Advances in onboard, real-time imaging techniques are enabling a transformative shift in how to deliver targeted radiation therapies (RT). Alongside this, developments in functional and molecular imaging are driving an equally transformational paradigm shift in how to better understand the cancer target to be treated, as well as how tumors respond to targeted interventions. The personalization of treatment design and delivery based on near-real-time anatomical and biological imaging information necessitates adaptive processes that require robustness, accuracy, and speed.
MR-guided online geometric adaptation using MR-integrated treatment systems is achievable for most RT anatomic sites given MR’s high-quality imaging, flexibility in generating relative tissue contrasts and fast temporal acquisitions. Further developments are needed to assist the decision-making processes during online sessions, verify quality of the delivered treatments and proactively reinforce and/or refine clinical intent with each treatment fraction. We will discuss a fast procedure for the dose-of-the-day (DOTD) assessment of MR-based online adaptive RT in the context of MR-Linac, and methods for prospectively generating clinical goals (target and organs-at-risk) after each treatment fraction based on dose accumulation strategies driven by patient-specific deformable image registrations (DIR).
Biological adaptation is also being facilitated using a recently released biology-guided radiotherapy (BgRT) system. This system integrated a 6MVFFF ring gantry linac with a dual-arc PET imaging system and was designed to allow for a continuous response of the linac to the outgoing PET signals with radiation beams. Early experience with RT workflows and clinical adaptation will be discussed in conjunction with delivery accuracy testing to ultimately bring real time dose deposition based on metabolic and functional adaption closer to reality.
Finally, the increasing use of radiotherapy in multi-modality approaches together with targeted biological agents have emphasized the need for treatment response models encompassing the entire treatment, not only radiotherapy. Particularly when combining radiotherapy with immunotherapeutic approaches, there is now a focus on evaluating the effects of radiation on the patient’s immune response, in addition to the direct biological effects of radiation on the tumor. We will highlight current approaches in how to model the impact of radiotherapy on the immune system, studies investigating the role of fractionation and dose rate, and what role proton therapy and other advanced delivery modalities could play for immune-sparing radiotherapy regimen.
1. Understand the role of molecular imaging in quantifying the tumor microenvironment
2. Understand the RT workflows and challenges of MR-guided online adaptive treatments
3. Understand strategies for MR-driven dose accumulation and verification in MR-Linac systems.
4. Understand the key technology aspects of integrated PET-linac technology
5. Understand the state of the art and future perspectives of biologically-guided radiotherapy
6. Understand the role of biomathematical models to study combination treatment approaches
Funding Support, Disclosures, and Conflict of Interest: Dr. Cai reports grant funding from RefleXion Medical
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