Prostate cancer is the most common cancer affecting American men. In 2010, an estimated 217,730 men were diagnosed with it and 32,050 died of it.1 African American men are disproportionately affected, with a prostate cancer incidence two-thirds higher than whites and a mortality rate twice as high.1 Owing to such disparities, the life expectancy of African Americans is several years shorter than that of non-Hispanic whites.2
For the primary care provider, who is often the first access point for health care in the United States, it is important to understand what mechanisms may underlie these differences and what can be done to narrow the gap.3
WHAT IS THE CAUSE OF THESE DIFFERENCES?
Many studies have looked into the causes of the higher incidence of prostate cancer in African American men and their higher mortality rate from it. The disparity may be due to a variety of factors, some socioeconomic and some biologic.
Poorer access to care, or lower-quality care?
A study of US servicemen who had equal access to care showed that African American men had a higher rate of prostate cancer regardless of access to care and socioeconomic status.4
However, the 2002 Institute of Medicine report, Unequal Treatment: Confronting Racial and Ethnic Disparities in Health Care, found evidence that racial and ethnic minorities tend to receive lower-quality health care than whites, “even when access-related factors, such as patients’ insurance status and income, are controlled.”5
Some have proposed that the disparity may be a function of genetic predisposition.
Evidence of a genetic component to the high incidence and mortality rate in African American men comes from epidemiologic studies of men with similar genetic backgrounds. For example, men in Nigeria and Ghana also have a high incidence of prostate cancer, as do men of African descent in the Caribbean islands and in the United Kingdom.6
Chromosome 8q24 variants have been shown in several studies to be associated with prostate cancer risk and are more common in African American men.7–10 Some studies have also shown a higher rate of variations in cell apoptosis genes such as BCL211 and tumor-suppression genes such as EphB2 in African American men.12
These findings suggest that genetic differences may contribute to the higher prostate cancer incidence and mortality rate seen in African American men.
More-aggressive cancer, or later detection?
Not only do African American men tend to have a higher incidence of prostate cancer, they also tend to have more-aggressive disease (ie, a higher pathologic grade) at the time of diagnosis, which may contribute to the disparity in mortality rates.13–19
Initially, there was some controversy as to whether this observation is a result of genetic and biologic factors that may predispose African American men to more-aggressive disease, or if it is due to inadequate screening and delayed presentation. However, a body of evidence supports the contention that prostate cancer is more aggressive in African American men.
For example, a study of autopsy data from men who died of prostate cancer at ages 20 to 49 showed that the age of onset of prostate cancer was similar between African American and white men.20 The Surveillance Epidemiology and End Results (SEER) database showed that African American men had a higher incidence of metastatic disease across all age groups.20 A similar study conducted 10 years later confirmed that rates of subclinical prostate cancer in African American and white men do not differ by race at the early ages, but that advanced or metastatic disease occurred nearly four times as frequently in African American men.21
Another study examined prostate biopsies from African American men and found that their tumors expressed higher levels of biomarkers, suggesting they had more-aggressive disease.22
SCREENING FOR PROSTATE CANCER
Serum prostate-specific antigen (PSA) testing has become the method of choice for prostate cancer screening. However, PSA screening in asymptomatic men is under debate, because it can lead to overdetection and subsequent overtreatment of indolent disease.23
Several recent studies showed differing results from prostate cancer screening.
The US Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial found that the mortality rate was no lower with combined PSA screening and digital rectal examination during a median follow-up of 11 years than in a control group that had a lower rate of screening.24 However, further analysis of these data, with stratifying by comorbidities, showed that PSA screening in young and healthy men reduces the risk of death from prostate cancer, with minimal overtreatment.25
The European Randomized Study of Screening for Prostate Cancer found a statistically significant 20% reduction in deaths from prostate cancer with PSA screening, but that it was necessary to treat 48 men in order to save one life.26
Another study, published in 2010, showed that regular PSA screening reduced the rate of prostate cancer mortality by half over 14 years.27
African American men generally present with disease that is more advanced than in white men.28 This historically has been attributed to the fact that African Americans have been less likely to be screened for prostate cancer, though recent data indicate the gap is lessening.29–31 A cross-sectional study from the Texas Medical Center showed that 54.4% of African American men had received PSA screening, compared with 63.2% of white men.32
Another study showed that African Americans were more likely to have had a longer interval between PSA screenings before diagnosis, and that a longer PSA screening interval was associated with greater odds of having advanced disease at diagnosis.33 However, when the researchers controlled for the PSA screening interval, they found that African Americans had the same odds of being diagnosed with advanced prostate cancer as white patients did. They concluded that more frequent or systematic PSA screening may reduce the racial differences in cancer stage at diagnosis and in deaths.