V08-07: Prostate Cancer: Use of Targeted Biopsy Information for Planning Partial Gland Ablation with High-Intensity Focused Ultrasound
High-intensity focused ultrasound (HIFU) can be used to ablate prostate cancer (CaP) focally, non-invasively, and with minimal side effects. In this video, we present a method for focal HIFU, employing (1) multiparametric magnetic resonance imaging (mpMRI), (2) fusion biopsy, (3) margin generation, and (4) treatment.
After mpMRI is performed, prostate regions suspicious for CaP (PIRADSv2) are identified and contoured by an experienced radiologist. Suspicious regions receive targeted biopsy with an MRI-ultrasound fusion system; 10-12 systematic cores are also obtained. Patients are potentially eligible for focal HIFU if they harbor a single focus of organ-confined, clinically significant disease with Gleason Score (GS) ≤ 4+3 and prostate volume ≤ 55 CC. To generate a treatment margin, the original MR target is expanded 1 to 2 cm; prior studies informed our use of asymmetrical margins that were largest along the base-apex axis (Priester, J.Urol. 2016). Next, the biopsy coordinates are imported, and the margin is refined by excluding CaP-negative cores with ≥ 1 cm of tissue. Lastly, anatomic regions can be excluded from treatment. The urethra is spared whenever possible, with the risk of side effects weighed against the possibility of positive margins. The plan (Fig 1) is visualized and reviewed using open source software (3D Slicer). All surfaces (prostate, MR target, biopsy cores, margin, and urethra) are then exported to the HIFU device and overlaid on real-time ultrasound. Patients receive follow-up mpMRI and biopsy at 6 months.
To date, this method has been used for focal HIFU in 20 patients. Plan generation is semi-automated and takes about 30 minutes. On average, 9.4 CC (29% of prostate tissue) was treated using these margins, with reduced treatment time relative to hemi- or whole-gland HIFU. Of 7 patients with 6-month follow-up biopsy, none had residual pattern 4 disease, but 3 of 7 had small-volume GS = 3+3.
Treatment margins can be created in a patient-specific manner, incorporating data from MRI, fusion biopsy, and prostate anatomy. This approach helps to ensure cancer control while minimizing procedure time and damage to healthy tissue.
Funding: This work was funded in part by the Jean Perkins Foundation and by Award Number R01CA158627 from the National Cancer Institute.