Paul G. Archer

Indications, Integration, and Technical Aspects of Local-Regional Irradiation in the Management of Advanced Breast Cancer

This article reviews the indications for radiotherapy in advanced stage disease and discusses the recent prospective trials demonstrating a survival benefit by the addition of radiotherapy. Various treatment plans are reviewed with and without internal mammary node coverage. Although it is not clear whether internal mammary node irradiation can have a favorable impact on survival, it is clear that inadequate treatment planning of the parasternal region can result in excess cardiac morbidity and mortality. Careful planning using computed tomographic systems is required to optimize chest wall planning. With individualized treatment planning, it is hoped that the next generation of trials will show improved survival from further reduction in breast cancer deaths and significantly decreased cardiac toxicity.

Clinical Use of a Mutual Information-Based Automated Image Registration System for Conformal Radiotherapy Treatment Planning

In this paper we describe the clinical use of an in-house mutual information-based image registration system for improving target volume definition in conformal radiotherapy treatment planning. This system enables a clinician to delineate clinical and anatomic structures on magnetic resonance and nuclear medicine imaging studies and have these structures geometrically mapped to the x-ray CT study used for treatment planning. This system requires very little user interaction and can accommodate a wide range of anatomic sites. These factors combined with consistent accuracy at the sub-voxel to voxel level have improved the overall quality and physician confidence in the delineation of target volumes and surrounding healthy tissues.

Knowledge-based treatment planning and its potential role in the transition between treatment planning systems

Commissioning a new treatment planning system (TPS) involves many time-consuming tasks. We investigated the role that knowledge-based planning (KBP) can play in aiding a clinics transition to a new TPS. Sixty clinically treated prostate/prostate bed intensity-modulated radiation therapy (IMRT) plans were exported from an in-house TPS and were used to create a KBP model in a newly implemented commercial application. To determine the benefit that KBP may have in a TPS transition, the model was tested on 2 groups of patients. Group 1 consisted of the first 10 prostate/prostate bed patients treated in the commercial TPS after the transition from the in-house TPS. Group 2 consisted of 10 patients planned in the commercial TPS after 8 months of clinical use. The KBP-generated plan was compared with the clinically used plan in terms of plan quality (ability to meet planning objectives and overall dose metrics) and planning efficiency (time required to generate clinically acceptable plans). The KBP-generated plans provided a significantly improved target coverage (p = 0.01) compared with the clinically used plans for Group 1, but yielded plans of comparable target coverage to the clinically used plans for Group 2. For the organs at risk, the KBP-generated plans produced lower doses, on average, for every normal-tissue objective except for the maximum dose to 0.1 cc of rectum. The time needed for the KBP-generated plans ranged from 6 to 15 minutes compared to 30 to 150 and 15 to 60 minutes for manual planning in Groups 1 and 2, respectively. KBP is a promising tool to aid in the transition to a new TPS. Our study indicates that high-quality treatment plans could have been generated in the newly implemented TPS more efficiently compared with not using KBP. Even after 8 months of the clinical use, KBP still showed an increase in plan quality and planning efficiency compared with manual planning.

SU-G-TeP4-14: Quality Control of Treatment Planning Using Knowledge-Based Planning Across a System of Radiation Oncology Practices

PURPOSE There is potentially a wide variation in plan quality for a certain disease site, even for clinics located in the same system of hospitals. We have used a prostate-specific knowledge-based planning (KBP) model as a quality control tool to investigate the variation in prostate treatment planning across a network of affiliated radiation oncology departments. METHODS A previously created KBP model was applied to 10 patients each from 4 community-based clinics (Clinics A, B, C, and D). The KBP model was developed using RapidPlan (Eclipse v13.5, Varian Medical Systems) from 60 prostate/prostate bed IMRT plans that were originally planned using an in-house treatment planning system at the central institution of the community-based clinics. The dosimetric plan quality (target coverage and normal-tissue sparing) of each model-generated plan was compared to the respective clinically-used plan. Each community-based clinic utilized the same planning goals to develop the clinically-used plans that were used at the main institution. RESULTS Across all 4 clinics, the model-generated plans decreased the mean dose to the rectum by varying amounts (on average, 12.5, 2.6, 4.5, and 2.7 Gy for Clinics A, B, C, and D, respectively). The mean dose to the bladder also decreased with the model-generated plans (5.4, 2.3, 3.0, and 4.1 Gy, respectively). The KBP model also identified that target coverage (D95%) improvements were possible for for Clinics A, B, and D (0.12, 1.65, and 2.75%) while target coverage decreased by 0.72% for Clinic C, demonstrating potentially different trade-offs made in clinical plans at different institutions. CONCLUSION Quality control of dosimetric plan quality across a system of radiation oncology practices is possible with knowledge-based planning. By using a quality KBP model, smaller community-based clinics can potentially identify the areas of their treatment plans that may be improved, whether it be in normal-tissue sparing or improved target coverage. M. Matuszak has research funding for KBP from Varian Medical Systems.

SU-E-T-530: Knowledge-Based Treatment Planning and Its Potential Role in the Transition Between Treatment Planning Systems

Purpose: Commissioning a treatment planning system (TPS) involves many tasks, including making sure users have sufficient training and experience to create quality plans. We investigated the role that knowledge-based planning (KBP) can play in aiding a clinic’s transition to a new TPS. Methods: 60 clinically treated prostate and prostate bed IMRT plans were exported from an in-house TPS and used to create a KBP-model in a newly introduced commercial TPS (Eclipse v13.5, Varian Medical Systems). To determine the benefit that KBP may have in a TPS transition, the model was tested on two groups. Group 1 consisted of the first 10 patients treated in the commercial TPS after the transition from the in-house TPS, Group 2 consisted of 10 patients planned in the commercial TPS, but without the KBP model, after 8 months of clinical use. The KBP-generated plan for each patient was compared to the clinically-used plan in terms of quality and planning efficiency. Results: On average, the KBP-generated plans provided better target coverage for group 1 than the clinical plans,and about equivalent coverage for group 2. The average absolute difference (KBP-clinical) for D95 for the PTV was 0.48±0.49% and −0.11±0.48% for groups 1 and 2, respectively. For the OARs, the KBP-generated plans produced lower doses for every normal tissue objective except the maximum dose to 0.1cc of rectum (0.50±0.27Gy and 0.22±0.17Gy for groups 1 and 2, respectively). The time needed for KBP-generated plans ranged from 6– 15min compared to 30–150 and 15–60min for groups 1 and 2, respectively. Conclusion: Knowledge-based planning is a promising tool to aid in transitions to new TPSs. Our study indicates that high-quality treatment plans could have been generated in the new TPS more efficiently compared to not using KBP. Even after 8 months of clinical use, KBP still showed a quality and efficiency increase compared to manual planning. Partially supported by Varian Medical Systems