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Dosimetric Analysis of an MRI Assisted Focal Boost Integrated with HDR Monotherapy for Low and Intermediate Risk Prostate Cancer
S200
Abstracts / Brachytherapy 15 (2016) S21eS204
prescription dose was prescribed such that the CTV V100%O95% while the CTV V200%!15%, V150%!30%, and V125%!60%. The OAR constraints were: V115% !1cc and Dmax!125% for the urethra, V75%! 1cc for the bladder and V75%!1cc for the rectum. Results: For prostate glands ranging in sizes of 25.6 to 62.4 cc, with a median of 39.4 cc, achievable volumes of dose escalation were found to be in the range of VDE_120%5 91-97% and VDE_130%582-89% if the stated OAR constraints are strictly enforced. The results indicate 30% dose escalation to the general disease extension volume would require modification of current OAR constraints if greater than 90% coverage of the VDE is desired. For 20% dose escalation, while the exact degree of the VDE coverage is variably dependent on the patient anatomy, coverage at 90% level was generally achievable for the studied group. Conclusions: Further dose escalation to the zone of disease extension probability is achievable through redistribution of hot-spots within the confines of current OAR constraints. Specifically, the study indicates that delivering a 20% integrated HDR boost to 90% of the zonal extension of positive lesion may be dosimetrically feasible. In comparison to MRguided dose escalation of dominant intraprostatic lesions, the technique involves escalating a larger volume associated with elevated disease extension probability. As a practical alternative to MR-guided doseescalation relying on commonly available DRE and biopsy information, the technique may provide greater simplicity in the implant process, and enhanced value in the cost effective management of prostate cancer.
PO219 Dosimetric Analysis of an MRI Assisted Focal Boost Integrated with HDR Monotherapy for Low and Intermediate Risk Prostate Cancer Laura D’Alimonte, BSc, MHSc, Joelle Helou, MD, Gerard Morton, MD, Ananth Ravi, PhD, Hans Chung, MD, Merrylee McGuffin, BSc, MSc, Andrew Loblaw, MD, Andrew Loblaw, MD. Odette Cancer Centre, Sunnybrook Health Science Centre, Toronto, ON, Canada. Purpose: Prostate high dose rate (HDR) brachytherapy as monotherapy is an emerging treatment option for men with low/intermediate risk disease. With the availability of advanced imaging, there is an opportunity to further dose escalate to the dominant intraprostatic lesion. We describe the dosimetric outcomes of an MRI assisted focal boost integrated with HDR monotherapy for low and intermediate risk prostate cancer. Methods: Eligible patients for this prospective, phase I/II study had lowand intermediate risk prostate cancer, IPSS < 16, were medically eligible for HDR and had a dominant intraprostatic lesion (DIL) on multiparametric MRI (mpMRI) prior to brachytherapy. No androgen deprivation therapy was allowed. At the time of brachytherapy, cognitive co-registration or radially weighted contour based deformable registration was performed to delineate the DIL volume. There was a 0-5mm expansion of the DIL (constrained by prostate or normal tissues) to define the DIL PTV. Patients were treated with 19Gy x 1 to the prostate. Planning dose constraints were defined based on previous experience: prostate V100 > 95%, V200 ! 12%, urethra D10 ! 118%, rectum V80 < 0.5cc, DIL PTV D90 > or equal to 23Gy. Results: A total of 15 patients have undergone HDR monotherapy treatment; median follow up of 6 weeks. The median age was 68 years (range 56-73). At presentation, median PSA was 6.12ng/mL (range 2.911.4). Two, 7 and 6 patients had low, low-intermediate and highintermediate risk disease. Baseline MRI characteristics were PIRADS 5 (n510), and PIRAD 4 (n55) with a median DIL size 14.5mm (range 525). Mean prostate volume was 36.9cc (range 17-53). Ten and 5 patients had cognitive and deformable co-registration. The median DIL PTV D90 was 25 Gy (132% of the prescription dose; range: 21-31 Gy). The mean prostate V100 was 97% (range 95-99%), mean prostate V200 was 10.1% (range 8-15%). The mean urethra D10 was 116% (range 115-118%) and a mean rectal V80 of 0.112cc (range 0-0.41). No grade 3 acute GI or GU side effects have been observed. Conclusions: The use of mpMRI to define and further escalate dose to the intraprostatic lesion using HDR monotherapy is achievable without comprising any other planning objectives. Patients will continue to be
followed prospectively to measure toxicity, efficacy, quality of life, costutility and cost-effectiveness.
