Postimplant Multiparametric Mri-Based Dosimetry After Permanent Iodine Seed Prostate Brachytherapy: The Impact Of The Dose Delivered To The Dominant Intraprostatic Lesion On Prostate-Specific Antigen Bounce

Purpose/Objective(s)The purpose of this study was to determine if post implanted MRI-based dose-volume parameters of the Dominant Intra-prostatic Lesion (DIL) could best predict Prostate Specific Antigen (PSA) bounce occurrence after prostate brachytherapy.Materials/MethodsAll patients had a baseline multi-parametric MRI (mp-MRI) at 3T without an endo-rectal coil in their work-up (T2 weighted + DCE MRI+DW-MRI + proton MR spectroscopy) and were treated with low dose rate 125 I brachytherapy as monotherapy at the dose of 160Gy. MR images were co-registered and matched with the day 30 CT-scan on our dedicated Treatment Planning system (Oncentra, SPOT, The Netherlands). For each patient, the prostate contour was optimized with the help of T2-w MRI contours and the DIL was delineated on DCE-MRI. Then, a new post-implant dosimetry based on CT- MRI fusion was generated: D90%, D95%, V100%, V150% were registered for each DIL and the entire prostate. Bounce was defined as a temporary PSA elevation ≥ 0.2 ng/mL from the baseline previous value followed by a decrease to or below prior nadir without any additional treatment.ResultsFifty-one men were included after a median follow up of 39 months. A PSA bounce occurred in 19 (37%) patients. They were significantly younger than non-bouncers, on average 62 +/- 4 years vs 65 +/- 5 years, p = 0.03. mp-MRI-based dosimetric parameters of the DIL associated with a bounce were lower D90% and V150%. The mean D90% of the DIL was significantly lower in patients who had a PSA spike: 195 +/- 61Gy vs 234 +/- 68Gy, p = 0.047. V150% of the DIL was 60.6% (36.6-80.4) for bouncers while it was 93.9% (51.9-99.3) for non-bouncers, p = 0.039. D90%, D95%, V100% and V150% of the entire prostate were not correlated with the occurrence of a PSA bounce. Bouncers had a significant worse PSA decrease at one year with a mean drop of 4.2ng/mL +/- 1.9 vs 6.64ng/mL +/- 2.9, p = 0.02.ConclusionsA lower D90% and V150% in the DIL were predictive of the occurrence of PSA bounce after PPI, in mp-MRI-based post implanted dosimetry. Focal dose escalation to the DIL may render the follow-up of PPI patients more convenient in the absence of a PSA bounce. Purpose/Objective(s)The purpose of this study was to determine if post implanted MRI-based dose-volume parameters of the Dominant Intra-prostatic Lesion (DIL) could best predict Prostate Specific Antigen (PSA) bounce occurrence after prostate brachytherapy. The purpose of this study was to determine if post implanted MRI-based dose-volume parameters of the Dominant Intra-prostatic Lesion (DIL) could best predict Prostate Specific Antigen (PSA) bounce occurrence after prostate brachytherapy. Materials/MethodsAll patients had a baseline multi-parametric MRI (mp-MRI) at 3T without an endo-rectal coil in their work-up (T2 weighted + DCE MRI+DW-MRI + proton MR spectroscopy) and were treated with low dose rate 125 I brachytherapy as monotherapy at the dose of 160Gy. MR images were co-registered and matched with the day 30 CT-scan on our dedicated Treatment Planning system (Oncentra, SPOT, The Netherlands). For each patient, the prostate contour was optimized with the help of T2-w MRI contours and the DIL was delineated on DCE-MRI. Then, a new post-implant dosimetry based on CT- MRI fusion was generated: D90%, D95%, V100%, V150% were registered for each DIL and the entire prostate. Bounce was defined as a temporary PSA elevation ≥ 0.2 ng/mL from the baseline previous value followed by a decrease to or below prior nadir without any additional treatment. All patients had a baseline multi-parametric MRI (mp-MRI) at 3T without an endo-rectal coil in their work-up (T2 weighted + DCE MRI+DW-MRI + proton MR spectroscopy) and were treated with low dose rate 125 I brachytherapy as monotherapy at the dose of 160Gy. MR images were co-registered and matched with the day 30 CT-scan on our dedicated Treatment Planning system (Oncentra, SPOT, The Netherlands). For each patient, the prostate contour was optimized with the help of T2-w MRI contours and the DIL was delineated on DCE-MRI. Then, a new post-implant dosimetry based on CT- MRI fusion was generated: D90%, D95%, V100%, V150% were registered for each DIL and the entire prostate. Bounce was defined as a temporary PSA elevation ≥ 0.2 ng/mL from the baseline previous value followed by a decrease to or below prior nadir without any additional treatment. ResultsFifty-one men were included after a median follow up of 39 months. A PSA bounce occurred in 19 (37%) patients. They were significantly younger than non-bouncers, on average 62 +/- 4 years vs 65 +/- 5 years, p = 0.03. mp-MRI-based dosimetric parameters of the DIL associated with a bounce were lower D90% and V150%. The mean D90% of the DIL was significantly lower in patients who had a PSA spike: 195 +/- 61Gy vs 234 +/- 68Gy, p = 0.047. V150% of the DIL was 60.6% (36.6-80.4) for bouncers while it was 93.9% (51.9-99.3) for non-bouncers, p = 0.039. D90%, D95%, V100% and V150% of the entire prostate were not correlated with the occurrence of a PSA bounce. Bouncers had a significant worse PSA decrease at one year with a mean drop of 4.2ng/mL +/- 1.9 vs 6.64ng/mL +/- 2.9, p = 0.02. Fifty-one men were included after a median follow up of 39 months. A PSA bounce occurred in 19 (37%) patients. They were significantly younger than non-bouncers, on average 62 +/- 4 years vs 65 +/- 5 years, p = 0.03. mp-MRI-based dosimetric parameters of the DIL associated with a bounce were lower D90% and V150%. The mean D90% of the DIL was significantly lower in patients who had a PSA spike: 195 +/- 61Gy vs 234 +/- 68Gy, p = 0.047. V150% of the DIL was 60.6% (36.6-80.4) for bouncers while it was 93.9% (51.9-99.3) for non-bouncers, p = 0.039. D90%, D95%, V100% and V150% of the entire prostate were not correlated with the occurrence of a PSA bounce. Bouncers had a significant worse PSA decrease at one year with a mean drop of 4.2ng/mL +/- 1.9 vs 6.64ng/mL +/- 2.9, p = 0.02. ConclusionsA lower D90% and V150% in the DIL were predictive of the occurrence of PSA bounce after PPI, in mp-MRI-based post implanted dosimetry. Focal dose escalation to the DIL may render the follow-up of PPI patients more convenient in the absence of a PSA bounce. A lower D90% and V150% in the DIL were predictive of the occurrence of PSA bounce after PPI, in mp-MRI-based post implanted dosimetry. Focal dose escalation to the DIL may render the follow-up of PPI patients more convenient in the absence of a PSA bounce.