Racial Ethnic Epidemiologic Statistics

The clinical incidence of prostate cancer reported by the American Cancer Society in 1997 was 66% higher among African American men than among Caucasian men.9 In the past, the clinical incidence of prostate cancer has ranged from 30 to 50% higher among African Americans than among Caucasians. Also, there have been variations among the two groups in the lifetime risk of being diag nosed with prostate cancer. In 1993, 1 of 11 African Americans was diagnosed with prostate cancer compared to 1 of 9 Caucasians. In 1996, the lifetime risk of prostate cancer diagnosis changed to 1 of 5 for both populations.10 The cause of this variation is unclear.

One variable possibly accounting for the differences noted may be differing attitudes toward screening and early detection. Taylor and colleagues demonstrated that from 1972 to 1991 prostate cancer diagnosis increased by 100% in Caucasian men but by only 40% in African American men. They reasoned that Caucasian men are more likely to take part in early detection programs and are thus more likely to be diagnosed with prostate cancer than are African American men. The study also demonstrated stage shifting, that is, men participating in early detection are more likely to be diagnosed at an earlier stage.11

One recent study of prostate cancer incidence in Nigeria suggests that risk may be grossly underestimated in that population. Osegbe prospectively studied Nigerian men aged 45 years and older who showed prostatic symptoms. The data suggested that the prostate cancer incidence rate in Nigerians may be approximately 13 times higher than commonly believed, and that the risk pool and death rate in the Nigerian population may be similar to those of African American men. The study strongly suggested that Nigeria is not a low-risk zone for prostate cancer as was previously believed, and that the clinical incidence rate among black men in the United States is similar to that found in their study. Black men in both countries share a common origin and may possibly share an inherited predisposition to prostate cancer.12

An epidemiologic study of prostate cancer in Jamaica has demonstrated that Jamaican men in Kingston have a high incidence of prostate cancer, much higher than a comparable group of African Americans. The average age-adjusted incidence rate of prostate cancer in Kingston, Jamaica, was found to be 304 cases per 100,000 men. The study examined 1121 cases of prostate cancer diagnosed from 1989 to 1994. Sources of information included the Jamaican Cancer Registry, Government of Pathology Laboratory, hospital and clinic records, and physician office records. The cancers in the Jamaican group were more advanced with greater morbidity than those in the United

States.13 There is also emerging evidence of a high incidence of prostate cancer, high-grade prostatic intraepithelial neoplasia (PIN), and worse outcome among men of sub-Saharan African descent found throughout the world, particularly in Jamaica, Nigeria, Brazil, and United States.11-15 Recently reported age-adjusted mortality rates from prostate cancer in the United States between 1991 and 1995 are approximately two times worse among African American men than among Caucasians. The age-specific mortality rate from prostate cancer is reported to be three times greater among African American men compared to Caucasians between the ages of 40 to 60 years, two times greater between 60 to 70 years, and somewhat less than two times greater over the age of 70 years16 (Table 2-1). These statistics raise several questions. Is this difference in outcome secondary to a more rapidly growing prostate cancer rate among African Americans compared to Caucasians or is it a result of delayed diagnosis among the former, accounting for the observation that prostate cancer in African Americans is often more advanced at presentation? Is prostate cancer among African Americans diagnosed at a younger age more aggressive than in the same population at an older age, and does this account for the decreasing disproportionate mortality rate among African Americans compared to Caucasians? Or is prostate cancer diagnosed among older Caucasians more aggressive than that diagnosed among younger Caucasians? It is important to understand the biology of this disease to answer these questions.

The lifetime risk of dying from prostate cancer is 3% for Caucasians and greater than 4% for African Americans.10 In spite of the consistent differences in mortality between African Americans and Caucasians, conflicting data on survival outcome have been reported. Surveillance, Epidemiology, and End Results (SEER) data from the National Cancer Institute indicate a worse stage-for-stage survival outcome for African Americans compared to Caucasians.17 Other investigators report no statistically significant stage-for-stage survival differences between the two races.18,19 However, a follow-up study recently published by one of these investigators reports a difference in stage-for-stage survival rates. African Americans were found to have a worse survival rate than Caucasians for clinically Tb-T2 PCa.20

Another study performed retrospectively examined overall survival rates among men diagnosed with prostate cancer and demonstrated an "ethnic survival cross-over" based on age: African Americans have a worse survival rate than Caucasians under the age of 65 but have a better survival rate above this age.21 At present, the cause of this phenomenon is purely speculative. In addition, this was a study of overall survival that included comorbidi-ties. It has been reported that African Americans have more comorbidities than Caucasians and that comorbidi-ties increase with age up to 77 years.22 In light of this information, the data demonstrating a better survival rate over age 65 among African Americans compared to Caucasians becomes more significant. Further investigation of survival outcomes in the two ethnic groups needs to be undertaken. Such studies should include not only race as an independent variable but also age stratified by decades. There should be a bivariate analysis of survival outcome carried out, as opposed to a univariate analysis.

Recent autopsy studies have demonstrated no statistical difference between the two races in the prevalence and initiation of the latent form of prostate cancer. One study revealed no significant differences among patients with latent cancer under the age of 50 years between the two races with regard to histologic differentiation, volume, multifocality, or anatomic distribution. Finally, the age of initiation of latent prostate cancer did not differ between African American and Caucasian males.23

Extension of the above study, however, found that high-grade PIN was more prevalent and extensive at an earlier age among African American men than among Caucasians. The presence of high-grade PIN is closely associated with aggressive prostate cancer.15 It has also been hypothesized that high-grade PIN may be a precursor to clinically significant prostate cancer. Another autopsy study demonstrated a greater volume of prostate cancer among African Americans compared to Caucasians between the ages of 40 to 49 years who died from other causes. The authors hypothesized that this fact may be responsible for earlier malignant transformation to clinically significant prostate cancer among African Americans.24 These two autopsy studies may indicate that the disease process of prostate cancer is more aggressive, with greater volume, in young African American men compared to Caucasian men of similar age.

TABLE 2-1. United States Mortality Rates, Age-Adjusted and Age-Specific Rates, by Race

TABLE 2-1. United States Mortality Rates, Age-Adjusted and Age-Specific Rates, by Race

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