How Is It Possible to Have Really Low PSA & Prostate Cancer?

By Lorra Garrick | Last updated 04/25

Medically reviewed by Sean Cavanaugh, MD

A very low PSA but aggressive prostate cancer?

Yes, for three reasons. “Most prostate cancers produce PSA,” says Sean Cavanaugh, MD, a radiation oncologist with GenesisCare, a premier provider of cancer and urology care.

But there are times when prostate cancer is present along with a low PSA value.

“However, it is possible for a cancer cell line to dedifferentiate (mutate) and stop PSA production,” continues Dr. Cavanaugh.

“This could result in a patient with cancer, perhaps even a very aggressive cancer, but a normal or even low PSA. This is quite rare.

“In addition, men on anti-testosterone therapy might register a low or even zero PSA while still having viable cancer cells.

“Finally, post-prostatectomy or post-radiation patients generally have a low PSA, but as time passes some learn that they still have active cancer.”

The PSA, which is obtained via a blood test and stands for prostate specific antigen, can also be high in a man who does not have any malignancy.

Nevertheless, this biomarker is a valuable tool to physicians as a guide for how to proceed next in a patient who’s experiencing concerning symptoms such as frequent urination, difficulty with starting or stopping a urine stream, pain with urination or ejaculation, blood in the urine and pain in the lower back.

The American Cancer Society recommends that men who have an average risk of prostate cancer begin getting tested at age 50 if they’re already healthy enough to expect to live another 10 years.