PO220 Preliminary Results of MR-Guided Focal Salvage HDR Brachytherapy for Locally Recurrent Prostate Cancer after Primary Radiotherapy Peter Chung, MBChB1,2, Alejandro Berlin, MD1,2, Alex Rink, PhD1,2, Marco Carlone, PhD1,2, Jessy Abed, BSc1, Anna Simeonov, BSc1, Gerald O’Leary, MD1,2, Andrew Bayley, MD1,2, Charles Catton, MD1,2, Robert Bristow, MD1,2, Bernadeth Lao, BSc1, Cynthia Menard, MD1,2. 1Princess Margaret Cancer Centre, Toronto, ON, Canada; 2University of Toronto, Toronto, ON, Canada. Purpose: To report preliminary outcomes of focal salvage MR-guided HDR brachytherapy for locally recurrent prostate cancer after external beam radiotherapy (EBRT). Materials and Methods: Patients entered on this prospective study had biopsy proven local recurrence of prostate carcinoma visible on MRI, with a PSA doubling time O 6 months, at least 18 months after definitive external beam radiotherapy. The GTV was defined prior to the brachytherapy procedure using multiparametric MRI (T2-weighted, diffusion-weighted, dynamic contrast-enhanced) and biopsy acquired during transperineal MR-guided mapping biopsy. The prostate gland and GTV contours were deformably co-registered to T2w images obtained at the time of brachytherapy after catheter placement using a biomechanical-based deformable image registration (MORFEUS). CTV margin expansion (5 mm in all directions) was restricted to adjacent OARs and 2 mm beyond the prostate boundary where applicable. PTV margins of 2 mm cranio-caudally and 1mm elsewhere were then applied. Focal HDR brachytherapy was delivered to a total dose of 26 Gy in two separate implants 7-14 days apart. Patients received no androgen deprivation therapy. Results: 15 patients were enrolled; median follow-up was 12 months (range, 3-24). The median age at time of enrollment was 72 years (range, 62-77). The median pre-salvage treatment PSA was 3.96 ng/ml (range, 1.68 - 8.39). All 15 patients had a single GTV. Median GTV and PTV volumes were 1.45 cc (range, 0.66-6.76) and 6.45 cc (range 3.5-17.39), respectively. A median of 8 catheters (range, 4-12) were required for the focal implants. All 15 patients had an initial biochemical response after salvage brachytherapy with 14 having more than 50% reduction from baseline. To date 10 patients have achieved PSA ! 1 ng/ml, while 9 of 12 patients with O 12 months follow up have PSA level ! 1ng/ml. Of 2 patients who have experienced biochemical failure, 1 had sufficient follow-up to have imaging and biopsy evidence of a marginal local recurrence but neither has developed evidence of metastatic disease. Acute toxicity (CTCAE v4.0) was mild. Only one patient had grade 2 toxicity (urinary obstruction requiring temporary catherisation after his second implant). All acute toxicity has resolved in patients who have greater than 3 months of follow-up. Conclusions: These early results suggest that in selected patients, MRguided focal salvage HDR brachytherapy is associated with minimal acute toxicity and initial biochemical response appears promising. Further follow up will determine if this approach results in acceptable local oncologic control with minimal associated late toxicity in the re-treatment setting.
