Prostate Cancer

Introduction

As the name suggests, prostate cancer develops from cells of the prostate gland. The prostate gland is about the size of a walnut and is located in front of the rectum, behind the base of the penis, under the bladder. It is found only in men, and produces same of the seminal fluid, which protects and nourishes sperm cells.

The prostate surrounds the upper part of the urethra, the tube that carries urine and semen out of the penis. Nerves located next to the prostate take part in causing an erection of the penis.

When a person is affected by prostate cancer, the cancer cells may spread outside the gland to other parts of the body. Most prostate cancers grow very slowly and never cause symptoms or spread. Autopsy studies show that many elderly men who died of other disease also had a prostate cancer which neither they nor their doctor were aware of. But some prostate cancers can grow and spread quickly. The people most likely to get prostate cancer are men over age 50.

Prostate cancer is the second leading cause of cancer death in men, exceeded only by lung cancer. It accounts for about 13 per cent of male cancer-related deaths. The cause of prostate cancer is not known.

In the early stagers of prostate cancer usually there are no symptoms. Most prostate cancers are discovered during a routine rectal examination. In the later stages urinary obstruction may be observed accompanied by pain in the low back or pelvis from spread of cancer.

Eighty-nine percent of men diagnosed with prostate cancer survive at least 5 years, and 63 per cent survive at least 10 years. Fifty-eight per cent of all prostate cancers are found while they are still confirmed to the prostate.

Thirty-one per cent of prostate cancers have already spread locally (to tissues near the prostate) at the time of diagnosis.

Treatments that remove or damage nerves located next to the prostate nerves can cause erectile dysfunction, also known as impotence. Although early diagnosis and treatment of prostate cancer may help some men to live longer, it has no impact on the life span of other men.

Prevention and risk factors

Although some factors increase a person's risk of getting cancer, they do not always cause the disease. Many people with one or more risk factors never develop cancer, while others with this disease have no known risk factors.

While the causes of prostate cancer are not yet completely understood, researchers have found several factors that are consistently associated with an increased risk of developing this disease. Prostate cancer seems to run in some families, suggesting an inherited or genetic factor. Having a father or brother with prostate cancer usually doubles a man's risk of developing this disease. The risk is even higher for men with several affected relatives, particularly if they were young at the time of diagnosis.

The chance of having prostate cancer increases rapidly after age 50. More than 80 per cent of all prostate cancers are diagnosed in men over the age of 65.

Some studies suggest that men who eat a lot of fat have a greater chance of developing prostate cancer. Other research indicates that men with a high-fat diet ten to cat fewer fruits and vegetables and more dairy products, and that these factors may be responsible for increasing risk rather than the amount of fat itself. Lycopenes, which are found in especially high levels in some fruits and vegetables (such as cooked or raw tomatoes and watermelon) also seem to lower prostate cancer risk. These vitamin-like substances are antioxidants that help prevent damage to DNA and may help lower prostate cancer risk. The mineral selenium also seems to lower the risk of prostate cancer.

Recent research also suggests that a diet high in calcium and low in fructose (fruit sugar) increases the risk of prostate cancer.

Regular physical activity and maintaining a healthy weight may help reduce prostate cancer risk.

Men who have had a vasectomy may have an increased risk for prostate cancer. Some studies have found that prostate cancer develops one to two times more often in these men, but other studies found no difference in prostate cancer risk. Some studies that noticed an increase in risk found that this risk is highest in men who were younger than 35 when they has a vasectomy.

The role of vitamin supplements in reducing prostate cancer risk is not entirely certain, but some studies suggest that taking 50 mg of vitamin E daily can lower risk by 32 per cent. Although other studies found vitamin E to be of no benefit, reasonable doses of this vitamin have no significant side effects.

Some other studies suggest that taking vitamin A supplements may actually increase prostate cancer risk. As always, vitamin supplements should be used with the consent of a doctor.

What causes prostate cancer

What causes prostate cancer is still not known exactly but, researchers have found some risk factors and are making progress toward understanding how these factors cause cells in the prostate gland to become cancerous.

During the past few years, scientists have made great progress in understanding how certain changes in DNA can cause normal prostate cells to grow abnormally and form cancers. DNA is the chemical that carries the instructions for nearly everything our cells do. We usually resemble our parents because they are the source of our DNA. However, DNA affects more than our outward appearance. Some genes (parts of our DNA) contain instructions for controlling when cells grow and divide.

Certain genes that promote cell division are called oncogenes. Others that slow down cell division or cause cells to die at the appropriate time are called tumour suppressor genes. It is known that cancers can be caused by DNA mutations (defects) that turn on oncogenes or turn off tumour suppressor genes. Some people with certain types of cancer have DNA mutations they inherited from a parent. Researchers have recently found that inherited DNA changes in certain genes make them more likely to develop prostate cancer. These genetic changes appear to be responsible for about 10 per of prostate cancers.

