Low PSA may not rule out prostate cancer

Even if patients have relatively low prostate specific antigen (PSA) levels, a biological marker for the disease, abnormalities detected by digital rectal examination (DRE) can help identify prostate cancer, re-enforcing the importance of this procedure, new study findings suggest.

Some doctors believe the use of DRE in patients with low serum PSA levels - lower than 4 ng/mL - is not necessary.

To further investigate, Dr. Caleb B. Bozeman and colleagues at Louisiana State University Health Sciences Center in Shreveport identified 916 patients with abnormal DRE findings and a PSA level lower than 4.0 ng/mL. Most patients underwent standard rectal biopsies.

According to the team's paper, published in the medical journal Urology, prostate cancer was diagnosed in 81 men, or 8.8 percent.

The investigators found that the predictive value of the DRE increased as PSA levels increased, with cancer detected in 1.8 percent of those with levels between 0.0 and 0.9 ng/mL, versus 21 percent among those with levels between 3.0 and 3.9 ng/mL.

Age was also a significant predictor, with cancer diagnosed among 5.4 percent of those younger than 50 years and among 11.3 percent older than 70 years.

The authors also noted that during surgery, 19 percent of the prostate cancers were diagnosed on the side opposite the original abnormality, defined as "serendipitous detection."

"Our study found that the abnormality on the DRE in patients diagnosed with prostate cancer was most likely to represent cancer and thus, in most patients, cancer was not diagnosed serendipitously," Bozeman and his associates write.

However, they add, "one could argue that patients with abnormal DRE findings and a serum PSA less than 2.0 ng/mL could simply be followed up closely and do not require a prostate biopsy."

SOURCE: Urology, October 2005.