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Study Indicates Need for Lower PSAD Cutoff

Study Indicates Need for Lower PSAD Cutoff

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.

However, in a series from Albany Medical College, NY, nearly 25% of men with prostate cancer had a PSAD below 0.15 ng/mL, and nearly 80% of these men were found to have a clinically significant midgrade prostate cancer. Thus, a lower cutoff point should be used to distinguish normal or 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 on PSA, more specific calculations, such as PSAD, which relates PSA to the volume of the prostate gland, have been utilized.

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

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

The 166 men who had prostate cancer confirmed at biopsy were divided into 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 of PSAD, 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, "so almost a quarter of all these men with prostate cancer had a PSAD level that is considered to be normal," Dr. Bajas said.

In addition, midgrade tumors were found in 30 (79%) of the 38 men with PSAD 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 threshold of PSAD falls, Dr. Bajas recommends that all men with high PSA levels should have ultrasound-guided biopsy if their PSAD is above 0.10 ng/mL, regardless of the results of digital rectal examination.

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