Prostate cancer is the most often diagnosed cancer in Canadian men, aside from skin cancers. It ranks third as a cause of cancer death in Canadian men aged 65 and over.
As an important part of the male reproductive system, the walnut-shaped prostate gland produces liquid that moves sperm. It is located between the rectum and the pubic bone, beneath the bladder.
When the condition is found early, and if it is located only in the prostate gland, treatment of prostate cancer can be more successful. If the cancer spreads to other areas of the body, treatment may become more difficult.
Cancer tumours grow from cells that have undergone genetic mutations. These changes cause cells to multiply at very fast rates. They eventually form a mass that keeps growing – this is called a tumour.
In some people, the genetic mutation is inherited. Some prostate cancers occur in men who have particular genetic mutations, such as genetic mutations seen in some families with breast and ovarian cancer. However, most cancer-causing genetic changes occur after birth.
Some genes don't directly cause cancer, but may make cells more vulnerable to carcinogens (cancer-causing agents) found outside the cell. Men of African descent have almost double the prostate cancer rates of Caucasians, possibly due to this factor.
Various factors can increase or reduce the chance of mutations, and therefore cancer. The following factors are believed to increase the risk of prostate cancer:
- age: Greater age, especially over 65, comes with greater risk.
- family history: Having a father or brother with prostate cancer doubles your risk (some families carry gene mutations that increase the risk of developing prostate cancer).
- race: Men of African descent are more likely to get prostate cancer and men of East Asian descent are at a lower risk.
- geography: Prostate cancer is rarer in Asia, Africa, and South America.
- weight, physical inactivity: Overweight and inactive men have higher rates of prostate cancer.
- diet: Eating high-fat foods and red meats, and not eating enough vegetables, fruits, and fibre increases your risk.
- smoking: People who smoke have a higher risk of developing prostate cancer and a poorer prognosis after diagnosis.
Diet may be a crucial factor in prostate cancer. The fact that Africans are far less affected by prostate cancer than Americans of African descent suggests that diet and lifestyle are partly to blame. Research has shown a link between high saturated-fat diets and prostate cancer. Some experts argue that a lack of fruits and vegetables is the problem, and that people with high-fat diets get more cancer because they tend not to eat enough vegetables. Along with a high-fat diet, very high calcium intake has also been linked to prostate cancer.
Some foods may protect against prostate cancer. Tomatoes, grapefruit, and watermelon all contain lycopene, a chemical that may lower risk of prostate cancer. Many studies have also suggested a protective effect for vitamins E, selenium, and cruciferous vegetables like broccoli, cauliflower, Brussels sprouts, and bok choy. If you plan on supplementing your diet with any of these nutrients, be sure to talk with your doctor or pharmacist first. For example, high doses of zinc supplements (more than 100 mg daily) may lead to an increased risk of developing the condition.
Symptoms and Complications
Prostate tumours are usually small and cause no symptoms. That's why most of them are only discovered during blood screening tests or surgery for benign prostatic hyperplasia, which often does cause noticeable symptoms.
Large, advanced tumours can press on other organs such as the bladder, causing incontinence (reduced bladder control) or making urination difficult or painful. Problems related to urination may occur as a result of prostate cancer because the urethra (the tube that carries urine from the bladder out of the body) passes directly through the prostate gland. These tumours may also interfere with the nerves responsible for erection of the penis, which leads to erectile dysfunction.
Advanced tumours can also cause:
- pain by pressing on the spine or pelvis
- burning or pain when urinating
- frequent urination
- pain when ejaculating
- blood to appear in the urine or semen
- pain or stiffness in the lower back, hips, or upper thighs
If cells from a tumour break off and move into the bloodstream, they can settle in distant parts of the body and start dividing to form new tumours. This process of migration is called metastasis, and the new tumours are called metastases. You may suffer pain in distant parts of the body if the cancer has metastasized.
As well as travelling by blood, loose cancerous cells can be carried through the lymphatic system, which is a network of tubes that carry lymph (a clear liquid containing waste products and immune cells). From there, it can spread to various lymph nodes and other organs. The lymphatic system is the main carrier of metastases in prostate cancer. Secondary tumours can grow almost anywhere in the body, such as the lungs, brain, lymph nodes, however, it is most likely to spread to the bone.
