Some Men with Low PSAs Have Prostate Cancer

Men with low PSA (prostate specific antigen) levels on screening tests can still have prostate cancer, according to a study released by scientists from the National Cancer Institute (NCI), part of the National Institutes of Health, and the Southwest Oncology Group, an NCI-funded network of researchers. In this study, prostate cancers were detected by biopsy in men with normal PSA levels.

Since the late 1980s, PSA tests have been widely used in the United States in an attempt to detect prostate cancer at an early stage. However, PSA testing has never been proven to reduce the risk of dying from prostate cancer. Not all prostate cancer detected by PSA screening is clinically relevant and, therefore, screening carries a risk of "over-diagnosing" the disease, which could lead to unnecessary surgery or radiation therapy. Thus, PSA testing is not a universally recommended screening procedure. An ongoing NCI study is addressing the issue of whether PSA screening reduces the risk of death from prostate cancer.

Importantly, the study also found that only 2.3 percent of men in the PCPT control arm with PSA levels of 4 ng/ml or less had high-grade cancers. For men with a PSA of 2 or lower, the chance of having a high-grade cancer was even lower––1.4 percent. Grade was measured by Gleason score, a system that ranks tumors from 2 to 10 based on their appearance under the microscope. High-grade tumors––Gleason scores of 7 to 10––often grow more quickly and may be more likely to spread than lower-grade tumors.

Prostate cancer is the most common cancer in men, after skin cancer. It estimated that approximately 230,110 men in the United States will be diagnosed with the disease this year, and about 30,000 men will die from it.