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Epidemiology of Prostate Cancer

US Oncology Review, 2005;1(1):1-6 DOI: http://doi.org/10.17925/OHR.2005.00.00.1f

Abstract:

Abstract
Prostate cancer is a common condition worldwide. Different geographical regions have varying incidence and mortality. Globally, prostate cancer is the sixth most common cancer, and the third most common cancer in men in developed countries.The risk of prostate cancer is increased by African-American ethnicity, increasing age, positive family history, and other factors such as diet. Nonetheless, the causes of prostate cancer are not well understood compared with other common cancers like lung and breast cancer.

The introduction of prostate-specific antigen (PSA) screening made an enormous impact on the incidence of prostate cancer, which increased in the early 1990s and is currently down to pre-PSA screening levels. Screening has caused a change in pattern of disease to an earlier stage but not lower grade. Death rates due to prostate cancer diminished in the 1990s due to a decrease in advanced cases with distant metastasis.

Introduction
About 9.7% of cancers in men are due to prostate cancer; in developed parts of world it increases to 15.3% and in the underdeveloped world it only accounts for 4.3%.1 In the US, the most commonly diagnosed cancer in men is prostate cancer and it is the second most common cause of death after lung cancer. The American Cancer Society estimates that by the end of 2004, about 230,110 new cases of prostate cancer will be diagnosed in the US. One in six men will be diagnosed with prostate cancer, and one in 32 will die of prostate cancer. It is estimated that 29,900 men in the US will die secondary to prostate cancer in 2004.2 Incidence of prostate cancer is highest in the US, Canada, and Scandinivia, and lowest in China and Asian countries.3 This variation could be due to different genetic predisposition, differences in diet, variation in quality of healthcare, and deficiencies in cancer registration; or it could be due to multiple factors mentioned above. Prostate cancer is a disease related to older age as it is very infrequent below the age of 40 but very common above 65. It is estimated that by 2030, with an increase in the proportion of people over 65 to from 12.4% 19.6%, the number of prostate cancer cases will quadruple.4 Funding for prostate cancer has increased in recent times and hopefully this will shed more light on its causes and help to devise prevention strategies.

Predisposing Factors

Age
Aging increases the risk of prostate cancer. Under 40 years old, prostate cancer is rare but over 65 years of age it is very common, accounting for 70% of cases in US.5 The lifetime risk of being afflicted with prostate cancer is 1:6. The possibility of having prostate cancer varies with age, being 13.7% for the age group 60–79 years, 2.2% for those aged 40–59, and 0.005% in those younger than 39 years. The probability of finding prostate cancer when performing autopsies in deceased people is much higher, at about 20% in men between the ages of 50 and 60 years and increasing to 50% in men between 70 and 80.The risk of having pathological evidence of prostate cancer in a 50-year-old man is 42%, the risk of it clinically becoming manifest is 9.5%, and risk of mortality is 2.9%, indicating a high degree of prevalence of sub-clinical disease.7

Race
Asians have the lowest incidence rates of prostate cancer at about 107.2 per 100,000, Hispanics have a slightly higher rate at 127.6 per 100,000,Whites have a rate of 172.9 per 100,000, and African-Americans have the highest rates of 275.3 per 100,000 – about 60% higher than Whites.The death rates also vary between different races, with data from 1992–1999 showing that African- Americans have a ratw five times higher than Asians, three times higher than that of Hispanics, and twice that of Whites.African-Americans are more likely to present with advanced disease than Whites as per results from the Surveilance, Epidemiology and End Result (SEER) program of the National Cancer Institute, but there is no difference in grade.8 Five-year survival rates for African- Americans have improved over the last 30 years but are still less than Whites, at 93% versus 98%.9 Recently, a study based on incidence-based mortality rate (IBM), which takes mortality rate and goes back in time to assess various factors associated with diagnosis of disease, showed that higher mortality in African-Americans may be due to reporting with advanced-stage disease, and not due to a difference in the number of primary tumors or treatment. This approach is different from the survival approach, where a specific group with disease is followed to their eventual vital status.10

Familial Factors
There is an increase in incidence of prostate cancer in persons with a history of prostate cancer in their family – about two to four times higher than in control populations. Those with a family history of prostate cancer tend to have their disease diagnosed six or seven years earlier than controls.11 Family history and hereditary factors are estimated to be important in 5% to 10% of all prostate cancers, and 40% of those cancers diagnosed below the age of 55.The clinical presentation of familial prostate cancer is not sporadic in cancer in presenting at an earlier age, and there is no difference in stage or grade. The factors responsible may be an inherited gene or exposure to a similar environmental factor, or it may simply be that as it is a common disease, it is due to chance alone.