Prof. Zelig A. Tochner is Professor of Radiation Oncology at the National University of Singapore.

Recently, a breakthrough solution to enable the expansion of proton therapy without the need to build a separate proton center, a new and significantly less costly paradigm becomes available.

Tel Aviv, Israel (PRWEB)
August 30, 2022

Despite the proven and potential clinical benefits of proton therapy, this treatment is currently available to very few patients. The reasons are primarily economic. Until now, the equipment size required its own dedicated building. Combining construction and heavy equipment cost severely limited the potential for cost-effective operation and ROI in a reasonable period. Previously, the dimension of proton therapy equipment – accelerator, beam delivery, treatment planning and delivery room — did not allow for integration of the equipment within existing radiotherapy practice facilities. Because of the constraints of legacy equipment and design, combined with the substantial cost to develop, build and operate a stand-alone proton center, the expansion of proton treatment to existing radiotherapy centers, and to physician-owned centers, has been extremely limited.

Despite all of the above, due to the clinical benefits demonstrated since 1954, proton therapy has become a significant tool to fight cancer with radiation. Today, there are over 130 proton centers worldwide. Recently, a breakthrough solution to enable the expansion of proton therapy without the need to build a separate proton center, a new and significantly less costly paradigm becomes available. Proton therapy can now be centered in an existing linac vault. To do so, there are five requirements to allow healthcare provider to integrate proton therapy into an operating radiotherapy department, while eliminating the barriers of installing and operating existing legacy proton therapy systems.

Requirement 1. Use of a synchrotron to produce the proton beam.

A synchrotron is a type of proton accelerator which does produces significantly less neutron radiation during operation when compared with industry standard cyclotrons. Due to this accelerator advantage, a synchrotron can be safely placed together with image guided patient positioning equipment within the treatment vault, exactly as it is being done today with conventional radiotherapy linacs. This differs from the current practice of installing a proton accelerator in a separately shielded bunker. The current practice stems from the use of legacy cyclotron accelerators which produce harmful neutrons during operation.

Additionally, the current generation of synchrotrons may be installed and operated within a very limited space (comparable to a modern photon linac treatment vault). Further, unlike the cyclotron design, synchrotrons are modular, permitting individual component parts to be delivered (via regular elevators) and installed within an existing linac room. Even modern compact cyclotron design still prevents installation without significant construction effort due to size and weight of the single component (in addition to construction of the required additional dedicated shielded vault exclusively for the accelerator).

Requirement 2. Gantry-less pencil beam scanning (PBS) delivery system. The PBS allows for delivering the treatment dose by an intensity modulated technique ensuring high treatment quality in accordance with the prescribed treatment plan objectives and constrains. Beam delivery without the use of a rotating gantry significantly reduces the equipment dimension, making installation of a proton machine in a linac vault feasible. The gantry-less solution allows for treatment delivery to all anatomical sites and offers the benefits of upright/seated position for both treatment planning and delivery. The seated position reduces body motion allowing for more precise beam delivery—less organ motion means more accurate treatment. A clinical study that is currently planned by the Hadassah Medical Center in Israel should provide comprehensive information about the protocols for delivering proton therapy to various anatomical sites of patients treated in a seated orientation.

Requirement 3. Image guided positioning for patients in a seated position. The seated position enables delivering the treatment beam from all directions to meet optimal treatment planning requirements. This paradigm shifting solution includes both the patient support and the imaging equipment. This solution allows for patient treatment in multiple seated positions, providing flexibility to enable access to all anatomical areas during imaging and treatment. The patient support should be mounted on a robotic arm. The arm provides 6 degrees of freedom permitting correction should changes to the tumor site are necessary. The proper patient positioning is ensured by imaging of internal organs. The 2D imaging is based on a specially oriented pair of x-ray systems that should be integrated into the walls or floor of the treatment room. The orientation of the x-ray system allows imaging of patients along the perpendicular or longitudinal axes of the patient’s body. In addition to the x-ray systems, 3D and 4D imaging can also be carried out using an in-room CT modality – a specially designed CT scanner that can image the patient in a seated position. During image acquisition the scanner moves while the patient stays fixed in the seated position. The 4D CT acquires patient images of a diagnostic quality for two reasons: (1) to define correctness of the patient position and (2) to monitor the treatment site during the course of treatment and (3) to enable adaptive therapy when needed.

Requirement 4. CT simulation of patients in a seated position. The radiation therapy golden rule is to plan the treatment and treat in the same patient position. This requires having a vertical 4D CT scanner for scanning seated patients. The CT simulator, preferably, should be the same scanner that is used for image guided positioning. However, a vertical CT simulator can also be installed outside the treatment vault. The latter point is an option in order not to always use the treatment room for simulation, enabling higher patient treatment throughput. Although, several academic clinical institutions have installed “home-made” vertical scanner, the only company that developed an FDA cleared and CE marked vertical CT scanner is P-Cure.

Requirement 5. Treatment planning software (TPS) that “understands” that the patient is treated in a seated orientation. Although there are some ways to avoid this requirement, to generate treatment plans with TPS that has not integrated a chair model is challenging. To streamline the treatment planning process, one must use TPS that has been integrated into the seated treatment concept. Raysearch, the leading provider of treatment planning solutions, has already implemented a software module for planning treatments in a seated orientation. More companies will follow the trend.

If proton therapy is meant to become part of the mainstream clinical practice, no doubt there will be more and more solutions that match the criteria I have described above.

About the Author:

Prof. Zelig A. Tochner is Professor of Radiation Oncology at the National University of Singapore. A Professor Emeritus and the former medical director of the Roberts Proton Therapy Center at the University of Pennsylvania Medical Center, one of the world’s largest proton therapy facilities. He was also the chief of the Pediatric Radiation Oncology service for the Children’s Hospital of Philadelphia.

Prof. Tochner received his MD from the Hebrew University-Hadassah Medical School and is board certified in Radiation and Medical Oncology. He was recognized by Best Doctors in America 2005-2006, 2009-2010, 2011-2012. Contact at zelig.touchner@gmail.com

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