PO221 Implementation of Process Mapping to Improve a Clinical Workflow: A Study with Our Low Dose Rate Prostate Brachytherapy Program Sunita Boddu, PhD, Brian Massingill, MS, Sangroh Kim, PhD, Andrew Morrow, MS, Dharanipathy Rangaraj, PhD. Radiation Oncology, Baylor Scott & White Healthcare, Temple, TX, USA. Purpose: To implement low dose rate (LDR) prostate brachytherapy process mapping for continual process improvement and to provide
Abstracts / Brachytherapy 15 (2016) S21eS204
prescription dose was prescribed such that the CTV V100%O95% while the CTV V200%!15%, V150%!30%, and V125%!60%. The OAR constraints were: V115% !1cc and Dmax!125% for the urethra, V75%! 1cc for the bladder and V75%!1cc for the rectum. Results: For prostate glands ranging in sizes of 25.6 to 62.4 cc, with a median of 39.4 cc, achievable volumes of dose escalation were found to be in the range of VDE_120%5 91-97% and VDE_130%582-89% if the stated OAR constraints are strictly enforced. The results indicate 30% dose escalation to the general disease extension volume would require modification of current OAR constraints if greater than 90% coverage of the VDE is desired. For 20% dose escalation, while the exact degree of the VDE coverage is variably dependent on the patient anatomy, coverage at 90% level was generally achievable for the studied group. Conclusions: Further dose escalation to the zone of disease extension probability is achievable through redistribution of hot-spots within the confines of current OAR constraints. Specifically, the study indicates that delivering a 20% integrated HDR boost to 90% of the zonal extension of positive lesion may be dosimetrically feasible. In comparison to MRguided dose escalation of dominant intraprostatic lesions, the technique involves escalating a larger volume associated with elevated disease extension probability. As a practical alternative to MR-guided doseescalation relying on commonly available DRE and biopsy information, the technique may provide greater simplicity in the implant process, and enhanced value in the cost effective management of prostate cancer.
PO219 Dosimetric Analysis of an MRI Assisted Focal Boost Integrated with HDR Monotherapy for Low and Intermediate Risk Prostate Cancer Laura D’Alimonte, BSc, MHSc, Joelle Helou, MD, Gerard Morton, MD, Ananth Ravi, PhD, Hans Chung, MD, Merrylee McGuffin, BSc, MSc, Andrew Loblaw, MD, Andrew Loblaw, MD. Odette Cancer Centre, Sunnybrook Health Science Centre, Toronto, ON, Canada. Purpose: Prostate high dose rate (HDR) brachytherapy as monotherapy is an emerging treatment option for men with low/intermediate risk disease. With the availability of advanced imaging, there is an opportunity to further dose escalate to the dominant intraprostatic lesion. We describe the dosimetric outcomes of an MRI assisted focal boost integrated with HDR monotherapy for low and intermediate risk prostate cancer. Methods: Eligible patients for this prospective, phase I/II study had lowand intermediate risk prostate cancer, IPSS < 16, were medically eligible for HDR and had a dominant intraprostatic lesion (DIL) on multiparametric MRI (mpMRI) prior to brachytherapy. No androgen deprivation therapy was allowed. At the time of brachytherapy, cognitive co-registration or radially weighted contour based deformable registration was performed to delineate the DIL volume. There was a 0-5mm expansion of the DIL (constrained by prostate or normal tissues) to define the DIL PTV. Patients were treated with 19Gy x 1 to the prostate. Planning dose constraints were defined based on previous experience: prostate V100 > 95%, V200 ! 12%, urethra D10 ! 118%, rectum V80 < 0.5cc, DIL PTV D90 > or equal to 23Gy. Results: A total of 15 patients have undergone HDR monotherapy treatment; median follow up of 6 weeks. The median age was 68 years (range 56-73). At presentation, median PSA was 6.12ng/mL (range 2.911.4). Two, 7 and 6 patients had low, low-intermediate and highintermediate risk disease. Baseline MRI characteristics were PIRADS 5 (n510), and PIRAD 4 (n55) with a median DIL size 14.5mm (range 525). Mean prostate volume was 36.9cc (range 17-53). Ten and 5 patients had cognitive and deformable co-registration. The median DIL PTV D90 was 25 Gy (132% of the prescription dose; range: 21-31 Gy). The mean prostate V100 was 97% (range 95-99%), mean prostate V200 was 10.1% (range 8-15%). The mean urethra D10 was 116% (range 115-118%) and a mean rectal V80 of 0.112cc (range 0-0.41). No grade 3 acute GI or GU side effects have been observed. Conclusions: The use of mpMRI to define and further escalate dose to the intraprostatic lesion using HDR monotherapy is achievable without comprising any other planning objectives. Patients will continue to be
followed prospectively to measure toxicity, efficacy, quality of life, costutility and cost-effectiveness.
