Sixty-second annual scientific meeting of the canadian organization of medical physicists
Sci-Fri AM: MRI and Diagnostic Imaging - 04: How does prostate biopsy guidance error impact pathologic cancer risk assessment?
MRI-targeted, 3D transrectal ultrasound (TRUS)-guided prostate biopsy aims to reduce the 21–47% false negative rate1 of clinical 2D TRUS-guided sextant biopsy, but still has a substantial false negative rate. This could be improved via biopsy needle target optimization, accounting for uncertainties due to guidance system errors and image registration errors. As an initial step toward this broader goal, we elucidated the impact of biopsy needle delivery error on the probability of obtaining tumour samples and on core involvement. These are both important parameters to patient risk stratification and treatment decision.
We investigated this for cancer of all grades, and separately for intermediate/high grade (≥Gleason 4+3) cancer. We used expert-contoured gold-standard prostatectomy histology to simulate targeted biopsies using an isotropic Gaussian needle delivery error from 1 to 6 mm, and investigated the amount of cancer obtained in each biopsy core as determined by histology.
Needle delivery error resulted in core involvement variability that could influence treatment decisions; the presence or absence of cancer in 1/3 or more of each needle core can be attributed to needle delivery error of 4 mm (as observed in practice2).
Repeated biopsies of the same tumour target can yield percent core involvement measures with sufficient variability to influence the decision between active surveillance and treatment. However, this may be mitigated by making more than one biopsy attempt at selected tumour targets.