High-risk prostate cancer: Why and when a bone scan may be necessary

At some point during prostate cancer treatment, a bone scan may be necessary. For men with low- and intermediate-risk prostate cancer, a bone scan is generally not needed.  For these men, a bone scan is unlikely to provide any additional information the doctor will need as prostate cancer does not spread to the bones until it reaches a more advanced stage. Men with high-risk prostate cancer, however, do need a bone scan in order to look if their cancer has spread to the bones.  

What is a bone scan?

A bone scan is an imaging test that may be used to detect cancerous cells, evaluate fractures in bones or to monitor bone conditions such as infections and arthritis. During a bone scan, a small dose of radioactive material is injected into a vein, where it travels through the bloodstream.  The material collects in the bones and is detected by a scanner using nuclear imaging to reveal cell activity and function in the bones.

A bone scan may detect cancer that has metastasized to the bone from a different primary site, such as the breast, prostate, or lungs. It may also be used to evaluate bone health before treatement.

How is it determined which men should have a bone scan?

Prostate cancer can metastasize or spread to a man’s bones when it reaches an advanced stage such as high-risk prostate cancer. A man with high-risk prostate cancer may not necessarily know himself if this has occurred but some men who are experiencing bone pain or have a blood test showing elevated calcium levels, may be indicators of prostate cancer that has metastasized to the bones.

Men with a Gleason score of 8-10 or who are in prognostic grade groups 4 and 5, is another way to tell if a man should have a bone scan.

Typically, a bone scan is not ordered when a man’s prostate specific antigen (PSA) level is less than 10 ng/dl because the likelihood of cancer spread is very low. Men who have a PSA level of 20 ng/dl 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.

Other methods for detecting metastasized prostate cancer

Besides a bone scan, there are several other ways to help a doctor determine if a man’s prostate cancer has metastasized. A common imaging workup may include a CT scan of the abdomen and pelvis.  Prostate cancer that has spread to the live, intestines, or bones of the abdomen and pelvis can usually be found with a CT scan. Cancer, which has spread to the lymph nodes, can sometimes be found if the lymph nodes have become enlarged.

MRI’s are sometimes used if there is a question as to whether the cancer has spread into tissues near the prostate or to see if there is tissue left behind in the prostate area following surgery.

A positron emission tomography (PET) scan is an imaging test that looks at a person’s body function as well as it anatomy. PET scans are often combined with a CT scan. For this procedure, a man will be injected with a small amount of radioactive sugar. Cells which are actively growing, such as cancer cells, take the sugar and light up during the exam, indicating where the cancer is located. In some cases and with some cancers, PET scans can assist with staging your cancer in ways other tests cannot.

Bottom line

Bone scans for advanced prostate cancer is an important tool for detecting and determining if prostate cancer has spread beyond the prostate gland.  Always discuss with your doctor any concerns or questions you have in regards to this procedure.