ADAPTNOW: High-Precision Cancer Treatment by Online Adaptive Proton Therapy

A highly promising approach for the treatment of cancer is intensity-modulated proton therapy (IMPT), which is a new and most advanced form of proton therapy. The use of protons to irradiate a tumor has distinct advantages over using photons. A high-energy proton beam in first instance deposits a only small dose when it enters the patient’s body. The absorbed dose increases gradually with increasing depth and rises to a greatly localized dose peak in the tumor. This peak is known as the Bragg peak. IMPT thus has a unique potential to spare healthy tissues. However, the highly localized dose deposition makes proton therapy and IMPT in particular, very sensitive to the daily variations in the patient’s anatomy that are often observed as a result of e.g. organ motion, patient alignment errors, and/or tumor regression. These variations may, if not adequately dealt with, cause a severe overdose to healthy tissues and/or an underdose in the tumor.

With the recent introduction of proton therapy in the Netherlands, it is timely to develop novel image-guided and adaptive treatment strategies that mitigate the aforementioned limitations and that fully exploit the superior physical properties of protons compared to photons. In the ADAPTNOW project we are developing new methods to depict the internal anatomy just before each daily treatment, to rapidly adapt the treatment plan to compensate for any observed variations, and to verify the delivered dose while performing the irradiation. This online-adaptive treatment strategy will make use of unique image-guidance systems available in the Holland Particle Therapy Centre (HollandPTC), such as an in-room CT scanner that shares its patient table with the proton therapy equipment and instruments to determine the Bragg peak position in-vivo by imaging the prompt gamma (PG) radiation produced by the protons.

ADAPTNOW thus aims to develop highly-automated and cost-efficient, image-guided daily dose-adaptation and in-vivo QA procedures. This will allow for more accurate targeting of the tumor while reducing the dose to healthy tissues, so as to reduce complications and improve quality of life.

ADAPTNOW is a Medical Delta collaboration that brings together the expertise of Delft University of Technology, Erasmus Medical Center, Leiden University Medical Center, the Holland Particle Therapy Centre, and industry. The lead researchers are Dr. Mischa Hoogeman (Erasmus MC Cancer Institute), Dr. Marius Staring (LUMC), and Dr. Dennis Schaart (TU Delft). The project is partly funded by ZonMw.