Emergent trends in the reported incidence of prostate cancer in Nigeria

BACKGROUND To date there has not been any nationwide age-standardized incidence data reported for prostate cancer in Nigeria. We examined and integrated diverse trends in the age-specific incidence of prostate cancer into a comprehensive trend for Nigeria, and examined how best the existing data could generate a countrywide age-standardized incidence rate for the disease. METHODS Data were obtained from studies undertaken between 1970 and 2007 in referral hospital-based cancer registries. Records from at least one tertiary hospital in each of the six geopolitical zones of Nigeria were examined retrospectively. Data were also reported for the rural population in cross-sectional prospective studies. Age-standardized incidence rates and the annual incidence of disease were calculated. RESULTS Higher incidence rates for prostate cancer during this period were recorded for patients aged 60-69 years and 70-79 years, with a lower incidence rate for patients aged younger than 50 years. An exponential annual incidence rate of disease was observed in the 50-79 year age group and peaked at 70-79 years before dropping again at age 80 years. The results showed metastasis in more than half of these hospital-based prostate tumors. CONCLUSION Our results suggest that prostate cancer occurs at a relatively young age in Nigerians and that hospital-based registry reports may not appropriately reflect the incidence of the disease in Nigeria. A countrywide screening program is urgently needed. Finally, the difference in reported stages of disease found in Nigerians and African-Americans versus Caucasians suggests biological differences in the prognosis. Nigeria may thus typify one of the ancestral populations that harbor inherited genes predisposing African-Americans to high-risk prostate cancer.