Product Development of Intensity Modulation for Bolus Electron Conformal Therapy

Project Summary/Abstract Objective: This project aims to elevate electron beam therapy (EBT) technology, which provides effective radiation treatment for superficial cancers (depthandlt;6 cm), to that of other external beam radiotherapies (XRT), e.g. x-rays and protons, by bringing electron intensity modulation into the clinic. Challenge: Approximately 10% of radiotherapy patients (173,000 in USA annually) receive EBT for a portion of their treatment, and as many as 10% of these (17,300 annually) might benefit from bolus electron conformal therapy (BECT), which conforms the distal 90% dose surface to the cancerous planning target volume (PTV), protecting adjacent healthy tissue. Currently, radiation oncologists are limited in using BECT because PTV dose spread can be as great as 30% due to irregular bolus surface. This can be reduced to 10% by spatially modulating incident electron beam intensity. Heretofore, electron intensity modulation delivery technology has been unavailable. Innovation: Using our research collaborator’s recently invented electron intensity modulator design, Phase I demonstrated proof-of-principle for a PRIME (Passive Radiotherapy Intensity Modulator for Electrons), a low cost technology for which .decimal developed a fabrication method. PRIME consists of a matrix of small- diameter, cylindrical tungsten island blocks imbedded in a low-density foam in the beam-defining, collimating aperture. Varying diameters of island blocks placed on a hexagonal grid achieves desired intensity modulation. However, because current treatment planning systems (TPS) cannot manage PRIMEs, an electron TPS needs to be developed as well. Research Design: Phase II specific aims include (1) refining the pencil beam redefinition algorithm used for dose calculation under island blocks, (2) creating and evaluating an electron specific TPS, COMET-Plan (Computer Optimized andamp; Modulated Electron Therapy Planning), which plans intensity modulated bolus electron conformal therapy (IM-BECT) and conventional EBT, managing treatment aids such as skin collimators and eye shields, (3) developing factory and clinical PRIME quality assurance methods, (4) performing a multi-institutional treatment planning study to determine the degree to which IM-BECT improves BECT dose plans, and (5) validating IM-BECT planning and delivery by comparing doses measured in anthropomorphic phantoms with planned (calculated) doses. Health Benefit: PRIME devices and COMET-Plan software will allow a new technique, IM-BECT, which provides uniform dose conforming to the PTV, resulting in (1) equally high chance of cancer control, (2) equally or better low chance of acute normal tissue complications, and (3) decreased chance of secondary cancers. For some patients, this will provide a better dose distribution than other XRT modalities, such as volumetric arc therapy or helical tomotherapy, improving their cancer treatment. Commercialization: As the world’s leading company producing patient-specific radiotherapy devices we are well equipped for bringing PRIME intensity modulators and COMET-Plan software to radiotherapy clinics, supporting the exciting, new IM-BECT.Project Narrative Electron beam therapy (EBT), an effective modality for radiotherapy of superficial (depth ≤6 cm) cancers (173,000 potential US patients/year), has the ability to protect distal healthy tissue from acute and long- term adverse effects of radiation; however, radiation oncologists are often limited in use of its most powerful delivery technique, bolus electron conformal therapy (BECT), because of excessive dose heterogeneity (as great as 30%) in the targeted cancer volume due to the irregular proximal surface of the bolus. This SBIR Phase II application proposes to complete research and development of an intensity modulation technology (delivery device and planning software) that can be integrated with existing bolus ECT technology, previously shown to provide a more uniform (10%) and equally conformal dose distribution to the targeted cancer volume. Heretofore, no such product has been available; therefore, if developed, this will (1) offer a new modality, intensity modulated BECT (IM-BECT) technique, (2) open the pathway for further electron intensity modulated radiotherapy research, and (3) improve all EBT via a new, electron-specific treatment planning system that properly manages treatment aids, all three greatly improving current electron radiotherapy technology and potentially providing an improved alternative to other radiation modalities by having decreased chance of secondary cancers, equally high chance of cancer control, and equally low chance of acute normal tissue complications.