PET Scan for Prostate Cancer

The acronym "PET" stands for positron emission tomography

Man Receiving Medical Scan for Prostate Cancer Diagnosis
Mark Kostich/E+/Getty Images

The PET scan for prostate cancer can sometimes be used to determine if prostate cancer has spread to other sites in the body and, if so, where.

What is Prostate Cancer?

Prostate cancer develops in the prostate — a small gland that makes seminal fluid. It is one of the most common types of cancer in men. Prostate cancer usually grows over time and in the beginning usually stays within the prostate gland, where it may not cause serious harm.

While some types of prostate cancer grow slowly and may need minimal or no treatment, other types are aggressive and can spread quickly.

Symptoms of Prostate Cancer

Prostate cancer that is more advanced may cause signs and symptoms such as:

  • Difficulty urinating
  • Decreased force in the stream of urine
  • Blood in the semen
  • Discomfort in the pelvic area
  • Bone pain
  • Erectile dysfunction

What Is a PET Scan?

The acronym "PET" stands for positron emission tomography. For our purposes, it doesn't really matter what that means beyond the fact that tiny amounts of radioactivity (which is injected into the body) is detected outside of the body by a large machine commonly known as the "PET scanner".

A PET scan involves the injection of a form of radioactively tagged glucose (a sugar that the body naturally metabolizes or uses). Tissues in the body that use up a lot of glucose will also use up a lot of the special radioactively tagged glucose used for the PET.

Those tissues will then be marked with radioactivity that can be detected by the PET scanner.

Lots of normal tissues rapidly use glucose (such as the heart, liver, spleen, and kidneys). What makes the PET scan useful, however, is that cancer cells typically also use a lot of glucose because they are dividing and multiplying at a much higher rate than normal cells.

By detecting abnormal sites of high glucose use on the PET, doctors can determine where there may be additional areas of cancer scattered throughout the body. This can help in choosing the most appropriate treatment.

Additionally, at many hospitals, PET is now combined with a CT scan to make a precise determination of exactly where cancer has spread much easier.

Why Isn't PET Used Very Much for Prostate Cancer Detection?

PET is not used very much for detecting prostate cancer spread. For some reason, prostate cancer cells do not seem to rapidly use the radioactively labeled glucose injected for a PET exam. This means that, even if there is prostate cancer that has spread to another area of the body, the PET scan could very well miss it.

By far, the most used (and useful) test for detecting prostate cancer metastases is the bone scan.

Currently, researchers are working to develop new radioactive compounds for PET that may be able to more accurately detect prostate cancer metastases.

References:

Brant and Helms. Fundamentals of Diagnostic Radiology. 2006.

Mayo Clinic. Prostate Cancer. http://www.mayoclinic.org/diseases-conditions/prostate-cancer/basics/definition/con-20029597

Continue Reading