The Facts on Prostate Cancer
Prostate cancer is the cancer most often diagnosed in Canadian men. In 1999 in Canada, 16,600 men were diagnosed with the disease.
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, called a tumour.
In some people, the genetic mutation is inherited. About 10 % of prostate cancers occur in people who have particular genetic mutations. However, 90% of 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) coming from outside the cell. People of African descent have double the prostate cancer rates of Caucasians, probably 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 – more than 80% of prostate cancers are found in men over 65
family history – having a father or brother with prostate cancer doubles your risk
race – people of African descent are more likely to get prostate cancer
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 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-fat diets and prostate cancer. Some experts contend that lack of fruit and vegetables is the problem, and that people with high-fat diets get more cancer because they tend to eat fewer vegetables. As well as fat, high levels of dietary calcium, as in dairy products, have been linked to prostate cancer.
Some foods may protect against prostate cancer. Tomatoes, grapefruit, and watermelon all contain lycopene, a chemical that’s clearly linked to a lower risk of prostate cancer. Many studies have also found a protective effect in vitamin E.
Symptoms and Complications
Usually prostate tumours are 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 or making urination difficult or painful. They may also interfere with the nerves responsible for erection of the penis, causing impotence. Advanced tumours can also press on the spine or pelvis, causing pain. Pain or burning when urinating or pain when ejaculating may also occur. Blood may appear in the urine or semen. Pain or stiffness in the lower back, hips, or upper thighs may also occur.
If cells from a tumour are shed 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, 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 in the lungs, brain, bones, lymph nodes, or almost anywhere else.
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.
Another test a doctor can do is a digital rectal exam (DRE), which involves feeling the prostate with a gloved finger. If cancer is suspected, a needle biopsy might be done next, which involves removing cells from the prostate with a syringe. The doctor will also want a biopsy sample of the lymph nodes to check if the disease has spread.
If cancer is found, a specialist, usually a urologist, will then determine the size, stage, and grade of the tumour. These will help sort out which therapy may be used to treat the cancer.
Treatment and Prevention
Prostate tumours grow slowly 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, and are followed by “watchful waiting.” The doctor will check regularly to be sure the cancer isn’t growing faster than expected.
Cancer that has spread far beyond the prostate requires a range of anti-tumour and pain-killing treatments.
Cancer that is still localized in the prostate is usually treated with surgery. 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. The 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. Sometimes the doctor tries to leave them in place but impotence occurs anyway. The doctor should be consulted about the likelihood of a “nerve-sparing” procedure in any specific case.
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 for radical prostatectomy.
Radiation may be used to kill the cancerous tissue. This also carries a large risk of impotence and incontinence, though newer machines are better at focusing the harmful rays on cancer tissue only. Sometimes radioactive pellets are placed into the prostate gland.
Hormonal therapy involves reducing the levels of the male hormones like testosterone (called androgens). 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 may be useful before surgery, especially cryosurgery. Both hormones and radiation are common treatments in patients whose cancer has spread or come back after surgery. Normal cancer chemotherapy is not commonly used for prostate cancer, except to relieve symptoms from metastases.
The doctor will discuss treatment options based on the size, type, and location of the cancer.
If you’re worried about developing prostate cancer and have more than one of the risk factors listed in the causes section, you should ask your doctor about PSA testing and digital rectal exams.