Making the Diagnosis
There is a screening test for prostate cancer called the prostate-specific antigen (PSA) test. PSA is made by prostate cells and all men have PSA levels that can be detected in the blood. Men with prostate cancer often have more PSA. High PSA levels can also occur with noncancerous conditions, and PSA may be low in people with prostate cancer. Therefore, repeat testing may be done to confirm the results. If high PSA levels are found repeatedly, doctors may suggest taking a biopsy. As people age, PSA test may become less reliable in identifying prostate cancer. You should discuss with your doctor about whether you require PSA testing.
Another test a doctor can do is a digital rectal exam (DRE), which involves feeling the prostate with a gloved finger. If there is a high PSA level, or a lump is felt, small tissue samples will be taken from about 8 to 12 locations in the prostate with the use of a biopsy gun. The doctor guides the biopsy gun with the aid of a transrectal ultrasound (TRUS), a device that creates an image of the prostate. The doctor will also want a biopsy sample of the lymph nodes to check if the disease has spread. You may have short periods of sharp pain during this procedure. Sometimes, doctors will freeze the area to help reduce the pain.
If cancer is found, a specialist (usually a urologist) will determine the size, stage, and grade of the tumour. This information will help determine which therapy may be used to treat the cancer.
Treatment and Prevention
Prostate tumours grow slowly, often over a period of 10 years or more and are non-aggressive compared to most other types of cancer. They also tend to appear late in life. Especially in older men, small tumours are often left in place without any treatment. However, the doctor will check regularly to be sure the cancer isn't growing faster than expected. This is known as "active surveillance."
Cancer that has spread far beyond the prostate requires a range of antitumour and pain-killing treatments.
Cancer that hasn't spread beyond the prostate is usually treated with surgery or radiation.
One option for treatment is radiation therapy. Your doctor may use an external beam or radioactive seed implants inserted into or near the prostate through surgery (called brachytherapy) to destroy cancer cells. Researchers are looking for new ways to deliver radiation therapy, as well as the potential use of hormone therapy at the same time as radiation therapy (see the information below about hormone therapy).
If surgery is recommended, the standard operation is radical prostatectomy, the complete removal of the prostate gland. An incision is made either in the lower abdomen or between the anus and scrotum, and the prostate gland is removed. This is the method most likely to cure prostate cancer.
Removal of the prostate can have major side effects, including impotence and incontinence. A man's ability to have an erection after surgery depends on whether the nerves next to the prostate have been damaged. Sometimes, the nerves are affected by cancer and must be removed. Other times, the doctor tries to leave them in place but impotence occurs anyway. Your doctor should be consulted about the likelihood of a "nerve-sparing" procedure in any specific case.
When deciding on whether surgery or radiation is the best choice to treat prostate cancer, both the doctor and patient need to discuss the risks and benefits. Both forms of treatment have complications, such as bladder irritation, sexual dysfunction, and bowel symptoms, and the decision will depend upon the disease extent, general health, and preferences of the individual patient.
Sometimes the cancerous tissue is killed with a cold probe (cryosurgery) that freezes it. This technique can also cause impotence. It's fairly new, so we don't know if long-term results are as good as those of radical prostatectomy.
Hormonal therapy involves reducing the levels of the hormones like testosterone (called androgens) or blocking the cancer cells from detecting those hormones. Prostate cancer cells rely on androgens to grow. This treatment can also cause the prostate to shrink. It won't cure the cancer, but it can control the growth of the tumour and may be useful before surgery, especially cryosurgery. Instead of using medications, some men may choose to reduce their levels of testosterone by having their testicles removed (orchiectomy).
Both hormones and radiation are common treatments in patients whose cancer has spread or come back after surgery. Chemotherapy can be used for prostate cancer when hormonal therapy is no longer working.
Your doctor will discuss treatment options based on the size, type, and location of the cancer.
If you are worried about developing prostate cancer, you should ask your doctor about PSA testing and digital rectal exams.
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