Bone Scans for Prostate Cancer: Why and When

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Some men will need to undergo a bone scan to determine whether their prostate cancer has spread to the bones, particularly men with a Gleason score of 8-10 or who are in prognostic grade groups 4 and 5. (Prognostic grade groups are a new way to grade prostate cancer. Typically, the information is now reported in addition to the Gleason score.)

The bone scan involves intravenous injection of a small amount of a low-level radioactive substance that is preferentially taken up by damaged bone. (Bone can be damaged by cancer as well as by osteoporosis and other bone diseases.) A special scanner is then used to detect the radioactivity. Areas of the body that show increased radioactivity have bone damage, possibly because cancer has spread to the bone.

A bone scan is not typically ordered when PSA levels are less than 10 ng/mL because the likelihood of cancer spread is very low. Men who have a PSA level of 20 ng/mL or higher, a Gleason score of 8 to 10, or disease extensive enough to be felt on both sides of the prostate or beyond the prostate should have a bone scan and computed tomography (CT) or magnetic resonance imaging (MRI) of the pelvis to evaluate for enlarged lymph nodes.

New approaches for detecting the presence or progression of prostate cancer are being investigated. These include positron emission tomography (PET) and PET/CT using novel markers that bind to prostate cancer cells. Further development of these imaging procedures may provide more precise ways to diagnose recurrences and locate metastases (cancers that have spread).

After gathering this information, the physician can then describe the clinical stage (or extent) of the cancer. Clinical stage takes into account whether the cancer has spread to the lymph nodes, bones, or other areas.