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Title: Exploring the Margin Recipe for Online Adaptive Radiation Therapy for Intermediate-Risk Prostate Cancer: An Intrafractional Seminal Vesicles Motion Analysis

Abstract

Purpose: To provide a benchmark for seminal vesicle (SV) margin selection to account for intrafractional motion and to investigate the effectiveness of 2 motion surrogates in predicting intrafractional SV coverage. Methods and Materials: Fifteen prostate patients were studied. Each patient had 5 pairs (1 patient had 4 pairs) of pretreatment and posttreatment cone beam CTs (CBCTs). Each pair of CBCTs was registered on the basis of prostate fiducial markers. All pretreatment SVs were expanded with 1-, 2-, 3-, 4-, 5-, and 8-mm isotropic margins to form a series of planning target volumes, and their intrafractional coverage to the posttreatment SV determined the “ground truth” for exact coverage. Two motion surrogates, the center of mass (COM) and the border of contour, were evaluated by the use of Pearson product-moment correlation coefficient and exponential fitting for predicting SV underdosage. Action threshold of each surrogate was calculated. The margin for each surrogate was calculated according to a traditional margin recipe. Results: Ninety-five percent posttreatment SV coverage was achieved in 9%, 53%, 73%, 86%, 95%, and 97% of fractions with 1-, 2-, 3-, 4-, 5-, and 8-mm margins, respectively. The 5-mm margins provided 95% intrafractional SV coverage in over 90% of fractions. The correlationmore » between the COM and border was weak, moderate, and strong in the left-right (L-R), anterior-posterior (A-P), and superior-inferior (S-I) directions, respectively. Exponential fitting gave the underdosage threshold of 4.5 and 7.0 mm for the COM and border. The Van Herk margin recipe recommended 0-, 0.5-, and 0.8-mm margins in the L-R, A-P, and S-I directions based on the COM, and 1.2-, 3.9-, and 2.5-mm margins based on the border. Conclusions: Five-millimeter isotropic margins for the SV constitute the minimum required to mitigate the intrafractional motion. Both the COM and the border are acceptable predictors for SV underdosage with 4.5- and 7.0-mm action threshold. Traditional margin based on the COM or border underestimates the margin.« less

Authors:
 [1];  [2];  [3];  [2];  [1]; ;  [1];  [2]
  1. Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina (United States)
  2. (United States)
  3. Medical Physics Graduate Program, Duke University, Durham, North Carolina (United States)
Publication Date:
OSTI Identifier:
22649946
Resource Type:
Journal Article
Resource Relation:
Journal Name: International Journal of Radiation Oncology, Biology and Physics; Journal Volume: 98; Journal Issue: 2; Other Information: Copyright (c) 2017 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; CENTER-OF-MASS SYSTEM; COMPUTERIZED TOMOGRAPHY; FIDUCIAL MARKERS; GROUND TRUTH MEASUREMENTS; PATIENTS; PROSTATE; RADIATION HAZARDS; RADIOTHERAPY

Citation Formats

Sheng, Yang, E-mail: Yang.Sheng@duke.edu, Medical Physics Graduate Program, Duke University, Durham, North Carolina, Li, Taoran, Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, Pennsylvania, Lee, W. Robert, Yin, Fang-Fang, Wu, Q. Jackie, and Medical Physics Graduate Program, Duke University, Durham, North Carolina. Exploring the Margin Recipe for Online Adaptive Radiation Therapy for Intermediate-Risk Prostate Cancer: An Intrafractional Seminal Vesicles Motion Analysis. United States: N. p., 2017. Web. doi:10.1016/J.IJROBP.2017.02.089.
Sheng, Yang, E-mail: Yang.Sheng@duke.edu, Medical Physics Graduate Program, Duke University, Durham, North Carolina, Li, Taoran, Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, Pennsylvania, Lee, W. Robert, Yin, Fang-Fang, Wu, Q. Jackie, & Medical Physics Graduate Program, Duke University, Durham, North Carolina. Exploring the Margin Recipe for Online Adaptive Radiation Therapy for Intermediate-Risk Prostate Cancer: An Intrafractional Seminal Vesicles Motion Analysis. United States. doi:10.1016/J.IJROBP.2017.02.089.