DNA mutations related to prostate caner usually develop during a man's life rather than having been inherited before birth.

There is evidence that development of prostate cancer is linked to increased levels of certain hormones. High levels of androgens (male hormones) may contribute to prostate cancer risk in some men. Researchers have recently noted that men with high levels of another hormone, insulin-like growth factor-1 (IGF1), are more likely to develop prostate cancer.

Detection and symptoms

Some prostate cancers may be found because of symptoms such as slowing or weakening of the urinary stream or the need to urinate more often. These symptoms, however, can also be caused by benign diseases of the prostate. Symptoms of advanced prostate cancer include blood in the urine, impotence, and pain in the pelvis, spine, hips, or ribs. These symptoms, again, may also be present with other diseases.

SOME TESTS FOR PROSTATE CANCER

Prostate-specific antigen blood test

This blood test to measure PSA - a protein which is made by prostate cells - is recommended annually to men over 50 and to younger men with high prostate cancer risk.

PSA blood test results are reported as nanograms per milliliter (ng/ml). Results under 4 ng/ml are usually considered normal. Results over 10 ng/ml are high and values between 4 and 10 are considered borderline. The higher the PSA level, the more likely the presence of prostate cancer.

PSA levels estimate how likely a man is to have prostate cancer but conditions such as benign prostate hyperplasia (non-cancerous prostate enlargement) can cause a borderline or high PSA result. ON the other hand, some men with prostate cancer have negative or borderline PSA results. Several medications and herbal preparations can also lower blood PSA levels. Men with a high PSA result are advised to have a biopsy, to find out whether or not cancer is present.

After surgery or radiation treatment, rising PSA levels can provide an early sign that the cancer is coming back. Digital rectal examination

The doctor inserts a gloved, lubricated finger into the patient's rectum to feel for any irregular or abnormally firm area that might be a cancer. This is called a digital rectum examination (DRE).

The prostate gland is located next to the rectum, and most cancers begin in the part of the gland that can be reached by a rectal exam. The exam causes no pain and only takes a short time.

If the DRE result is abnormal, a biopsy is recommended regardless of the PSA levels. DRE is less effective than the PSA blood test in finding prostate cancer but can sometimes and cancers in men with normal PSA levels. The DRE is also used once a man is known to have prostate cancer, in order to help predict whether the cancer has spread beyond his prostate gland. It is also used to detect cancer that has come back after treatment.

Transrectal ultrasound

Transrectal ultrasound (TRUS) uses sound waves to create an image of the prostate on a computer screen. Sound waves are released from a small probe placed in the patient's rectum. The sound waves create echoes as they enter the prostate. The same rectal probe detects the echoes that bounce back from the prostate and a computer translates the pattern of echoes into a picture.

Because prostate tumours and normal prostate tissue often reflect sound waves differently, this test may be useful in detecting tumours, even those which might be too small or located in areas of the gland that cannot be felt by DE. The procedure is essentially painless and takes about 10-20 minutes.

TRUS is useful when the PSA or DRE indicates an abnormality, to guide the biopsy needle into exactly the right area of the prostate.

The prostate biopsy

A biopsy is a surgical procedure that removes a sample of tissue for examination. A core needle biopsy is the main method used to diagnose prostate cancer. Under transcrectal ultrasound guidance a doctor inserts a narrow needle through the wall of the rectum into the area of the prostate gland that appears abnormal. The needle then removes a cylinder of tissue, which is then tested. The procedure takes about half an hour and causes little discomfort.

When prostate cancer is affirmed

If cancer is found in a prostate biopsy, it is graded in order to estimate how fast it is likely to grow and spread. Prostate cancers are graded according to how closely they look like normal prostate tissue.

The most commonly used prostate cancer grading system is called the Gleason system. This system assigns a Gleason grade ranging from 1 through 5 based on how much the arrangement of the cancer cells mimics the way normal prostate cells from glands. If the cancer cell clusters resemble the small, regular, evenly spaced glands of normal prostate tissue, a grade of 1 is assigned. If the cancer lacks these features and its cells seem to spread haphazardly through the prostate, it is a grade 5 tumour.

Cancers with a high Gleason score are more likely to have already spread beyond the prostate gland at the time they are detected. Therefore, the Gleason score along with the blood PSA level and DRE is useful in considering treatment options.

Staging prostate cancer

If the prostate biopsy finds a cancer, more tests are done to find out how far the cancer has spread. This is called staging. The stage of a cancer is the most important factor in choosing treatment options. Physical examination

The physical exam, especially the digital rectal examination, is an important part of prostate cancer staging. The DRE can tell whether the cancer is limited to one side of the prostate, whether it has spread to the other side as well, or if it has spread beyond the prostate gland.

