Prostate cancer does not develop overnight. It can take years of cells dividing before a normal cell becomes a cancerous cell. The cell first undergoes very small changes in which it becomes slightly abnormal or atypical, as seen under a microscope. It may also begin to divide, grow more quickly, and develop some abnormal characteristics (dysplasia). Then, over the years the cells and glandular structures continue to change, become more abnormal-looking, and finally cancerous.
Cancer cells are initially confined within the prostate ducts and glands (in situ cancer), but with time the cells develop the ability to invade out of the ducts and into the blood and lymphatic system (an invasive cancer).
Unfortunately, it is not possible to detect one or a few abnormal cancer cells. At present, technology is only capable of detecting a small lump or mass of cancer cells that may have been growing slowly for several years. By the time a cancer can be detected as a lump, it contains roughly one billion cells.
By far the most common type of prostate cancer is that which originates within the tiny glands of the prostate itself. This type of glandular cancer is called an adenocarcinoma. Many cases are detected by a careful digital rectal examination of the gland during a routine medical examination.
As with all other types of cancer, an adenocarcinoma starts as a single mutant cell that grows and multiplies to involve increasing amounts of the prostate. If left untreated, the cancer cells will eventually go through the capsule of the gland and find their way into lymph nodes, bones, or other tissues. This may occur early on in the growth of this cancer, or it may take many years to occur. Sometimes, cancer cells may escape from the prostate into blood or lymph vessels even before the tumour has become large enough to penetrate outside the capsule. The behaviour or personality of any particular prostatic adenocarcinoma is locked up in the genetic code of its mutant cells.
Prostate cancer has become the most common cancer affecting North American men, accounting for 28% of all newly diagnosed cancers: 192,000 in the USA and 25,500 in Canada (2009 estimate). In 2009 it is estimated to cause 27.360 deaths in the USA and 4,400 in Canada.
The increased incidence during the past 2 decades is due to several factors. First, men are now living longer so they are at risk of getting prostate cancer, or any other disease, over a longer period of time. Second, because physicians now have a better understanding of prostate cancer they are performing more rectal examinations and are using diagnostic tools such as PSA and transrectal ultrasound more often to detect the cancer early.
Therefore, part of the apparent increase in prostate cancer is due to the fact that it is simply being diagnosed more often instead of going undetected. However, there are likely other, as yet undefined, reasons contributing to the increasing number of cases.
Excerpt from the Intelligent Patient Guide to Prostate Cancer by S. Larry Goldenberg, MD
in association with the MediResource Clinical Team
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