Natural History of Prostate Cancer if Left Untreated

While most men undergo some form of treatment for their prostate cancer, some men today choose to not be treated for their prostate cancer. Instead, they may choose to have their doctors monitor their cancer, especially if it's expected to grow slowly based on biopsy results, confined to the prostate, not causing any symptoms, and/or small. This is called active surveillance, meaning doctors will initiate cancer treatment only if cancer starts growing.

Others choose no cancer treatment because of a short life expectancy or other serious medical problems. They may feel that the risks or side effects of cancer treatment (like surgery and radiation) outweigh their potential benefits. This option is certainly OK and reasonable in the right circumstances—requiring a careful and thoughtful discussion with your doctor and family.

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.

If left untreated, most cases of diagnosed prostate cancer will grow and possibly spread outside of the prostate to local tissues or distantly to other sites in the body. The first sites of spread are typically to the nearby tissues. The cancer can spread down the blood vessels, lymphatic channels, or nerves that enter and exit the prostate, or cancer could erode directly through the capsule that surrounds the prostate. The seminal vesicles are a site of particularly common early spread. More extensive “local” spread can occur with cancer invading the nearby bladder or rectum.

Further advancement of cancer can occur when cancer cells enter the blood vessels and lymphatic channels. 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 rarer.

It's important to know (and it's fairly well known) that, sometimes, even when untreated, prostate cancer simply does not continue to grow or only grows at an extremely slow rate. 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.

A Word From Verywell

Prostate cancer is a complicated disease and requires extremely careful thought when determining the best treatment option (for yourself or your loved one). There are a number of available therapies and not necessarily a single best fit—so seek the guidance of your doctor, and don't be afraid to get a second opinion.