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Evaluation of complexity and deliverability of prostate cancer treatment plans designed with a knowledge-based VMAT planning technique.

ABSTRACT: PURPOSE:Knowledge-based planning (KBP) techniques have been reported to improve plan quality, efficiency, and consistency in radiation therapy. However, plan complexity and deliverability have not been addressed previously for treatment plans guided by an established in-house KBP system. The purpose of this work was to assess dosimetric, mechanical, and delivery properties of plans designed with a common KBP method for prostate cases treated via volumetric modulated arc therapy (VMAT). METHODS:Thirty-one prostate patients previously treated with VMAT were replanned with an in-house KBP method based on the overlap volume histogram. VMAT plan complexities of the KBP plans and the reference clinical plans were quantified via monitor units, modulation complexity scores, the edge metric, and average leaf motion per degree of gantry rotation. Each set of plans was delivered to the same diode array and agreement between computed and measured dose distributions was evaluated using the gamma index. Varying percent dose-difference (1-3%) and distance-to-agreement (1 mm to 3 mm) thresholds were assessed for gamma analyses. RESULTS:Knowledge-based planning (KBP) plans achieved average reductions of 6.4 Gy (P < 0.001) and 8.2 Gy (P < 0.001) in mean bladder and rectum dose compared to reference plans, while maintaining clinically acceptable target dose. However, KBP plans were significantly more complex than reference plans in each evaluated metric (P < 0.001). KBP plans also showed significant reductions (P < 0.05) in gamma passing rates at each evaluated criterion compared to reference plans. CONCLUSIONS:While KBP plans had significantly reduced bladder and rectum dose, they were significantly more complex and had significantly worse quality assurance outcomes than reference plans. These results suggest caution should be taken when implementing an in-house KBP technique.

SUBMITTER: Wall PDH

PROVIDER: S-EPMC6964749 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Evaluation of complexity and deliverability of prostate cancer treatment plans designed with a knowledge-based VMAT planning technique.

Wall Phillip D H PDH Fontenot Jonas D JD

Journal of applied clinical medical physics 20191209 1

<h4>Purpose</h4>Knowledge-based planning (KBP) techniques have been reported to improve plan quality, efficiency, and consistency in radiation therapy. However, plan complexity and deliverability have not been addressed previously for treatment plans guided by an established in-house KBP system. The purpose of this work was to assess dosimetric, mechanical, and delivery properties of plans designed with a common KBP method for prostate cases treated via volumetric modulated arc therapy (VMAT).<h ...[more]

PMID: 31816175

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Project description:BACKGROUND: The newest release of the Eclipse (Varian) treatment planning system (TPS) includes an optimizing engine for Elekta volumetric-modulated arc therapy (VMAT) planning. The purpose of this study was to evaluate this new algorithm and to compare it to intensity-modulated radiation therapy (IMRT) for various disease sites by creating single- and double-arc VMAT plans. METHODS: A total of 162 plans were evaluated in this study, including 38 endometrial, 57 head and neck, 12 brain, 10 breast and 45 prostate cancer cases. The real-life IMRT plans were developed during routine clinical cases using the TPS Eclipse. VMAT plans were generated using a preclinical version of Eclipse with tumor-region-specific optimizing templates without interference of the operator: with one full arc (1A) and with two full arcs (2A), and with partial arcs for breast and prostate with hip implant cases. All plans were evaluated based on target coverage, homogeneity and conformity. The organs at risk (OARs) were analyzed according to plan objectives, such as the mean and maximum doses. If one or more objectives were exceeded, the plan was considered clinically unacceptable, and a second VMAT plan was created by adapting the optimization penalties once. RESULTS: Compared to IMRT, single- and double-arc VMAT plans showed comparable or better results concerning the target coverage: the maximum dose in the target for 1A is the same as that for IMRT; for 2A, an average reduction of 1.3% over all plans was observed. The conformity showed a statistically significant improvement for both 1A (+3%) and 2A (+6%). The mean total body dose was statistically significant lower for the considered arc techniques (IMRT: 16.0?Gy, VMAT: 15.3?Gy, p?<?0.001). However, the sparing of OARs shows individual behavior that depends strongly on the different tumor regions. A clear difference is found in the number of monitor units (MUs) per plan: VMAT shows a reduction of 31%. CONCLUSION: These findings demonstrate that based on optimizing templates with minimal interaction of the operator, the Eclipse TPS is able to achieve a plan quality for the Elekta VMAT delivery technique that is comparable to that of fixed-field IMRT. Plans with two arcs show better dose distributions than plans with one arc.

Project description:Postoperative/adjuvant radiotherapy of advanced gastric cancer involves a large planning target volume (PTV) with multi-concave shapes which presents a challenge for volumetric modulated arc therapy (VMAT) planning. This study investigates the advantages of automated VMAT planning for this site compared to manual VMAT planning by expert planners.For 20 gastric cancer patients in the postoperative/adjuvant setting, dual-arc VMAT plans were generated using fully automated multi-criterial treatment planning (autoVMAT), and compared to manually generated VMAT plans (manVMAT). Both automated and manual plans were created to deliver a median dose of 45 Gy to the PTV using identical planning and segmentation parameters. Plans were evaluated by two expert radiation oncologists for clinical acceptability. AutoVMAT and manVMAT plans were also compared based on dose-volume histogram (DVH) and predicted normal tissue complication probability (NTCP) analysis.Both manVMAT and autoVMAT plans were considered clinically acceptable. Target coverage was similar (manVMAT: 96.6?±?1.6%, autoVMAT: 97.4?±?1.0%, p?=?0.085). With autoVMAT, median kidney dose was reduced on average by >?25%; (for left kidney from 11.3?±?2.1 Gy to 8.9?±?3.5 Gy (p?=?0.002); for right kidney from 9.2?±?2.2 Gy to 6.1?±?1.3 Gy (p?<? 0.001)). Median dose to the liver was lower as well (18.8?±?2.3 Gy vs. 17.1?±?3.6 Gy, p?=?0.048). In addition, Dmax of the spinal cord was significantly reduced (38.3?±?3.7 Gy vs. 31.6?±?2.6 Gy, p?<? 0.001). Substantial improvements in dose conformity and integral dose were achieved with autoVMAT plans (4.2% and 9.1%, respectively; p?<? 0.001). Due to the better OAR sparing in the autoVMAT plans compared to manVMAT plans, the predicted NTCPs for the left and right kidney and the liver-PTV were significantly reduced by 11.3%, 12.8%, 7%, respectively (p???0.001). Delivery time and total number of monitor units were increased in autoVMAT plans (from 168?±?19 s to 207?±?26 s, p?=?0.006) and (from 781?±?168 MU to 1001?±?134 MU, p?=?0.003), respectively.For postoperative/adjuvant radiotherapy of advanced gastric cancer, involving a complex target shape, automated VMAT planning is feasible and can substantially reduce the dose to the kidneys and the liver, without compromising the target dose delivery.

Dataset Information

Evaluation of complexity and deliverability of prostate cancer treatment plans designed with a knowledge-based VMAT planning technique.

Publications

Evaluation of complexity and deliverability of prostate cancer treatment plans designed with a knowledge-based VMAT planning technique.

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