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The prostate is an exocrine (secreting) gland in the male reproductive system. It surrounds the urethra just below the bladder and can be felt indirectly behind the rectal wall by a finger inserted into the rectum (this is known as digital rectal examination or DRE). A healthy prostate is slightly larger than a walnut. The prostate stores and secretes a milky fluid that makes up 25–30% of the semen volume, along with spermatozoa and seminal vesicle fluid. Prostatic fluid is expelled in the first ejaculate together with most of the spermatozoa.
Three main diseases can afflict the prostate: prostatitis, benign prostatic hyperplasia (BPH) and less commonly, prostate cancer.
Prostatitis is inflammation of the prostate gland. Prostatitis is a very common problem, which occurs particularly, but by no means exclusively, in older men [37]. Typical symptoms of prostatitis include fever, chills, increased urinary frequency, frequent urination at night, difficulty in urinating, burning or painful urination, pain between the anus and the scrotum (perineal pain), low-back pain, a tender or swollen prostate, blood in the urine, and painful ejaculation.
The best understood cause of prostatitis is infection with the same kinds of bacteria that cause other kinds of urinary tract infection. Acute bacterial prostatitis typically affects younger men, or those 22with a urinary catheter, and often causes severe symptoms. Chronic prostatitis typically affects middle-aged or older men, often causes few symptoms, and is typically found as a cause of recurrent urinary tract infections. Bacterial prostatitis is treated with antibiotics.
Chronic non-bacterial prostatitis or male chronic pelvic pain syndrome, is the diagnosis given to the 95% men who have some symptoms of prostatitis, but no evidence of bacterial infection [38]. Many treatments have been tried for this poorly understood set of symptoms, but those tested carefully, including with alpha blockers, anti-inflammatories, and alternative therapies, have shown only modest benefits at best [39].
Benign prostatic hyperplasia (BPH) occurs in older men. With ageing, the prostate often enlarges to the point where urination becomes difficult. Symptoms include needing to urinate often or delayed commencement of urination. If the prostate grows too large, it may constrict the urethra and impede the flow of urine, making urination difficult and painful, and in extreme cases completely impossible. The prostate gets larger in most men as they age. A large European study showed the prevalence of BPH is 2.7% for men aged 45–49, increasing to 24% by the age of 80 [40].
BPH can be treated with medication, a minimally invasive surgical procedure or by surgery that completely removes the prostate. Minimally invasive procedures include transurethral needle ablation of the prostate (TUNA) and transurethral microwave thermotherapy (TUMT). The surgery most often used for obstructive BPH is called transurethral resection of the prostate (TURP or TUR). In TURP, a surgical instrument is inserted into the penis through the urethra and small sections of the prostate that are pressing against the upper part of the urethra and restricting the flow of urine are shaved off from the inside, reducing the pressure on the urethra. The procedure is often colloquially known as a “rebore”. 23
Prostate cancer is a common cancer, affecting about 20% of men by the age of 85. It is uncommon in young men (under 50) and becomes increasingly common as men age. In fact, autopsy studies show that a significant proportion of men (around 40–50%) – have prostate cancer by the age of 70. These men had no idea they had prostate cancer, so we know that prostate cancer occurs commonly and can cause no symptoms at all. Prostate cancer is the cause of death in only about 4% of men. Since it occurs in up to 50% of men, we therefore know that in many, many men it is not life threatening (see below).
Early prostate cancer causes few symptoms. In fact there are no symptoms that can differentiate prostate cancer from benign prostate diseases such as benign prostatic hyperplasia. Just like BPH it can cause problems with urination and erectile function.
Usually prostate cancer grows very slowly (see indolent cancer below) but what we call “prostate cancer” includes a spectrum of disease from slow-growing cancers through to rarer cancers that grow and spread more rapidly. Prostate cancer cells may metastasise (spread or disseminate) from the prostate to other parts of the body, such as the lymph nodes, bones, lungs and liver. Prostate cancer cells that spread to other parts of the body can cause significant symptoms, most commonly bone pain and fatigue. Prostate cancer that has spread to other parts of the body is incurable and usually fatal, but it is also treatable so that unpleasant symptoms can be reduced. Most men with metastatic prostate cancer live several or more years after it is diagnosed.
“Indolent” means slow growing. Many may be surprised to learn that cancer can exist in the body for many years without ever becoming a problem. Thyroid cancer and lymphomas are examples 24of cancers which are found in people but can be indolent and nonlife threatening. We know from autopsy studies that they may exist in the body for many years without causing any problems to a person. More on autopsy studies shortly.
