African-Americans Suffer More Cancer Deaths

Continued research is finding that African-Americans face higher risks of serious cancers and lower cancer survival rates compared with other races.

Many theories have been proposed, from delayed diagnosis to increased average body mass index, reduced intestinal bacteria and reduced intake of vitamin D from the sun.

CDC cancer study

The CDC’s National Cancer Institute published its most recent cancer incidence and mortality rates in the U.S. through 2008. They found that on a combined age-adjusted basis, U.S. blacks have a higher cancer incidence than any other race including whites, at nearly 600 per 100,000 for all cancers. Whites have a rate of 523 per 100,000, while all races have a rate of 532 per 100,000. Hispanics have an all-cancer rate of 404 per 100,000, while Native Americans only have a 293 cancer incidence per 100,000.

The data translate to blacks having about a 25% higher risk of death from cancer.

More U.S. blacks die from cancer than any other U.S. race. About 280 per 100,000 U.S. blacks die from cancer while 213 U.S. whites die from cancer. White women have a slightly higher cancer incidence, but more African-American women will die from cancer on a population basis. And black men have significantly higher deaths from prostate and colorectal cancer.

Standout differences between whites and blacks in cancer deaths include respiratory-related cancers – with 84 (blacks) versus 66 deaths (whites) per 100,000 – and prostate cancer, where the death rate per capita is over double for black men than white men, at 50 per 100,000 versus 21 per 100,000 for whites.

Black women and cancer

Black women also suffer more deaths from breast cancer per capita, at 31 per 100,000 black women versus 22 deaths per 100,000 white women.

Illustrating this higher incidence of more serious cancers and lower survival rates between blacks and whites, researchers from the Medical University of South Carolina recently determined that African American women have higher rates of recurrence and death from triple-negative breast cancer. The researchers investigated 209 randomized patients who had triple-negative breast cancer and received chemotherapy between 2003 and 2008.

The diagnosis of triple-negative breast cancer is determined by eliminating the genetic expression of estrogen or progesterone receptors or the Her2/new gene. Typically, triple-negative breast cancer will affect younger women more often, and will be more aggressive than other breast cancers. Treatment is thus often more aggressive.

The analysis of the breast cancer outcomes of the patients found that black women had a higher rate of incidence, with an almost 43% rate. The African-American women also had a significantly higher rate of recurrence, with 42.5% recurrence versus only 7% recurrence among the Caucasian women. The African-American women were also more likely to die within the five years after their diagnosis (“five year survival rate”). Only 45% lived past five years among the African-American women, versus almost 80% among the Caucasian women.

Both groups were diagnosed at roughly the same age, in the range of 53 and 54 years old. Practically all of both groups – between 99% and 100% – received radiation treatment.

As to an explanation for the differences, the researchers considered genetic factors, smoking rates as well as lifestyle and vitamin D status. One factor they discovered was that the African American women had a higher average body mass index than the Caucasian women, at 30.4 versus 28.6 kg/m2. Another prominent finding was that African-American women were less likely to be diagnosed early. Only 31.5% of the African-American women were diagnosed at stage one, while nearly 52% of the Caucasian women were diagnosed at stage one of the disorder.

Another recent study, this one from Louisiana State University, found a higher ratio of blacks had triple-negative breast cancer, at 60% compared to 20% of a Caucasian group. This study, however, showed that the African-American women five year survival rate was much closer to the white population, at 77% versus 72% for the Caucasian women.

Less sun and fewer probiotics

Probiotics may provide some explanation in the case of higher colorectal cancer deaths among black men. The CDC research found that nearly 25 out of 100,000 black men die from colorectal cancer, compared to 15 out of 100,000 white men.

In a 2007 study published in the Journal of Nutrition, researchers found that the black men in a group of 52 men had significantly lower levels of Lactobacilli bacteria in their intestines and colons. They concluded that the results of the study “supports our hypothesis that colorectal cancer risk is determined by interactions between the external dietary and internal bacterial environments.”

Other researchers have proposed that because blacks absorb lower levels of sunlight, they have lower vitamin D levels. A recent review of research from the Cleveland Clinic Lerner College of Medicine reported that blacks tend to have lower levels of vitamin D and higher levels of type 2 diabetes. They found that type 2 diabetes was associated with higher levels of colorectal cancer as well, which produced a significant vitamin D-colorectal cancer association.

Other research has also found a connection between lower vitamin D levels and increased cancer incidence among blacks, including a 2006 Harvard study that also determined an association between lower vitamin D levels among blacks and increased cancer incidence. Multiple epidemiological studies have confirmed that higher cancer rates in general are associated with lower vitamin D levels.

Because blacks have higher skin melanin content, more exposure to sunlight is required to produce the same amount of vitamin D in the body. Some experts have estimated that as much as four times more sunlight is required, yet this is highly variable, and depends upon the melanin level of the particular persons being compared.

REFERENCES:

Christiansen N, Chen L, Gilmore J, Pechar D, Szabo S. Association Between African American Race and Triple-Negative Breast Cancer: A Retrospective Analysis by Using Results From the Georgia Cancer Specialist Database. Clin Breast Cancer. 2012 Jun 7.

Chu QD, Henderson AE, Ampil F, Li BD. Outcome for patients with triple-negative breast cancer is not dependent on race/ethnicity. Int J Breast Cancer. 2012; 2012:764570.

O’Keefe SJ, Chung D, Mahmoud N, Sepulveda AR, Manafe M, Arch J, Adada H, van der Merwe T. Why do African Americans get more colon cancer than Native Africans? J Nutr. 2007 Jan;137(1 Suppl):175S-182S.

Tsai CJ, Giovannucci EL. Hyperinsulinemia, Insulin Resistance, Vitamin D, and Colorectal Cancer Among Whites and African Americans. Dig Dis Sci. 2012 May 6.

U.S. Mortality Files, National Center for Health Statistics, CDC