Black-white cancer mortality gap starts with incidence rates

Targeting prevention activities could help minimize these differences.

By Victoria Stagg Elliott — Posted April 13, 2009

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African-Americans have a higher cancer death rate than Caucasians, and this circumstance largely appears to be due to discrepancies in the incidence numbers for this disease, according to a paper in the Feb. 3 Journal of General Internal Medicine.

"[African-Americans] are more likely to get cancer in the first place," said Mitchell Wong, MD, PhD, lead author and associate professor of general internal medicine and health services research at the University of California, Los Angeles.

Researchers created a model to analyze data from the National Cancer Institute's Surveillance Epidemiology and End Results registry (SEER) and the Centers for Disease Control and Prevention's National Health Interview Survey. Differences in how often cancer was diagnosed played a much larger role than survival rates or the stage the disease was detected for all cancers except those affecting the prostate and breast. This work is part of a trend in health disparities research to identify where resources could make the biggest impact.

"The field of racial disparities research is ready to go beyond studies that show that disparities exist, or even why disparities exist, to fixing the problem," Dr. Wong said. "We want to help people understand where their intervention should be targeted."

The authors suggest putting money toward preventive strategies such as those aimed at reducing smoking and obesity, both of which are common issues among African-Americans. Such action, they say, may go a long way toward closing the mortality gap. Many experts agree.

"Preventing smoking and preventing lung cancer would have the greatest impact on the disparities on lung cancer-related diseases," said Ken Chu, PhD, chief of the disparities research branch at NCI's Center to Reduce Cancer Health Disparities.

Health disparities work also is starting to examine in the context of this mortality gap the role played by inherent biological differences in the individual or the tumor.

For instance, another pair of studies explore specific ways these factors may contribute to the outcomes. The more recent one, published in the April 1 Clinical Cancer Research, found that African-Americans with colon cancer were more likely to be homozygous for the p53 Codon 72 polymorphism. This genetic presence was associated with a reduced chance of survival. The second paper, which was published in the March 25 Breast Cancer Research, found that African-American women were more likely to have tumors that were negative for all three hormone receptors. This finding means that their disease is harder to treat.

Efforts continue

Disparities have long been a concern for government agencies and medical societies, including the American Medical Association. The AMA recognizes racial and ethnic health disparities as a barrier to effective medical diagnosis and treatment. The AMA also adopted policy in 2008 encouraging that research and funding be directed to racial and ethnic disparities among minority women with regard to cancer screening, diagnosis and treatment.

"Disparities in care based on race remain a major public health concern, as evidenced by findings of this study [in the Journal of General Internal Medicine]," said AMA Board Chair Joseph M. Heyman, MD. "Along with our partners, the AMA is working to eliminate disparities through our work with the Commission to End Health Care Disparities and the Minority Affairs Consortium."

But those working to reduce health disparities also expressed concern that the study may have oversimplified the impact of persistent differences in access to care. According to a study in the February 2008 Cancer, which analyzed Medicare treatment data for colorectal, breast, lung and prostate cancer, racial disparities changed little from 1992 to 2002.

"I'm troubled by [the study in the Journal of General Internal Medicine]. There's a lot of information that doesn't connect with what I think is reality," said Dr. Derek Raghavan, chair of the Cleveland Clinic's Taussig Cancer Institute. "They used the SEER program data. It has some really good elements to it, but the quality of the data is a little bit variable. The SEER data may not have been the appropriate quality of data for the question they asked."

As another argument for the role of access to health care, critics of the paper pointed out that disparity gaps tend to widen when screening or treatment becomes available.

"When you look at breast cancer, and you go back to the 1970s before we had screening and before we had more advanced treatment, there really was not that much of a difference in mortality," said Len Lichtenfeld, MD, deputy chief medical officer of the American Cancer Society. "Then disparities started to widen. This suggests that we need to pay better attention to access to care."

Dr. Raghavan co-chairs the American Society of Clinical Oncology's health disparities advisory group. A white paper from this body on disparities in cancer care is due to be published in the Journal of Clinical Oncology at the end of April.

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Disparities in cancer mortality

[download pdf]

African-Americans are more likely than Caucasians to die of cancer. Research suggests that a large part of this difference may be due to disparities in incidence rates. Here is how the death rate and incidence rate per 100,000 changed over three decades.

Death rate Incidence rate
Caucasians African-Americans Caucasians African-Americans
1975 196.3 235.5 402.2 426.3
1980 203.3 256.2 419.4 467.2
1985 207.3 268.1 453.3 488.2
1990 210.4 279.3 488.4 520.5
1995 206.1 269.5 481.1 540.0
2000 196.3 248.0 493.4 521.9
2005 182.7 224.1 466.0 480.2

Source: Surveillance, Epidemiology, and End Results Program database, National Cancer Institute (link)

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Why are there racial disparities in cancer death rates?

Objective: Quantify the role of differences in cancer incidence, stage of diagnosis and survival rates to the differences in mortality from this disease for African-Americans and for Caucasians.

Method: Researchers created a stochastic model to analyze data from the National Cancer Institute's Surveillance, Epidemiology and End Results registry and the Centers for Disease Control and Prevention's National Health Interview Survey.

Results: African-American men and women, respectively, live 1.47 and 0.91 years less than do Caucasians because of disparities in cancer death rates. For men, cancer incidence causes 1.12 years of this gap. The stage of diagnosis is associated with another 0.17 year in disparity and survivorship accounts for the remaining 0.21 year. With regard to women, imbalance in incidence causes 0.41 year of this disparity. Differences in stage of diagnosis leads to a loss of 0.26 year. Distinctions in survival rates can be linked to a reduction of 0.31 year. When broken down by type, differences in survival numbers made a significant impact on breast and prostate cancer but not other carcinomas. Because this is a statistical model, the numbers overlap slightly.

Conclusions: Efforts to reduce differences in life expectancy should target cancer prevention, possibly through smoking cessation, and issues that affect survival from breast and prostate cancer.

Source: Journal of General Internal Medicine, Feb. 3 (link)

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External links

"The Contribution of Cancer Incidence, Stage at Diagnosis and Survival to Racial Differences in Years of Life Expectancy," abstract, Journal of General Internal Medicine, Feb. 3 (link)

"Racial and Ethnic Disparities in Health Care," American Medical Association Council on Scientific Affairs, December 2002 (link)

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