In the past 30 years in the US, the incidence of thyroid cancer doubled while the death rate from the disease remained stable [41]. As we will see in detail later, this is also the case with prostate cancer: nearly all of this large increase in cancer incidence – 87% with thyroid cancer – can be explained by advances in diagnostic and imaging technology that enable thyroid cancer to be discovered. These developments have seen small papillary cancers being found that would have not been found with earlier diagnostic techniques. As diagnostic technology becomes more and more sophisticated and precise, evidence of disease can be found that in past times would have not come to light.
With prostate cancer, massive increases in the number of men being tested for the disease have resulted in large increases in the incidence of the disease. But just like thyroid cancer, the death rate from prostate cancer has remained remarkably stable for nearly 40 years in Australia.
Some reading this will immediately think “isn’t it wonderful that advances in science have allowed us to detect these cancers earlier, so they can be treated sooner and save lives.” Such thinking risks missing the point that the whole aim of medical investigation is to find and treat problems which threaten health and life. If a “problem” does neither, we need to ask why it should be thought of as a problem. The authors of the thyroid study above commented that “many of these cancers would likely never have caused symptoms during life” and the burgeoning incidence of thyroid cancer is a classic example of “overdiagnosis” [41]. 25
Overdiagnosis means the diagnosis of conditions which would have never caused a person distressing problems of ill-health or death. It means conferring a disease label on people who are living lives untroubled by that disease and more importantly, who are unlikely to be ever troubled by that disease. Prostate cancer has been described as the par excellence example of overdiagnosis. This does not mean that there are not men whose lives are saved from early death from prostate cancer by early diagnosis. But as we shall see throughout this book, we have little way of knowing in advance which men will benefit from screening and which will be unnecessarily treated, often with serious adverse consequences to their life. The fundamental problem is that by screening and testing for prostate cancer we are finding many more prostate cancers than we ever did before, and strange as it may seem, many of these cancers would never become life threatening. In the past these men would never have known they had prostate cancer, they would go on to die of something else, dying with their prostate cancer, rather than because of it. By finding all these prostate cancers that are indolent we are giving many more men a prostate cancer diagnosis than ever before. Hence the term “overdiagnosis”. This is the core dilemma that each man contemplating being tested faces.
One way of estimating the extent of overdiagnosis in a community is via the results of autopsies carried out on people who have died while not under medical care. Autopsies are performed to determine cause of death when this has not already been established by diagnosis prior to death occurring, but can also reveal the presence of symptomless disease that was not causing the person any problems. These studies provide a unique way of estimating the prevalence of undiagnosed, often benign disease in a population. This is because people who die suddenly, while not being a random sample, nonetheless represent 26a wide cross-section of the population. Sudden deaths may occur more in men with dangerous occupations and who have risk factors for heart disease. These factors may introduce unknown biases that might cause the prevalence of prostate cancer to be lower or higher than in a truly random sample of the population. But the nature and direction of such biases are not obvious, and so it is likely that the picture we get from autopsy studies will provide a broadly accurate estimate of the prevalence of undetected prostate cancer in the community. Because we can compare the prevalence of symptomless prostate cancer found at autopsy with how many men develop prostatic cancer that causes symptoms and then die of it, we can get a broad estimate of the extent of overdiagnosis. In other words, autopsy studies can show us that there are some diseases which commonly don’t cause symptoms at all, much less threaten life. And the prevalence of such disease is quite high.
Autopsy studies of Chinese, German, Israeli, Jamaican, Swedish, and Ugandan men who died of other causes (such as sudden death through injury, homicide, suicide or heart attack) have found prostate cancer in 10–20% of men in their 50s, and in a remarkable 40–50% of men in their 70s [42]. In a Pittsburgh (US) study of 340 sudden death victims who had donated their organs for transplantation, it was found that across all age groups combined, 12% of men had prostate cancer. From age 40, the proportion of men with evidence of the disease began to rise. Among men aged 50–59, 23% had incidental prostate cancer and among those aged 60–69, 35% (approximately one in three) had incidental prostate cancer. In the oldest group (aged 70–81) 46% of men were harbouring the disease [43].
These studies provide a unique way of estimating the prevalence of undiagnosed, often benign disease in a population. The take-home message from these studies is that benign, symptomless prostate cancer is very common in men, especially in later life. Men live without knowing they have the disease and most will never be affected adversely 27by it, dying of some other cause with “silent” prostate cancer having been in their bodies for many years. As prostate cancer did not kill these men, it is clear that finding and treating their prostate cancer would not have delivered any health benefit, nor extended their lives.