Study Indicates Need for Lower PSAD Cutoff

February 1, 1997

CHICAGO--According to the clinical literature, men with a prostate-specific antigen density (PSAD) level less than 0.15 ng/mL do not need ultrasound-guided biopsy because the PSAD is considered normal or reflects only a benign process.

CHICAGO--According to the clinical literature, men with a prostate-specificantigen density (PSAD) level less than 0.15 ng/mL do not need ultrasound-guidedbiopsy because the PSAD is considered normal or reflects only a benignprocess.

However, in a series from Albany Medical College, NY, nearly 25% ofmen with prostate cancer had a PSAD below 0.15 ng/mL, and nearly 80% ofthese men were found to have a clinically significant midgrade prostatecancer. Thus, a lower cutoff point should be used to distinguish normalor benign levels of PSAD from potentially malignant ones, Maria Bajas,MD, said at the Radiological Society of North America annual meeting.

"PSA levels can rise because of a number of processes besides cancer,"Dr. Bajas said. To help differentiate benign from malignant effects onPSA, more specific calculations, such as PSAD, which relates PSA to thevolume of the prostate gland, have been utilized.

Although a PSAD level of 0.15 ng/mL is the most common threshold fordetermining when biopsy is warranted, other levels, such as 0.12 and 0.10ng/mL, also have been suggested as appropriate cutoff points. "Thequestion is, which PSAD level is best for picking up those cancers thatare clinically important," she said.

Dr. Bajas and her colleagues, led by Matthew D. Rifkin, MD, retrospectivelyreviewed the records of 600 consecutive men who had been referred to AlbanyMedical College for prostate ultrasound and biopsy because of an abnormaldigital rectal examination or PSA level greater than 4 ng/mL.

The 166 men who had prostate cancer confirmed at biopsy were dividedinto three groups based on PSAD measurements of 0.10, 0.12, and 0.15 ng/mL,and their tumors were pathologically categorized as having low, medium,or high Gleason grades.

While fewer malignancies were found in men with lower thresholds ofPSAD, a large proportion of the tumors were clinically important, she said.A total of 38 men with prostate cancer had PSAD less than 0.15 ng/mL, "soalmost a quarter of all these men with prostate cancer had a PSAD levelthat is considered to be normal," Dr. Bajas said.

In addition, midgrade tumors were found in 30 (79%) of the 38 men withPSAD below 0.15 ng/mL, 17 (81%) of 21 men whose PSAD was below 0.12 ng/mL,and 13 (86%) of 15 men with PSAD less than 0.10 ng/mL.

Even though the number of negative biopsies will rise as the thresholdof PSAD falls, Dr. Bajas recommends that all men with high PSA levels shouldhave ultrasound-guided biopsy if their PSAD is above 0.10 ng/mL, regardlessof the results of digital rectal examination.