Sheng, Yang, E-mail: Yang.Sheng@duke.edu, Medical Physics Graduate Program, Duke University, Durham, North Carolina, Li, Taoran, Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, Pennsylvania, Lee, W. Robert, Yin, Fang-Fang, Wu, Q. Jackie, and Medical Physics Graduate Program, Duke University, Durham, North Carolina. 2017. "Exploring the Margin Recipe for Online Adaptive Radiation Therapy for Intermediate-Risk Prostate Cancer: An Intrafractional Seminal Vesicles Motion Analysis". United States. doi:10.1016/J.IJROBP.2017.02.089.
@article{osti_22649946,
title = {Exploring the Margin Recipe for Online Adaptive Radiation Therapy for Intermediate-Risk Prostate Cancer: An Intrafractional Seminal Vesicles Motion Analysis},
author = {Sheng, Yang, E-mail: Yang.Sheng@duke.edu and Medical Physics Graduate Program, Duke University, Durham, North Carolina and Li, Taoran and Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, Pennsylvania and Lee, W. Robert and Yin, Fang-Fang and Wu, Q. Jackie and Medical Physics Graduate Program, Duke University, Durham, North Carolina},
abstractNote = {Purpose: To provide a benchmark for seminal vesicle (SV) margin selection to account for intrafractional motion and to investigate the effectiveness of 2 motion surrogates in predicting intrafractional SV coverage. Methods and Materials: Fifteen prostate patients were studied. Each patient had 5 pairs (1 patient had 4 pairs) of pretreatment and posttreatment cone beam CTs (CBCTs). Each pair of CBCTs was registered on the basis of prostate fiducial markers. All pretreatment SVs were expanded with 1-, 2-, 3-, 4-, 5-, and 8-mm isotropic margins to form a series of planning target volumes, and their intrafractional coverage to the posttreatment SV determined the “ground truth” for exact coverage. Two motion surrogates, the center of mass (COM) and the border of contour, were evaluated by the use of Pearson product-moment correlation coefficient and exponential fitting for predicting SV underdosage. Action threshold of each surrogate was calculated. The margin for each surrogate was calculated according to a traditional margin recipe. Results: Ninety-five percent posttreatment SV coverage was achieved in 9%, 53%, 73%, 86%, 95%, and 97% of fractions with 1-, 2-, 3-, 4-, 5-, and 8-mm margins, respectively. The 5-mm margins provided 95% intrafractional SV coverage in over 90% of fractions. The correlation between the COM and border was weak, moderate, and strong in the left-right (L-R), anterior-posterior (A-P), and superior-inferior (S-I) directions, respectively. Exponential fitting gave the underdosage threshold of 4.5 and 7.0 mm for the COM and border. The Van Herk margin recipe recommended 0-, 0.5-, and 0.8-mm margins in the L-R, A-P, and S-I directions based on the COM, and 1.2-, 3.9-, and 2.5-mm margins based on the border. Conclusions: Five-millimeter isotropic margins for the SV constitute the minimum required to mitigate the intrafractional motion. Both the COM and the border are acceptable predictors for SV underdosage with 4.5- and 7.0-mm action threshold. Traditional margin based on the COM or border underestimates the margin.},
doi = {10.1016/J.IJROBP.2017.02.089},
journal = {International Journal of Radiation Oncology, Biology and Physics},
number = 2,
volume = 98,
place = {United States},
year = 2017,
month = 6
}
  • Purpose: To provide benchmark for seminal vesicles (SVs) margin selection to account for intra-fractional motion; and to investigate the effectiveness of two motion surrogates in predicting intra-fractional SV underdosage. Methods: 9 prostate SBRT patients were studied; each has five pairs of pre-treatment and post-treatment cone-beam CTs (CBCTs). Each pair of CBCTs was registered based on fiducial markers in the prostate. To provide “ground truth” for coverage evaluation, all pre-treatment SVs were expanded with isotropic margin of 1,2,3,5 and 8mm, and their overlap with post-treatment SVs were used to quantify intra-fractional coverage. Two commonly used motion surrogates, the center-of-mass (COM) andmore » the border of contour (the most distal points in SI/AP/LR directions) were evaluated using Receiver-Operating Characteristic (ROC) analyses for predicting SV underdosage due to intra-fractional motion. Action threshold of determining underdosage for each surrogate was calculated by selecting the optimal balancing between sensitivity and specificity. For comparison, margin for each surrogate was also calculated based on traditional margin recipe. Results: 90% post-treatment SV coverage can be achieved in 47%, 82%, 91%, 98% and 98% fractions for 1,2,3,5 and 8mm margins. 