Prostate cancer is the cancer most often diagnosed in Canadian men. It is second only to lung cancer as a cause of cancer death in Canadian men aged 65 years and over. Every year, about 20,000 Canadian men are diagnosed with prostate cancer.
The walnut-shaped prostate gland is an important part of the male reproductive system: it produces liquid that moves sperm. It is located between the rectum and the pubic bone.
Causes and risk factors
Cancer tumours grow from cells that have undergone genetic mutations. In some people, the genetic mutation is inherited. 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.
The following factors are believed to increase the risk of prostate cancer:
- age - especially over 65
- family history - having a father or brother who has or has had prostate cancer doubles your risk
- 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 and South America
- weight and physical inactivity - overweight and inactive men tend to have higher rates of prostate cancer, but the exact link between being overweight or inactive and prostate cancer is not clear
- diet - saturated fats and a lack of fruit and vegetables can increase the risk; tomatoes, grapefruit, and watermelon contain lycopene, a chemical that may lower prostate cancer risk
Usually prostate tumours are small and cause no symptoms. It is a slow growing cancer so men might not experience symptoms, especially in the early stages. That's why most of them are only discovered during blood screening tests or surgery for benign prostatic hyperplasia, a condition which often does cause noticeable symptoms. Occasionally, digital rectal exams (DRE) performed by a doctor will indicate a need for further tests.
Large, advanced tumours can press on other organs such as the bladder, causing:
- incontinence (reduced bladder control)
- difficult urination (peeing)
- burning or pain when urinating
- erectile dysfunction
- pain when ejaculating
- blood 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 is called metastasis, and the new tumours are called metastases. You may experience pain in distant parts of the body if the cancer has metastasized.
Loose cancerous cells can also 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 lymph nodes and other organs. The lymphatic system is the main carrier of metastases in prostate cancer. Prostate cancer can spread to the lungs, brain, bones, lymph nodes, or almost anywhere else.