Stage 4 prostate cancer is the most advanced stage of the disease. It means that the cancer has spread beyond the prostate to distant areas of the body.
It is also known as stage T4 (using the TNM staging system).
Specifically, stage 4 prostate cancer means that the tumor has spread beyond the prostate to other structures or tissues, even distant ones. The bones are a favored site of prostate cancer spread.
Kumar V, Abbas A, Fausto N. Robbins Pathologic Basis of Disease 7th Edition. 2004.