3mm margin ensured the 90% intra-fractional SV coverage in 90% fractions when prostate was aligned. The ROC analysis indicated the AUC for COM and border were 0.88 and 0.72. The underdosage threshold was 2.9mm for COM and 4.1mm for border. The Van Herk’s margin recipe recommended 0.5, 0 and 1.8mm margin in LR, AP and SI direction based on COM and for border, the corresponding margin was 2.1, 4.5 and 3mm. Conclusion: 3mm isotropic margin is the minimum required to mitigate the intra-fractional SV motion when prostate is aligned. ROC analysis reveals that both COM and border are acceptable predictors for SV underdosage with 2.9mm and 4.1mm action threshold. Traditional margin calculation is less reliable for this application. This work is partially supported a master research grant from Varian Medical Systems.« less
  • Purpose: For patients with intermediate- and high-risk prostate cancer, the seminal vesicles (SVs) are included in the clinical target volume (CTV). The purposes of this study are to investigate interfraction motion characteristics of the SVs and determine proper margins for online computed tomography image guidance. Methods and Materials: Twenty-four patients, each with 16 daily helical computed tomography scans, were included in this study. A binary image mask was used for image registration to determine daily organ motion. Two online image-guided radiotherapy strategies (prostate only and prostate + SVs) were simulated in a hypofractionated scheme. Three margin designs were studied formore » both three-dimensional conformal radiotherapy and intensity-modulated radiotherapy (IMRT). In prostate-only guidance, Margin A was uniformly applied to the whole CTV, and Margin B was applied to the SVs with a fixed 3-mm prostate margin. In prostate plus SV guidance, Margin C was uniformly applied to the CTV. The minimum margins were sought to satisfy the criterion that minimum cumulative CTV dose be more than those of the planning target volume in the plan for greater than 95% of patients. Results: The prostate and SVs move significantly more in the anterior-posterior and superior-inferior than right-left directions. The anterior-posterior motion of the prostate and SVs correlated (R{sup 2} = 0.7). The SVs move significantly more than the prostate. The minimum margins found were 2.5 mm for three-dimensional conformal radiotherapy and 4.5, 4.5, and 3.0 mm for Margins A, B, and C for IMRT, respectively. Margins for IMRT were larger, but the irradiated volume and doses to critical structures were smaller. Minimum margins of 4.5 mm to the SVs and 3 mm to the prostate are recommended for IMRT with prostate-only guidance. Conclusions: The SVs move independently from the prostate gland, and additional margins are necessary for image-guided radiotherapy.« less
  • Purpose: To investigate the choice of fixed margin or online adaptation when treating intermediate-risk prostate cancer including seminal vesicles (SV) using stereotactic body radiation therapy (SBRT). Methods: 9 prostate SBRT patients were retrospectively studied. All patients were implanted with fiducial markers in the prostate for daily localization and verification. Each patient had 5 pairs of pre-treatment and post-treatment cone-beam CT (CBCT) per protocol. SVs were contoured on planning CT and all CBCTs by one attending physician. Simultaneous integral boost (SIB) IMRT plans were developed to deliver 25Gy/5fx to the SV while delivering 37Gy/5fx to the prostate. A 3mm isotropic marginmore » was added to the prostate while a 5 mm isotropic margin was used for the SV. The planning CT was registered to daily pre-treatment and post-treatment CBCT based on fiducial markers in the prostate to mimic online prostate localization; and the SV on daily CBCT was transferred to the CT structure set after the prostates were aligned. Daily pre-treatment and post-treatment SV dose coverage and the organ-at-risk (OAR) sparing were evaluated for the SIB regimen. At least 95% of the SV need to receive the prescription dose (5Gy per fraction). Results: For the total of 90 daily SVs analyzed (ten CBCTs for each of nine patients), only 45 daily SVs (50%) were able to meet the coverage that 95% of the SV received 25Gy. The OAR sparing performance was acceptable for most of the dosimetric constraints in low-risk prostate SBRT protocol with only two exceptions in bladder V100 (cc). Conclusion: A fixed 5mm margin for SV is not sufficient to provide consistent daily dose coverage due to SV’s substantial inter- and intra-fractional motion relative to the prostate. This finding calls for innovative strategies in margin design as well as online treatment adaptation. This work is partially supported a master research grant from Varian Medical Systems.« less
