Case Study | June 04, 2015 | Sponsored by RaySearch Laboratories

Advanced Planning for Accurate Proton Treatments at the Provision Center for Proton Therapy

RayStation Treatment Planning System provides required technologies to deliver high quality plans

Original treatment plan

Figure 1: Original treatment plan

Final adapted plan

Figure 2: Final adapted plan

Three field robust plan

Figure 3: Three field robust plan

DVH for final robust plan

Figure 4: DVH for final robust plan

Proton therapy is an exciting modality in radiation oncology. It is the target of both positive and negative perspectives - the positive related to the technology itself and the ability of proton beams to deposit energy mostly within the tumor being treated. The negative opinions generally result from the historically high cost to build and maintain a center and the lack of access for patients worldwide. The Provision Center for Proton Therapy has not only embraced proton therapy, but also the concept that it must be used in conjunction with other advanced technologies that will assure treatment accuracy. 

Because proton beams are so controllable, it is important to recognize that a treatment can accurately miss a cancerous tumor if the treatment is not planned and monitored carefully. In the case of conventional photon treatment courses, dosimetric errors are not as likely to occur, and corrections are relatively easy to make. With protons, minor variations in patient shape and density, along with positioning error, can result in very significant differences in delivering the planned dose.

To this end the center has very successfully implemented two key technologies with its treatment planning system - robust optimization and adaptive therapy. RayStation from RaySearch Laboratories allows staff to create very advanced plans quickly and efficiently.

Adaptive Planning

The first example demonstrates how important it can be to modify plans based on changes during treatment. A woman presented with a right breast cancer that was very large and invasive. It was expected that the patient would have a fast response so weekly QA CTs were performed during treatment. Deformable registration was used to determine if the existing plan had adequate coverage. Soon after the treatment commenced, the scans showed significant changes that warranted replanning. The center used the adaptive planning function in RayStation to quickly replan the case and get back to the prescribed dose. The adaptive planning function does not require that the user re-enter the beam parameters or the inverse planning objectives. In total four adapted plans were implemented over the course of treatment with only a day or so needed each time to complete the planning and quality assurance. The sum of the doses was easily displayed so that an overall analysis could be made on the efficacy of the delivery. Adaptive planning in a case like this is simply unavoidable - in the case of protons that are sensitive to density and anatomical changes in the body, it would be impossible to plan this in an efficient and/or safe manner without advanced technologies such as deformable registration and adaptive therapy.

Robust Optimization

Protons are very sensitive to changes in density and patient shape.
Therefore, variations in patient positioning can have dramatic effects on the dose distribution. The use of planning target volumes (PTVs) to account for these variations is not always sufficient to achieve a robust plan. To enable the creation of robust plans for cases, where conventional margins do not work, RayStation implements, instead, robust optimization, which explicitly takes these variations into account and aims for a plan that is as good as possible with respect to the worst case variation.

The patient in a second clinical case (Figures 3 and 4) had a clinical target volume (CTV) that was anterior on the sternum but also a CTV in the mediastinum behind the great vessels. A plan was designed to treat the anterior CTV with an AP beam and the posterior CTV with posterior obliques. However, the lung interface and the fact that the CTVs overlapped superior/inferior presented a challenge. Instead of treating single field uniform dose (SFUD) and irradiating more lung and heart tissue, robust optimization was utilized. This allowed the team to account for range uncertainty in a very heterogeneous area, and ensure that with setup error and range uncertainty there would be no unacceptable hot or cold spots. Uniform dose was achieved in a robust manner, even where the CTVs overlapped. Robust optimization further eliminated the need for beam specific PTVs and a complicated optimization process.

Proton therapy requires a very high level of focus and treatment planning technology. Intensity modulated proton therapy (IMPT) in RayStation allows for quick, efficient, robust and adaptive planning for effective proton treatments.

Case study supplied by RaySearch Laboratories.

Related Content

Treating lung cancer patients with proton therapy may help reduce the risk of radiation-induced heart diseases, suggests a new study from Penn Medicine. In a retrospective trial of more than 200 patients, mini-strokes were significantly less common among patients who underwent proton therapy versus conventional photon-based radiation therapy. Proton therapy patients also experienced fewer heart attacks.
News | Proton Therapy | October 25, 2020
October 25, 2020 — Treating lung cancer patients with prot...
Be sure to register for the American Society for Radiation Oncology's (ASTRO) 62nd Annual Meeting, to be held October 24-28, 2020, via an interactive virtual platform. The meeting, Global Oncology: Radiation Therapy in a Changing World, will feature reports from the latest clinical trials; panels on global oncology, health disparities and the novel coronavirus; and an immersive attendee experience in a virtual convention center.
News | ASTRO | October 23, 2020
October 23, 2020 — Be sure to ...
IBA showcases how its Proteus solutions and its network of clinical and industrial partners are shaping the future of proton therapy
News | Proton Therapy | October 23, 2020
October 23, 2020 — IBA, a leading provider of proton thera...
RaySearch Laboratories AB will demo its latest advances in oncology software at the American Society for Radiation Oncology (ASTRO) 2020 Annual Meeting
News | Radiation Oncology | October 23, 2020
October 23, 2020 — RaySearch will present recent and upcoming enhancements, as well as new functionality, in...
Mevion Medical Systems announced that it has shipped the accelerator module for the Mevion S250i Proton Therapy System to Kunshan, China. The 15-ton compact accelerator, the heart of the proton therapy system, is the smallest of its kind and will be the first in China.

Mevion's compact accelerator module is lifted and placed on a truck for the first leg of its journey to China. (Photo: Business Wire)

News | Proton Therapy | October 16, 2020
October 16, 2020 — Mevion Medical Systems announced that it has shipped the accelerator module for the...
Important milestone demonstrates the unrivalled experience, technological innovation and global market leadership of IBA and its clinical partners
News | Proton Therapy | September 25, 2020
September 25, 2020 — IBA (Ion Beam Applications SA) announced that more than 100,000 patients have now been treated w
Varian Drives Next Evolution of Proton Treatment Planning with Eclipse v16.1
News | Treatment Planning | September 15, 2020
September 15, 2020 — Varian announced it has received FDA 510(k) clearance for its Eclipse v16.1 treatment planning s
Proton therapy has evolved, and future predictions include smaller systems, more sophisticated proton dosimetry and devices that manipulate the proton beam
Feature | Proton Therapy | July 06, 2020 | By Minesh Mehta, M.D.
The field of proton...
News | Proton Therapy | June 16, 2020
June 17, 2020 — RaySearch Laboratories AB launched the latest release of its widely adopted treatment planning system