Prostate Specific Antigen (cont.)

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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 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). 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. For instance, the Kattan nomogram is an online predictive tool that is available to the public.

How is PSA testing used in the management of prostate cancer after treatment?

A periodic PSA determination is used to detect disease recurrence after treatment. Serum PSA should decrease and remain at undetectable levels after local treatment such as radical prostatectomy. Following initial therapy, a PSA increase indicates recurrence of prostate cancer. For example, if the prostate gland is surgically removed, and all of the cancer is contained within the gland, then the PSA should drop to zero. Similarly, serum PSA should fall to a low level following radiation therapy, high intensity focused ultrasound, and cryotherapy.

If on subsequent testing the PSA test is positive and shows increasing levels, there is a possibility of cancer recurring. In addition, depending upon the PSA level of the increase, it is possible that the cancer has now spread outside of the prostate.

Medically Reviewed by a Doctor on 1/14/2016

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