  • Purpose: A clinical trial on stereotactic body radiation therapy (SBRT) for high-risk prostate cancer is undergoing at our institution. In addition to escalating dose to the prostate, we have increased dose to intra-prostatic lesions. Intra-fractional prostate motion deteriorates well planned radiation dose, especially for the small intra-prostatic lesions. To solve this problem, we have developed a motion tracking and 4D dose-reconstruction system to facilitate adaptive re-planning. Methods: Patients in the clinical trial were treated with VMAT using four arcs and 10 FFF beam. KV triggered x-ray projections were taken every 3 sec during delivery to acquire 2D projections of 3Dmore » anatomy at the direction orthogonal to the therapeutic beam. Each patient had three implanted prostate markers. Our developed system first determined 2D projection locations of these markers and then 3D prostate translation and rotation via 2D/3D registration of the markers. Using delivery log files, our GPU-based Monte Carlo tool (goMC) reconstructed dose corresponding to each triggered image. The calculated 4D dose distributions were further aggregated to yield the delivered dose. Results: We first tested each module in our system. MC dose engine were commissioned to our treatment planning system with dose difference of <0.5%. For motion tracking, 1789 kV projections from 7 patients were acquired. The 2D marker location error was <1 mm. For 3D motion tracking, root mean square (RMS) errors along LR, AP, and CC directions were 0.26mm, 0.36mm, and 0.01mm respectively in simulation studies and 1.99mm, 1.37mm, and 0.22mm in phantom studies. We also tested the entire system workflow. Our system was able to reconstruct delivered dose. Conclusion: We have developed a functional intra-fractional motion tracking and 4D dose re-construction system to support our clinical trial on adaptive high-risk prostate cancer SBRT. Comprehensive evaluations have shown the capability and accuracy of our system.« less
  • Purpose: Six months of androgen suppression therapy (AST) plus radiation (RT) prolongs survival vs. RT alone in men with unfavorable risk localized prostate cancer (PCa), but it is unknown if this benefit applies to all risk subgroups and, in particular, the intermediate-risk group. Methods and Materials: Among 206 men with stages T1b to T2b PCa and either a prostate-specific antigen level of >10 or a Gleason score of {>=}7 or MRI evidence of T3 disease randomized to receive 70 Gy of RT with or without 6 months of AST, Cox multivariable analysis was used to assess the impact of ASTmore » on overall survival in intermediate- and high-risk localized PCa, adjusting for age, Adult Comorbidity Evaluation 27 comorbidity score, interaction between comorbidity and treatment, and known prognostic factors. Survival estimates were compared using a two-sided log-rank test. Results: After an 8.2-year median follow-up, 74 men died. Compared to treatment with AST plus RT, treatment with RT alone was associated with an increased risk of death in intermediate-risk (adjusted hazard ratio, 3.0 [95% confidence interval, 1.3-7.2]; p = 0.01) and high-risk PCa (adjusted hazard ratio, 3.3 [95% confidence interval, 0.94-11.3]; p = 0.06). The survival benefit of adding AST was restricted to men with no or mild comorbidity in both the intermediate-risk (90.9% vs. 85.8% survival, respectively, at 7 years for AST plus RT vs. RT alone; p = 0.009) and high-risk (88.9% vs. 51.2% survival, respectively, at 7 years for AST plus RT vs. RT alone; p = 0.007) subgroups. Conclusions: In men with localized PCa who have no or mild comorbidity, adding 6 months of AST to RT was associated with improved survival for those with both intermediate-risk and high-risk disease, but in men with moderate to severe comorbidity, no benefit was observed in either risk group.« less