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.
Initially the cancer cells are 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.
Adenocarcinoma: the most common type of prostate cancer
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 atypical 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 tumor has become large enough to penetrate outside the capsule. The behavior or personality of any particular prostatic adenocarcinoma is locked up in the genetic code of its mutant cells.
How common is prostate cancer?
Prostate cancer has become the most common cancer affecting North American men, accounting for 28% of all newly diagnosed cancers: 317,000 in the USA and 20,000 in Canada (1997 estimate). In 1996 it caused 13% of male cancer-related deaths: 42,000 in the USA and 4,000 in Canada. In essence, a new case of prostate cancer is diagnosed every two minutes in North America and another man dies of it every 12 minutes - 120 deaths per day.
The increased incidence during the past two 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