By Tim Byers, MD, MPH
There are many definitions of health disparities, but my favorite is disparities are differences that should not exist. This definition reflects the social injustice in how some races and ethnicities suffer more from cancer than others.
I like this definition of disparities (or health inequity, as many people are calling it) because it can motivate us to fix the problem - the social, economic, cultural, and political barriers that keep some racial and ethnic minorities from getting cancer prevention, early detection, and state-of-the-art cancer treatment. This obviously can be harmful to racial and ethnic minorities.
But this definition is also a problem. It can cause us to focus so much on the differences that should not exist (the social and economic inequalities) that we ignore factors driving racial and ethnic differences that may actually have a positive influence on people's risk of developing or dying from cancer. Why is that important?
If we look at differences in cancer risk according to race/ethnicity we can see many examples where cancer risk, stage at diagnosis, and death rates are higher for racial/ethnic minorities. Prostate cancer and breast cancer among African Americans are clear disparities. African Americans are more likely to be diagnosed at a later stage; the cancers are more often of a more rapidly growing type; and treatments are often less aggressive; so the net result is that death rates are higher. We also see higher rates of some cancers for other racial/ethnic minority groups, such as the high risk for liver cancer among Asian Americans, and the high risk for gall bladder cancer among American Indians.
Differences that are related to more positive outcomes among minority groups get much less attention. For instance, cancer rates are much lower for most cancers among Asian Americans, Native Americans, and Hispanic Americans. We do not think of those types of differences as "disparities" because they do not have harmful effects on those minority groups. But those differences are real and important, and in most instances we do not have a very good understanding of why they occur. If we did, we might be able to use that knowledge to help bring cancer rates down for other groups, too.
Breast cancer among Hispanic women is a good example of how not focusing on differences that aren't seen as disparities can be limiting. Hispanic women have a higher proportion of estrogen-receptor (ER)-negative breast cancers than do white (non-Hispanic) women. ER-negative breast cancers are harder to treat and are more likely to be fatal. This sure looks like a disparity, but in fact, it is not. The overall risk for getting ER-negative breast cancer is the same for Hispanic and non-Hispanic white women. Thus, the higher proportion of ER-negative cancers among Hispanics is due to the fact that non-Hispanic white women have a substantially higher risk for ER-positive breast cancer. There has been little attention paid to the question of why this higher risk for ER- positive breast cancer exists among non-Hispanic white women, but there should be.
We must focus our attention on the social and cultural factors that create disparities in cancer suffering. However, as we do this we should not lose sight of the many other differences in cancer risk and outcomes that we do not regard as disparities. These "positive" differences give us some important opportunities to answer fundamental questions about why cancer happens and how it can be prevented. Why are incidence rates for most cancer sites (Cancer Facts & Figures 2012, page 44), so much lower among Asian Americans, Native Americans, and Hispanics? Genetics do not seem to explain most of those differences, so what is it about their life stories, their diets, or other cultural factors that have created such big differences?
Answers to those questions, currently being researched in numerous studies, will help us to better understand the causes of cancer, and thereby avoid the greatest disparity of all - the difference between what we could have done and what we will have done to reduce the future suffering from cancer for everyone.
Dr. Byers is on the board of directors for the American Cancer Society and is associate dean and professor for the University of Colorado School of Public Health.