“The risk of identifying clinically insignificant cancers appropriately tempers enthusiasm for serial biopsy,” comment Dr. Osama M. Zaytoun and colleagues.
As they explain, most prostate cancers are detected on the initial biopsy or after one repeat biopsy, but “persistent suspicion of prostate cancer occasionally leads to serial biopsy.” However, the rate of detection declines with the number of repeat biopsies, and the clinical significance of detected cancers appears to decline also.
To investigate these issues, the team analyzed cancer detection rates and the likelihood of detecting significant vs insignificant tumors in 479 men who underwent 749 repeat biopsies after two prior negative results. Biopsy protocols were either extended schemes involving 10-14 cores or saturation protocols of more than 20 cores.
Cancer was detected eventually in 119 of the patients (24.8%), the investigators found, but 75 of these positive biopsies (63%) revealed clinically insignificant cancer — defined as having a Gleason score <3, no more than 3 positive cores, and cancer involvement in any positive core no more than 50%.
Dr. Zaytoun and colleagues conclude that the threshold for a repeat biopsy should be “very high” after more than one negative session, weighing the odds of detecting insignificant cancer against the risk of missing significant tumors.
“Patients with clear indication to consider serial biopsies are those with ASAP (atypical small acinar proliferation), or multifocal HPGIN (high-grade prostatic intraepithelial neoplasia) as part of a delayed interval biopsy protocol,” they advise.
On the other hand, “Patients with truly benign findings are strongly encouraged to forego future serial biopsy in the absence of significant changes in clinical suspicion, including changes in DRE, doubling of PSA level or development of very low %fPSA (percentage free/total PSA.).”