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
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.