Imaging tests used for prostate cancer staging

Computed tomography

Commonly known as a CT or CAT scan, this test uses an x-ray beam to create a series of pictures of your body from any angles. A computer combines the information from all these pictures to produce a detailed cross-sectional image. This may reveal abnormally enlarged lymph nodes. Lymph nodes are a network of bean-sized collections of white blood cells that fight infection. Some prostate cancers spread to nearby lymph nodes, called pelvic lymph nodes. Enlarged pelvic lymph nodes could be a sign of spreading cancer, or could mean that your body is fighting an infection.

Magnetic resonance imaging (MRI)

MRI uses magnetic fields to create detailed cross-sectional pictures of selected areas of your body. These pictures can show abnormal areas of bones or lymph nodes that suggest cancer may have spread from the prostate.

Radionuclide bone scan

This procedure helps show whether the cancer has spread from the prostate gland to bones. The patient receives an injection of radioactive material. This low level of radiation does not cause any side effects. The radioactive substance is attracted to diseased bone cells throughout the entire skeleton. Areas of diseased bone will be seen on the bone scan image as dense, gray areas, called 'hot spots'.

Lymph node biopsy

This procedure is done to find out if cancer has spread from the prostate to nearby lymph nodes. Lymph nodes may be removed by the surgeon through an incision in the lower part of the abdomen and test them for cancer. Another way is to take a sample of cells from a lymph node by using fine needle aspiration (FNA), in which CT scan images guide a long, thin needle into the lymph nodes. The syringe attached to the needle takes a small tissue sample from one of the lymph nodes. There is no incision, no scar, and the patient can return home a few hours after the procedure.

A surgeon may also use a laparoscope, which is a long, slender tube inserted into the abdomen through a very small incision. The laparoscope allows the surgeon to view lymph nodes near the prostate and remove these pelvic lymph nodes using special surgical instruments operated through the laparoscope.

The TNM staging system

While there are several different staging systems for prostate cancer, the most commonly used system is the TNM system. It describes the extent of the primary tumour (T stage), the absence of spread to nearby lymph nodes (N stage), and the absence or presence of distant metastasis (M stage).

Side effects of prostate cancer treatments

Incontinence

Incontinence is the inability to control the urine stream, resulting in leakage or dribbling of urine. The patient may have urine leakage when coughing, laughing, sneezing, or exercising. Treatment of incontinence depends on its type, cause, and severity. Options include exercises to strengthen bladder muscles, biofeedback, medications, and additional surgery.

Normal bladder control returns for many patients within several weeks or months after radical prostatectomy. Mild stress incontinence may persist permanently after surgery in up to 35 per cent of men.

Impotence

Impotence, also known as erectile dysfunction, is an inability to get an erection of the penis. The nerves that allow men to get erections may be damaged or removed by radical prostatectomy. Radiation therapy and cryosurgery can also cause damage to these nerves. However, during the first 3 to 12 months after radical prostatectomy, most men will not be able to get a spontaneous erection.

Side effects of cryosurgery

Freezing can damage nerves near the prostate and cause impotence and incontinence. These complications occur about as often after cryosurgery as they do after radical prostatectomy. In addition, freezing may damage the bladder and intestines, leading to pain, a burning sensation, and the need to empty the bladder and bowels often. About 50 per cent of men notice swelling of their penis and scrotum after cryosurgery, usually lasting a couple of weeks.

Side effects of radiation therapy

These may include diarrhoea with or without blood in the stool, and an irritated large intestine. Occasionally, normal bowel function does not return after treatment is stopped. Both during and after treatment, other side effects may include frequent urination, burning sensation while urinating and blood in the urine. Radiation therapy may also cause a feeling of fatigue that may not disappear until a month or two after treatment stops. Impotence usually does not occur right after radiation therapy but gradually develops over one or more years. Side effects of chemotherapy

The side effects of chemotherapy depend on the type of drugs, the amount taken, and the length of treatment. Temporary side effects might include nausea and vomiting, loss of appetite, loss of hair, and mouth sores. Because chemotherapy can damage the blood-producing cells of the bone marrow, patients may have low blood cell counts. This can result in an increased change of infection. Most side effects, however, disappear once treatment is stopped.

Side effects of hormone therapy

  • Hot flashes similar to those experienced by women in menopause, sometimes controllable with other drugs such as Megace.
  • Breast enlargement, which may be prevented by treatment with radiation to the breasts prior to the start of the hormone blockade treatments.
  • Impotence-varying degrees are experienced. Generally, potency returns hormone therapy is discontinued. Actually, loss of libido is experienced more often than impotency.
  • Other possible side effects include, anaemia, weight gain, loss of muscle mass, loss of body hair, and diarrhoea.