The prostate is a gland in the male reproductive system. Prostate cancer is the second most common cause of cancer death in men, after lung cancer. It most commonly occurs in men over 65.
The prostate is about the size of an apricot and is positioned below the bladder outlet, with the urethra (the tube that carries urine from the bladder) passing through it. It secretes seminal fluid, the nutrient-rich transport medium for sperm: about 80% of ejaculate volume is produced by the prostate.
Prostate cancer is slow-growing, and if detected early and managed correctly, survival rates are high. While the incidence of prostate cancer is rising, mortality rates are decreasing – probably because of increased awareness of routine screening. Screening does not prevent the disease, but it ensures that it is detected at an early stage, when still curable.
The exact cause of prostate cancer is not clear; there is probably no single cause. There are, however, certain risk factors for this disease:
- Ten percent of prostate cancer is inherited. These cancers usually develop at a younger age and are more aggressive (fast-growing). If one first-degree family member (father or brother) has prostate cancer, your risk for developing it is doubled. This risk increases to eleven-fold if three first-degree family members are affected.
- Ageing increases risk. The disease is exceedingly rare before the age of 40, but one in eight men between the ages of 60 and 80 suffer from it. Autopsy data indicate a 70% incidence of prostate cancer in 80-year-old men.
- A typical “Western” diet high in animal fats and red meat may increase risk.
There may be no symptoms at all in early prostate cancer. By the time the cancer becomes bothersome or apparent, it has usually spread so much it is no longer curable.
A tumour can cause lower urinary-tract symptoms similar to benign enlargement of the prostate (benign prostatic hyperplasia or BPH):
- Obstructive symptoms: poor stream, incomplete emptying and straining while passing urine.
- Irritative symptoms: frequent urination, urgency and nocturia (getting up to pass urine more than twice at night).
In advanced prostate cancer, the tumour cells can break loose and spread (metastasise):
- Bony metastases commonly involve the lower spine and pelvic girdle, causing lower backache and hip pain. If this is left untreated, it can lead to spinal fractures and paralysis.
- Lymphatic involvement can cause swelling of the legs and obstruction of the ureters (the tubes leading from the kidneys to the bladder), which can lead to renal failure.
Prostate cancer can also cause blood in the urine and ejaculate, but this is not common.
Early and asymptomatic prostate cancer can be diagnosed by routine cancer screening. (The same methods are used to diagnose patients with symptoms.) A tumour may also be discovered by chance during surgery for BPH.
Screening should be done yearly in men above the age of 50, or 45 if there is a family history of prostate cancer.
Your health professional will:
- Ask for a detailed medical history.
- Conduct a physical examination. A urine sample will probably be required. (Try not to empty your bladder shortly before the appointment.)
- Administer a PSA blood test. Prostate specific antigen (PSA) is a protein secreted by prostate cells. The normal PSA level in the bloodstream is below 4 nanograms per ml. If the PSA count rises above 4, it may indicate cancer. (However, in up to 20% of prostate cancers, the PSA is below 4. Other conditions, such as BPH, prostatitis (inflammation) or injury, may also raise PSA.)
- Perform a digital rectal exam (DRE). The prostate is clinically assessed by inserting a gloved finger into the rectum. The urologist palpates the prostate to get an impression of the size and consistency of the gland, and to detect possible cancerous nodules.
If there are suspicious nodules, or any abnormal findings with either the PSA or DRE, a biopsy of the prostate should be done. A tissue sample is taken with a needle. This procedure is performed under local or general anaesthesia, guided by ultrasound. It is normal to see blood in the urine, stool and ejaculate after this procedure, but this is temporary.
Staging and grading
Once a positive diagnosis has been made, the cancer will be staged and graded, which will determine how the disease should be managed:
- Staging refers to the extent and spread of the disease. Prostate cancer is staged with the TNM system. This classifies how much the cancer has grown in or beyond the prostate (T-stage), whether the lymph nodes are involved (N-stage), and whether the cancer has metastasised to other areas of the body (M-stage).
- Grading refers to what the cancer looks like under a microscope. The most commonly used system is the Gleason score (calculated out of 10), which rates how far the glandular pattern is distorted from a normal appearance. The higher the Gleason score, the more aggressive the tumour and the worse the prognosis.
Tests that may assist in grading and staging include spine, pelvis and chest X-rays and radionucleotide bone scans.
The choice of treatment depends on the stage of the cancer, as well as the condition of the specific patient – eg. their life expectancy, age and whether they have other diseases.
Cancers confined to the prostate, with no involvement of lymph nodes or other organs, are potentially curable by surgery or radiotherapy. After such treatment, the PSA should drop to undetectable levels. If not, or if PSA rises after an initial drop, it may indicate residual disease or metastases.
Patients with cancer that has grown beyond the capsule that encloses the prostate, or where there is lymph node involvement or metastatic spread, are not curable. However, hormonal treatment can limit the progression of the disease.
Finally, in certain cases the doctor and patient may decide to resort to “watchful waiting”: surveillance of the cancer, but no active treatment. PSA is monitored, and treatment begun only if a rise in PSA or tumour stage warrants it. This is suitable for some patients with very early low-risk cancers, and for those with less than 10 years of life expectancy, eg. very elderly men. (Due to the slow-growing nature of the disease, the benefits of a cure are usually only felt in 10 – 15 years.)
In a procedure called radical prostatectomy, the entire prostate and seminal vesicles are removed through incisions in the abdomen or perineum (between the scrotum and the anus). The pelvic lymph nodes may also be removed. The extracted prostate and nodes will be analysed to check if the cancer has been fully removed, and if lymph nodes are involved.
Surgery takes two to four hours. Afterwards, a catheter will stay in for 10-14 days and a wound drain for two days. Patients are usually discharged after about five days, and may be off work for four to six weeks.
The main complications after surgery are impotence and incontinence, although new surgical techniques have reduced these problems. The incidence of impotence is around 30% and incontinence about 4-10%. Erectile dysfunction can be treated with oral medication or penile injections at an early stage. Urinary incontinence usually improves in three to six months.
Radiation energy is used to kill the cancer cells. This can be delivered via external beam radiotherapy (EBRT) or brachytherapy. EBRT involves a few weeks of daily sessions.
Brachytherapy, done under general anaesthesia, involves implanting radioactive “seeds” into the prostate, with ultrasound guidance. The radiation is delivered only to the prostate, not to adjacent organs, limiting side-effects. Another advantage is that patients are discharged the same or next day after this relatively painless procedure, with few complications.
Prostate cancer is “fuelled” by the male hormone testosterone. Hormonal treatment deprives the tumour of testosterone. In 80% of patients, such treatment will cause shrinkage of metastases and a decline in PSA, improving symptoms. These effects can last for many years in some patients.
The two most common types of hormonal therapy are surgical and medical orchidectomy. Surgical orchidectomy is the surgical removal of the testes (castration), permanently stopping testosterone production. With medical orchidectomy, injections of drugs called LHRH analogues prevent the testes from producing testosterone. These can be given continuously on a three-monthly basis or intermittently, depending on the response of the cancer.
Side effects may include hot flushes (short-lived and transient), impotence and a decrease in sexual drive, osteoporosis and weight gain.
Avoiding a high intake of dietary fat and red meat may help prevent prostate cancer. Omega-3 fatty acid, contained in fish, is a healthy substitute. Tomato-containing products rich in lycopene are also beneficial, as well as anti-oxidants found in selenium and vitamins E and D.
Image via Thinkstock
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