Cancer affects all population groups in the United States. But certain groups may bear a disproportionate burden of cancer compared with other groups.
Cancer disparities (sometimes called cancer health disparities) are differences in cancer measures such as:
- incidence (new cases)
- prevalence (all existing cases)
- mortality (deaths)
- morbidity (cancer-related health complications)
- survivorship, including quality of life after cancer treatment
- burden of cancer or related health conditions
- screening rates
- stage at diagnosis
Cancer disparities can also be seen when outcomes are improving overall but the improvements are delayed in some groups relative to other groups.
Although disparities are often considered in the context of race/ethnicity, other population groups may experience cancer disparities. These include groups defined by disability, gender/sexual identity, geographic location, income, education, and other characteristics.
Cancer disparities are thought to reflect the interplay of socioeconomic factors, culture, diet, stress, the environment, and biology.
Members of minority racial/ethnic groups in the United States are more likely to be poor and medically underserved (that is, to have little or no access to effective health care) than whites, and limited access to quality health care is a major contributor to disparities. For example, regardless of their racial/ethnic background, the poor and medically underserved are less likely to have recommended cancer screening tests than those who are medically well served. They are also more likely to be diagnosed with late-stage cancer that might have been treated more effectively if diagnosed earlier.
The higher cancer burden in poor and medically underserved individuals may also reflect different rates of behavioral risk factors for cancer, such as higher rates of tobacco smoking, physical inactivity, obesity, and excessive alcohol intake, and lower rates of breastfeeding. In addition, individuals who live in poverty may experience higher rates of exposure to environmental risk factors, such as cancer-causing substances in motor vehicle exhaust in dense urban neighborhoods.
Even among people of higher socioeconomic status, certain racial/ethnic minority groups may experience cancer disparities. These differences may reflect cultural differences such as mistrust of the health care system, fatalistic attitudes about cancer, or apprehension or embarrassment about having certain kinds of medical procedures. They may also reflect geographic or other differences in access to quality care.
Cancer disparities may also reflect differences in clinical trial participation. Clinical trials often have low participation by racial/ethnic minorities, which raises the possibility that the results may not be fully applicable to them.
Biological differences also appear to play a role in some cancer disparities. Advances in genomics and other molecular technologies are improving our understanding of how biological differences among population groups contribute to health disparities and how biological factors interact with other potentially relevant factors, such as diet and the environment.
For example, some evidence suggests that there are genetic or other biological differences between the triple-negative breast, colorectal, and prostate cancers that arise in African Americans and those that arise in people of other racial/ethnic groups and that these differences may explain differences in incidence or aggressiveness of these cancers.
Examples of Cancer Disparities
Although cancer incidence and mortality overall are declining in all racial/ethnic groups in the United States, certain groups continue to be at increased risk of developing or dying from particular cancers.
Some key cancer incidence and mortality disparities among U.S. racial/ethnic groups include:
- African Americans have higher death rates than all other groups for many, although not all, cancer types.
- African American women are much more likely than white women to die of breast cancer. The mortality gap is widening as the incidence rate in African American women, which in the past had been lower than that in white women, has caught up to that in white women.
- African Americans are more than twice as likely as whites to die of prostate cancer and nearly twice as likely to die of stomach cancer.
- Colorectal cancer incidence is higher in African Americans than in whites. Incidence in all groups is declining, but the difference between the groups remains.
- Hispanic and American Indian/Alaska Native women have higher rates of cervical cancer than women of other racial/ethnic groups; African American women have the highest rates of death from the disease.
- American Indians/Alaska Natives have the highest rates of liver and intrahepatic bile duct cancer, followed by Asian/Pacific Islanders and Hispanics.
- American Indians/Alaska Natives have higher death rates from kidney cancer than people of other racial/ethnic groups.
- Both the incidence of lung cancer and death rates from the disease are higher in African American men than in men of other racial/ethnic groups.
Other notable examples of disparities include:
- The incidence rates of colorectal, lung, and cervical cancers are much higher in the Appalachian region of Ohio than in wealthier and more populated areas of the state.
- African American women are nearly twice as likely as white women to be diagnosed with triple-negative breast cancer, which is more aggressive and harder to treat than other subtypes of breast cancer.
- African Americans are more than twice as likely as whites to be diagnosed with and die from multiple myeloma. Blacks in the United States and Africa also have a higher incidence than whites of a disorder called monoclonal gammopathy of undetermined significance (MGUS), which can be a precursor to multiple myeloma. The difference is more pronounced in younger people.
- There are large differences among racial/ethnic groups in colorectal cancer screening rates, with Spanish-speaking Hispanics less likely to be screened than whites or English-speaking Hispanics.
- Rates of colorectal cancer deaths among those younger than 65 (“premature” deaths) are higher in states with the lowest education levels than in those with higher levels. People with more education are less likely to die prematurely of colorectal cancer than those with less education, regardless of race or ethnicity.
- Behaviors that increase cancer risk, such as smoking and drinking alcohol, may be more prevalent among lesbian, gay, and bisexual youths than among heterosexual youths.
Addressing Cancer Disparities
Because many different factors can cause cancer disparities—in particular, poverty and a resultant lack of quality medical care—addressing them is not simple or straightforward. Nevertheless, researchers are identifying ways to address the most critical factors in specific disparities and are already meeting with some success.
One approach is to specifically address access to care. For example, in 2002, seeking to address disparities in colorectal cancer among African Americans, Delaware created a statewide colorectal cancer screening program that paid for screening and treatment and made patient navigators available to coordinate screening and cancer care. By 2009, this program had eliminated disparities in screening rates, cut the percentage of African Americans diagnosed with cancer that had already spread, and almost completely abolished racial/ethnic differences in colorectal cancer incidence and mortality. Similar efforts are under way to address cancer disparities among rural populations.
Researchers are also addressing biological differences in cancers across racial/ethnic groups. For example, they are identifying genetic variants that may explain the higher risk of prostate cancer among African American men compared with white men. Researchers are also looking at other molecular differences that may explain why African American men tend to get more aggressive prostate cancers than white men. Studies of this type may eventually help identify ways to reduce risk among African American men.