Prostate Cancer (Adenocarcinoma of the Prostate)

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What is Prostate Cancer?

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The prostate is a gland found only in men. It surrounds the urethra (the tube through the penis that drains urine from the bladder), and sits at the base of the bladder. The prostate is normally about the size of a walnut.

The function of the prostate is to produce fluid that forms part of the semen. This prostatic fluid, in addition to the fluid produced by the seminal vesicles, forms the fluid which carries the sperm when a man ejaculates.

An adenocarcinoma is a type of cancer that arises in the cells of glands. Most cells in the prostate gland are of the glandular type, which means that adenocarcinoma is the most common type of cancer to occur in the prostate. Cancer occurs when the genes of a cell become abnormal (mutation), causing the cell to multiply and interfere with the normal function of a tissue.

Once the cancer reaches a certain size, the abnormal cells can spread to other parts of the body and cause cancerous tumours to grow. This phenomenon is known as metastasis. If a tumour is capable of spreading to other parts of the body in this way, it is called malignant. Adenocarcinoma of the prostate is malignant, however many types grow extremely slowly, and so are unlikely to spread before a man dies of other causes.

Male urogenital system

Who gets Prostate Cancer?

Prostate cancer is the sixth most common cancer in the world and the most common form of cancer in Australian men (after nonmelanoma skin cancer). One in six men will develop prostate cancer at some point in their lives. One in 34 will die from it, making it the second leading cause of death in Australian men. Although prostate cancer is the second most common cause of cancer in Indigenous Australian males (after lung cancer), the rates are lower in Indigenous men than in non-Indigenous men.

There has been a significant increase in the rates of diagnosed prostate cancer since screening asymptomatic men became popular in the 1990s. This screening is carried out via Prostate Specific Antigen (PSA) testing.

Virtual Medical Centre Video

Watch a video on Diagnosis and Treatment of Prostate Cancer

Predisposing Factors

Age

The main risk factor for prostate cancer is age. Prostate cancer is rarely diagnosed before the age of 40. After 40, the incidence rises rapidly. PSA testing is not generally carried out on men aged under 50 unless they have significant risk factors. The rates of prostate cancer at different ages are as follows:

Age
(years)
Percentage of men
with prostate cancer
20–30
2–8%
31–40
9–31%
41–50
3–43%
51–60
5–46%
61–70
14–70%
71-80
31–83%
81–90
40–73%

Genetics

Around 5–10% of prostate cancer is due to genetic defects, so men who have a family history are more at risk of developing it themselves. Men who have a first degree relative (brother, father, son) who have had prostate cancer are two or three times more likely to develop prostate cancer themselves. This risk may be higher if the relative was diagnosed before the age of 60.

Identifying particular genes involved in prostate cancer has proved challenging. The BRCA1 and BRCA2 genes are associated with having a two to five times higher risk of prostate cancer.

Race

In American studies, Black men have higher rates of developing prostate cancer than White or Hispanic men. Indigenous Australians are at lower risk of being diagnosed with prostate cancer than White Australians.

Lifestyle

In Caucasians, smoking has been linked to a greater number of deaths due to prostate cancer.

Obesity may be linked with more aggressive forms of prostate cancer, but not with an increased incidence. The link between prostate cancer and diet has been extensively studied. Important findings include:

A diet high in animal fat may contribute to prostate cancer;
A diet low in vegetables may be a risk factor for prostate cancer; and
Soy intake may have a modest protective effect against prostate cancer.

Other

Other men who are at increased risk of prostate cancer are those who have had high PSA levels, or abnormal prostate biopsies in the past.

In the past, testosterone levels were thought to be related to the development of prostate cancer, but this does not appear to be the case.

Progression

In many cases, prostate cancer spreads so slowly that it never causes illness, and the patient will often die of other causes before the cancer can cause death. However, if the cancer is left untreated, it is possible that it will spread to local pelvic lymph nodes, and eventually spread to other parts of the body (metastasise). This may eventually result in organ failure and death. Bony metastases from prostate cancer are common. For men who choose not to undergo definitive local treatment, their likelihood of survival relates to the aggressiveness of the prostate cancer.

Without treatment, the 10 year disease-specific survival of men with grade 1 prostate cancer (Gleason score 2 to 4) is 87%, with metastases present in 20%. Of men with grade 2 cancer, 42% develop metastases at 10 years. Ten year survival with grade 3 prostate cancer (Gleason 5 to 7) is 34% without treatment.

Another study found that 40% of men who did not have treatment for their prostate cancer died from the disease after fifteen years. About 80% of men who chose radical prostatectomy survived.

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