By Will Boggs MD
NEW YORK (Reuters Health) - Extensive transrectal repeat biopsy with anterior sampling lacks utility for general use in men on active surveillance for low-risk prostate cancer, but it may be appropriate for those with higher prostate-specific antigen (PSA) density, researchers from Sweden report.
"The strong relation between PSA density and high-grade cancer in the anterior prostate was surprising and is of immediate clinical relevance," Dr. Ola Bratt from Sahlgrenska Academy at the University of Gothenburg told Reuters Health by email.
Repeat biopsy is considered essential for men with low-grade prostate cancer who are on active surveillance, but the optimal number and distribution of cores are unknown.
Dr. Bratt and colleagues in the Study of Active Monitoring in Sweden (SAMS) randomized clinical trial, which is comparing a standard protocol for active surveillance with an experimental protocol in which the first repeat transrectal biopsy is more extensive and subsequent follow-up is less frequent, analyzed the outcome of the initial repeat biopsy to assess the value of the extensive biopsy template with anterior sampling.
In the first repeat biopsy, scheduled within the first six months of diagnosis, the median number of biopsy cores was higher in the extensive-biopsy group (19, with a median four directed anteriorly) than in the control biopsy group (12), the team reports in European Urology, online March 13.
The primary outcome measure, detection of Gleason grade 2 or higher cancer, was 16% of 156 men who had an extensive repeat biopsy with anterior sampling, compared to 10% of 164 men who had a standard repeat biopsy (p=0.09).
Overall, 34% of men in the extensive-biopsy group with anteriorly directed cores had cancer, with 6.8% of men having cancer identified exclusively in the anterior cores, although none of the six cancers of Gleason grade 3-5 was detected in the anterior cores.
There was a strong linear association between PSA density and cancer in the anteriorly directed biopsy cores, with 2.2-fold greater odds of any cancer and 2.3-fold greater odds of Gleason grade group 2 or higher cancer per 0.1-ng/mL/cc increase in PSA density.
Among men with PSA density of at least 0.15 ng/mL/cc, commonly used to define the very-low-risk category, Gleason grade group 2 or higher cancer was detected in 19% of anteriorly directed cores, compared with only 5.3% of anteriorly directed cores from men with lower PSA density.
"The trial did not support general use of the extensive transrectal repeat biopsy template, but cancer in the anteriorly directed cores was common, particularly in men with high PSA density," the researchers conclude. "The higher the PSA density, the stronger the reason to include anterior sampling at a systematic repeat biopsy."
"Anterior sampling should be standard when repeat biopsies are taken, at least in men with a PSA density of >0.15 ng/mL/cc who have not had an MRI," Dr. Bratt said.
"There are many unanswered questions about how active-surveillance programs for localized prostate cancer are best designed," he said. "More prospective trials are needed, preferably randomized."
Dr. Leonard S. Marks from David Geffen School of Medicine at UCLA, in Los Angeles, who recently reviewed the role of targeted prostate biopsy in the era of active surveillance, told Reuters Health by email, "The finding of occult cancers in the anterior prostate is an important finding, confirming what others have believed for many years. The hypothesis, that many cancers 'hide' in the anterior prostate, was confirmed, but the way in which it was confirmed, i.e., a form of saturation biopsy, is very old fashioned. In the era of MRI-targeted biopsy, saturation biopsies have disappeared."
"A main value of pre-biopsy MRI is the detection of anterior cancers," said Dr. Marks, who was not involved in the new research. "Only if MRI is not available would these findings change practice."
Eur Urol 2019.