer. Being African American raised the risk of death within two years only for breast cancer – to 1.5 times as great as the risk for white women.

Bradley says the study, which was done to see how the Medicaid program could improve cancer care for those it serves, shows the situation is unlikely to improve until low-income people have better access to follow-up medical care and cancer screening tests.

An American Cancer Society (ACS) expert says this research should help sort out how much of the racial disparity in cancer survival is due to factors such as income, access to medical care, diet, and smoking and how much is due to biological differences such as genetic mutations or hormone levels.

More Than One Reason

"The study demonstrated that being diagnosed at a later stage of cancer was more closely associated with poverty than race, suggesting a strong influence of income on cancer survival," says Michael J. Thun, MD, vice-president of epidemiology and surveillance research for the ACS.

"But the study also shows that African Americans with female breast cancer or colon cancer were diagnosed at earlier ages than whites. Since we know there is less cancer screening within the African-American community, that part of these results suggests biological differences may play a role also," he says.

"This study, along with others before it, suggests there is more than one reason for worse cancer outcomes among African Americans," Thun adds. "The American Cancer Society has several aggressive initiatives designed to help eliminate these very substantial disparities, and those are areas in which we continue to focus considerable efforts."