The tumor stage refers to the size and the extent of cancer (how much is present). A staging system exists that quantifies the extent or volume of disease. When the cancer is low volume and confined to a small area of the prostate, treatment outcomes are improved compared to those situations where prostate cancer involves a significant portion of the prostate gland.

Furthermore, those cancers confined to the prostate can be more successfully treated than those that have spread beyond the prostate. Cancers that have spread beyond the prostate to the lymph nodes or bone have less favorable outcomes with treatment.