PO220 Preliminary Results of MR-Guided Focal Salvage HDR Brachytherapy for Locally Recurrent Prostate Cancer after Primary Radiotherapy Peter Chung, MBChB1,2, Alejandro Berlin, MD1,2, Alex Rink, PhD1,2, Marco Carlone, PhD1,2, Jessy Abed, BSc1, Anna Simeonov, BSc1, Gerald O’Leary, MD1,2, Andrew Bayley, MD1,2, Charles Catton, MD1,2, Robert Bristow, MD1,2, Bernadeth Lao, BSc1, Cynthia Menard, MD1,2. 1Princess Margaret Cancer Centre, Toronto, ON, Canada; 2University of Toronto, Toronto, ON, Canada. Purpose: To report preliminary outcomes of focal salvage MR-guided HDR brachytherapy for locally recurrent prostate cancer after external beam radiotherapy (EBRT). Materials and Methods: Patients entered on this prospective study had biopsy proven local recurrence of prostate carcinoma visible on MRI, with a PSA doubling time O 6 months, at least 18 months after definitive external beam radiotherapy. The GTV was defined prior to the brachytherapy procedure using multiparametric MRI (T2-weighted, diffusion-weighted, dynamic contrast-enhanced) and biopsy acquired during transperineal MR-guided mapping biopsy. The prostate gland and GTV contours were deformably co-registered to T2w images obtained at the time of brachytherapy after catheter placement using a biomechanical-based deformable image registration (MORFEUS). CTV margin expansion (5 mm in all directions) was restricted to adjacent OARs and 2 mm beyond the prostate boundary where applicable. PTV margins of 2 mm cranio-caudally and 1mm elsewhere were then applied. Focal HDR brachytherapy was delivered to a total dose of 26 Gy in two separate implants 7-14 days apart. Patients received no androgen deprivation therapy. Results: 15 patients were enrolled; median follow-up was 12 months (range, 3-24). The median age at time of enrollment was 72 years (range, 62-77). The median pre-salvage treatment PSA was 3.96 ng/ml (range, 1.68 - 8.39). All 15 patients had a single GTV. Median GTV and PTV volumes were 1.45 cc (range, 0.66-6.76) and 6.45 cc (range 3.5-17.39), respectively. A median of 8 catheters (range, 4-12) were required for the focal implants. All 15 patients had an initial biochemical response after salvage brachytherapy with 14 having more than 50% reduction from baseline. To date 10 patients have achieved PSA ! 1 ng/ml, while 9 of 12 patients with O 12 months follow up have PSA level ! 1ng/ml. Of 2 patients who have experienced biochemical failure, 1 had sufficient follow-up to have imaging and biopsy evidence of a marginal local recurrence but neither has developed evidence of metastatic disease. Acute toxicity (CTCAE v4.0) was mild. Only one patient had grade 2 toxicity (urinary obstruction requiring temporary catherisation after his second implant). All acute toxicity has resolved in patients who have greater than 3 months of follow-up. Conclusions: These early results suggest that in selected patients, MRguided focal salvage HDR brachytherapy is associated with minimal acute toxicity and initial biochemical response appears promising. Further follow up will determine if this approach results in acceptable local oncologic control with minimal associated late toxicity in the re-treatment setting.
PO221 Implementation of Process Mapping to Improve a Clinical Workflow: A Study with Our Low Dose Rate Prostate Brachytherapy Program Sunita Boddu, PhD, Brian Massingill, MS, Sangroh Kim, PhD, Andrew Morrow, MS, Dharanipathy Rangaraj, PhD. Radiation Oncology, Baylor Scott & White Healthcare, Temple, TX, USA. Purpose: To implement low dose rate (LDR) prostate brachytherapy process mapping for continual process improvement and to provide