Epidemiology
Prostate cancer is the most common cancer in men in the UK, with approximately 32 000 new cases per year and 10 000 deaths. More than 60% of cases occur in men over 70 years of age. Nearly 50% have metastatic disease at presentation and in a further 25% the disease presents with localised extracapsular spread. It has been estimated that for a 50-year-old man, the projected lifetime risk of histological evidence of prostate cancer is 42%, risk of clinical disease is 9.5% and risk of death from prostate cancer is 3%.
The incidence of prostate cancer increases with age; only 12% of clinically apparent cases arise before the age of 65 and only 20% of deaths occur in men under 70 years old.
Substantial increases in incidence have been reported in recent years in many countries around the world, after correction for an ageing population. Some of this may be due to a real increase in risk, but additionally the increased use of transurethral resection of the prostate (TURP) and PSA testing have increased the detection rate. In the USA, the reported incidence is up to 10 times higher than in UK, most likely due to the effect of widespread prostate cancer screening.
Aetiology and pathophysiology
Prostate cancers are mostly adenocarcinomas, with 70% occurring in the peripheral zone, 20% in the transitional zone and 10% in the central zone. Family history is a feature in 10% of cases and such patients may develop prostate cancer at a younger age. Inherited BRCA1 and BRCA2 mutations (breast–ovarian cancer families) and hereditary prostate cancers due to mutations of HPC1 (chromosome 1q24–q25) and HPC2 (chromosome Xq27–q28) have been implicated in hereditary prostate cancer (see Chapter 8). There are racial differences in the incidence of prostate cancer; the order of frequency is Black > Caucasian > Oriental. The role of diet remains controversial, although high-fat, low-fibre, smoked foods and dairy produce may increase the risk, while soya beans and retinoids appear to be protective against prostate cancer. The incidence of prostate cancer in vegetarians is 50–75% that of omnivores.
Clinical presentation
Men with prostate cancer confined to the prostate often are completely asymptomatic. Those with a large component of benign prostatic hyperplasia but transitional zone disease, often present with bladder outlet obstruction but have no other signs of prostate cancer and are diagnosed via transurethral resection.
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