While cancer survival rates in the USA have increased significantly over recent decades, African Americans continue to lag behind whites. In 2003, overall 5-year cancer survival rates were 68% for whites and 59% for African Americans. For most cancer sites African Americans have the lowest survival rates of all ethnic groups.
The death rate for all cancers combined is around 30% higher in African American men and 15% higher in African American women compared to their white counterparts. For prostate cancer, death rates are a massive 145% higher in African American men compared to white men.
5-year survival differences are greatest for oral cancers (62.4% whites vs 42.1% African Americans), melanoma (90.9% vs 72.4%), and breast cancer (90.4% vs 77.0%). Of the major cancer sites, only stomach cancer carries a better prognosis for African Americans compared to whites.
The graph below shows the differences in 5-year survival rates between African Americans and whites across the most common cancer sites.
There are several reasons for the differences in cancer survival, these are discussed in more detail below.
Stage Of Cancer At Diagnosis
African Americans are disproportionally represented in lower socio-economic groups. There is a strong link between scio-economic status and stage of cancer at diagnosis. Poorer people are less likely to participate in screening programs that may pick up cancer early. They also tend to ignore the early warning signs of cancer, resulting in a longer time from first symptoms to diagnosis.
As can be seen from the graph, a significantly higher percentage of cancers have already metastasized to distant locations in African Americans compared to whites. In African Americans, 8% of breast cancers, 24% of colorectal cancers, and 60% of lung cancers are diagnosed at an advanced stage while the corresponding numbers for whites are 4%, 19%, and 56%. This has a huge impact on overall survival rates because cancer with distant metastases almost always have a poor prognosis. For example, advanced breast cancer carries a 5-year survival rate of just 23% compared to 98% for localized tumours that haven’t spread beyond the breast.
There are significant differences in cancer care across different ethnic groups. African Americans tend to receive less aggressive cancer therapies, are less likely to enrol in clinical trials, and are more likely to refuse cancer treatment altogether. Lower socio-economic status, lack of insurance cover, and greater distance to health-care facilities appear to be major factors in treatment differences.
A 2002 review, published in the Journal of the National Cancer Institute, looked at racial differences in cancer treatment. The researchers found that African Americans were less likely to receive treatment for lung cancer and were less likely to undergo surgery, the only curative treatment option for non-small-cell lung cancer. African Americans were also around 30% less likely to receive palliative chemotherapy, even when they had the same insurance cover as whites. Significant treatment differences were also observed for breast, cervical, colorectal, and prostate cancer.
Vitamin D Status
Vitamin D deficiency is more prevalent in African Americans because darker pigmentation results in decreased endogenous production of vitamin D. Low vitamin D levels have been linked to a poorer prognosis for several forms of cancer including colorectal, breast, and lung cancer.
One study, published in 2006, used data from the Health Professionals Follow-Up Study to examine the effect of vitamin D status on cancer risk and mortality. The researchers found that every 25 nmol/L increase in 25(OH)D levels (a measure of vitamin D status) was associated with a 17% reduction in cancer incidence and a 29% reduction in cancer mortality. The fact that mortality was more strongly linked to vitamin D status than incidence implies that while vitamin D may lower the risk of developing cancer, it also increases the probability of survival in those diagnosed with cancer.
Low Dose Aspirin Usage
Recent research has linked regular low-dose aspirin use with a lower risk of developing cancer as well as a slower spread of cancer once it has been diagnosed. A study, published earlier this month in The Lancet, found that among individuals taking low-dose aspirin regularly, the risk of cancer metastasizing to distant locations was reduced by 36%. Aspirin had the largest effect on adenocarcinomas which includes most colorectal cancers and slightly under half of lung cancers. Regular aspirin users who were diagnosed with adenocarcinomas were half as likely to die from the disease compared to those who did not take low-dose aspirin.
Low-dose aspirin usage is lower in African Americans than in whites. A 2011 study, using data from the Multi-Ethnic Study of Atherosclerosis (MESA) which involved 6,814 middle aged Americans, found that the prevalence of low-dose aspirin use in whites was 19%, 25%, and 38% for those at low, medium, and high risk for heart disease respectively. The corresponding rates in African Americans were just 11%, 14%, and 25%.
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