PSA Test (Prostate Specific Antigen)

  • Medical Author: Pamela I. Ellsworth, MD
  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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What is PSA velocity and PSA doubling time?

Change in PSA levels over time can be used to assess both cancer risk and aggressiveness of the particular tumor. Most urologists use these PSA metrics to help drive patient counseling and care. PSA velocity is defined as an absolute annual increase in serum PSA (ng/mL/year). PSA doubling time is the time it takes the PSA value to increase by 100%, or double. These two measures also have a significant prognostic role in patients that have already been treated for prostate cancer (with either surgery [radical prostatectomy] or radiotherapy [external beam or brachytherapy]). However, studies have shown that using values of these PSA measures for prostate cancer diagnosis do not provide additional information compared to PSA level alone.

How is PSA testing used for pretreatment staging of prostate cancer?

Once prostate cancer is diagnosed by the presence of cancer cells on prostate biopsy and assigned a cancer grade (Gleason score), PSA is used in combination with the grade of the prostate cancer to determine further medical studies needed for cancer staging. Staging (otherwise viewed as the extent of spread of the cancer within the body, or "Where in the body are the cancer cells?") determines if the cancer is localized or metastatic. Staging therefore drives the best management and appropriate treatment for the cancer. As mentioned earlier, serum PSA levels correlate with the risk of prostate cancer extension outside of the prostate including seminal vesicle invasion and lymph node involvement. The proportion of men with cancer confined to the prostate is about 80% when the PSA level at diagnosis is less than 4.0 ng/mL; about 70% when the PSA level is between 4.0 and 10.0 ng/mL; and about 50% when the PSA level is greater than 10.0 ng/mL. This is why patients with serum PSA levels of less than 10.0 ng/mL are most likely to respond well to local therapy such as prostatectomy (surgical removal of the prostate) or external beam radiation (radiation therapy). The need for additional medical tests such as a bone scan and CT scan to assess the extent of the prostate cancer will depend on the prostate biopsy results and PSA. Bone scans, used to determine if the prostate cancer has spread to the bones, are recommended if there is high grade prostate cancer present, extensive disease on the biopsy, and PSA > 10-20 ng/mL. CT scan is used to assess for pelvic lymph node enlargement suggestive of prostate cancer metastases to the lymph nodes and is recommended for individuals with high grade prostate cancer and PSA > 10 ng/mL. Over the past few decades, several predictive tools (otherwise called nomograms) have included the PSA in their parameters to predict posttreatment outcomes. These nomograms include the Partin and Kattan nomograms from Memorial Sloan Kettering. For instance, the Kattan nomogram is an online predictive tool that is available to the public (https://www.mskcc.org/nomograms/prostate).

Medically Reviewed by a Doctor on 2/1/2017

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