Abstract
PurposeThis study reports on the development of a novel 3D procedure planning technique to provide pre-ablation treatment planning for partial gland prostate cryoablation (cPGA).MethodsTwenty men scheduled for partial gland cryoablation (cPGA) underwent pre-operative image segmentation and 3D modeling of the prostatic capsule, index lesion, urethra, rectum, and neurovascular bundles based upon multi-parametric MRI data. Pre-treatment 3D planning models were designed including virtual 3D cryotherapy probes to predict and plan cryotherapy probe configuration needed to achieve confluent treatment volume. Treatment efficacy was measured with 6 month post-operative MRI, serum prostate specific antigen (PSA) at 3 and 6 months, and treatment zone biopsy results at 6 months. Outcomes from 3D planning were compared to outcomes from a series of 20 patients undergoing cPGA using traditional 2D planning techniques.ResultsForty men underwent cPGA. The median age of the cohort undergoing 3D treatment planning was 64.8 years with a median pretreatment PSA of 6.97 ng/mL. The Gleason grade group (GGG) of treated index lesions in this cohort included 1 (5%) GGG1, 11 (55%) GGG2, 7 (35%) GGG3, and 1 (5%) GGG4. Two (10%) of these treatments were post-radiation salvage therapies. The 2D treatment cohort included 20 men with a median age of 68.5 yrs., median pretreatment PSA of 6.76 ng/mL. The Gleason grade group (GGG) of treated index lesions in this cohort included 3 (15%) GGG1, 8 (40%) GGG2, 8 (40%) GGG3, 1 (5%) GGG4. Two (10%) of these treatments were post-radiation salvage therapies. 3D planning predicted the same number of cryoprobes for each group, however a greater number of cryoprobes was used in the procedure for the prospective 3D group as compared to that with 2D planning (4.10 ± 1.37 and 3.25 ± 0.44 respectively, p = 0.01). At 6 months post cPGA, the median PSA was 1.68 ng/mL and 2.38 ng/mL in the 3D and 2D cohorts respectively, with a larger decrease noted in the 3D cohort (75.9% reduction noted in 3D cohort and 64.8% reduction 2D cohort, p 0.48). In-field disease detection was 1/14 (7.1%) on surveillance biopsy in the 3D cohort and 3/14 (21.4%) in the 2D cohort, p = 0.056) In the 3D cohort, 6 month biopsy was not performed in 4 patients (20%) due to undetectable PSA, negative MRI, and negative MRI Axumin PET. For the group with traditional 2D planning, treatment zone biopsy was positive in 3/14 (21.4%) of the patients, p = 0.056.Conclusions3D prostate cancer models derived from mpMRI data provide novel guidance for planning confluent treatment volumes for cPGA and predicted a greater number of treatment probes than traditional 2D planning methods. This study prompts further investigation into the use of 3D treatment planning techniques as the increase of partial gland ablation treatment protocols develop.
Highlights
The utilization of multiparametric magnetic resonance imaging in the diagnostic paradigm for prostate cancer has emerged as the primary imaging modality utilized to identify and characterize clinically significant prostate cancer [1,2,3,4,5]
3D prostate cancer models derived from multiparametric magnetic resonance imaging (mpMRI) data provide novel guidance for planning confluent treatment volumes for cPGA and predicted a greater number of treatment probes than traditional 2D planning methods
To address the inadequacies inherent to 2D mapping techniques, this study reports on the development of a novel 3D procedure planning technique to provide preablation treatment planning for cPGA
Summary
The utilization of multiparametric magnetic resonance imaging (mpMRI) in the diagnostic paradigm for prostate cancer has emerged as the primary imaging modality utilized to identify and characterize clinically significant prostate cancer [1,2,3,4,5]. Coupling mpMRI with targeted prostate biopsy using MRI ultrasound fusion increases detection of clinically significant prostate cancer and enables accurate disease localization opening the possibility of targeted treatment via prostate gland ablation (PGA) [3, 6, 7]. While mpMRI accurately identifies disease location, multiple studies demonstrate that it underestimates the exact tumor volume, up to 30% in some studies [8,9,10]. This volume underestimation results in the need to increase the amount of prostate treated in order to ensure ablation of the MR-visible tumor as well as the invisible boundaries. Reported outcomes for prostate cryoablation demonstrate positive biopsy rates from 12% to 38% [17,18,19,20]
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