Physicians will sometimes talk about a particular disease’s “natural history” or typical progression if it is left untreated indefinitely. With regard to prostate cancer, most cases of the disease are discovered while the cancer is still confined to the prostate itself.
This is called “local disease” or “localized disease.”
The disease is easiest to treat while it is confined to the prostate. At this stage, surgery and radiation are most likely to be curative and completely kill or remove whatever cancer cells are present. If left untreated, however, prostate cancer can proceed on a number of different paths.
It is well known that, sometimes, even when untreated, prostate cancer simply does not continue to grow or only grows at an extremely slow rate. This is not the case in the majority of men, but it does happen. In fact, some studies have shown that prostate cancer is present in the majority of older men at the time of their deaths even if they had not been diagnosed.
This suggests that many older men have prostate cancer that is small and slow-growing, but the disease causes them few symptoms and does not lead to their death.
Most cases of diagnosed prostate cancer, however, if left untreated, will grow and possibly spread outside of the prostate. The first sites of spread are typically to the nearby tissues.
Further advancement of cancer can occur when cancer cells enter the blood vessels and lymphatic channels and then spread to distant areas of the body. Once cancer has entered into these vessels, prostate cancer cells can “seed” into virtually any other part of the body. Prostate cancer is known to have a particular affinity for spreading or metastasizing to the bones especially the lower spine, pelvis, and femur. Other organs such as the liver, brain, or lungs can also be the sites of spread, but these are much more rare.
Once cancer has spread distantly from the prostate, it becomes far harder to effectively treat and completely cure. Chemotherapy and hormone therapy become the most feasible options because they treat cancer throughout the body.
If left to spread without intervention or, if treatment has failed, then prostate cancer can ultimately result in death.