UCLA Journal of Radiation Oncology SPRING 2024 - Flipbook - Page 40
UCLA RADIATION ONCOLOGY JOURNAL
Also crucial to this discussion of incorporating MRgRT into the standard of care in radiation oncology
is the realization that the process of care for MRI-based radiation therapy, particularly MRI adaptive
radiation therapy, is fundamentally a very different radiation treatment delivery process than that
currently utilized for CT-based radiation therapy. The ability for on-table adaptive planning and
re-planning with MRgRT represents the most unique aspects of this technology.88 While adaptive
radiation treatment is not a new concept in radiation oncology,89 it historically has been limited due
to the logistics of CTgRT. Specifically, legacy approaches to adaptive radiation therapy have not been
performed on-table in real-time.50 Instead, they are done off-line prior to the next treatment, and
they cannot address target or organ at risk deformation. MRgRT, in contrast, allows for a feasible and
superior mechanism for performing adaptive radiation therapy, specifically while the patient is on
the treatment table, and can be repeated daily. While the data supporting adaptive radiation therapy
continue to accumulate, our field must remain open to the plasticity that may accompany the radical
shifts in the process of care that MRgRT affords.
Peering into the future, one might imagine a treatment process where simulation as we have come
to know it is not performed at all, and treatment is simply delivered de novo based on the daily
anatomy. A simulation-free radiation treatment process has been explored in palliative cases, though
this process relied on diagnostic images for planning.90 In the future, we might be able to rely on
treatment machine-generated MRI images alone. These images will require adequate soft-tissue
contrast during the on-table acquisition period, which is currently under evaluation.91 Omission of
traditional simulation scans might thus represent a potential avenue to enhance accuracy and quality
of care, particularly from the patient perspective as this would reduce appointments, costs, and time
from consult to treatment, which might be of particular benefit for patients experiencing symptoms
from their tumor such as pain or bleeding.reduction in dose delivered to organs at risk. Beyond the
standard anatomic considerations at the time of treatment planning, MRI simulation also unlocks
functional tumor-specific considerations as well, which can be interrogated with MRI-based functional
imaging, as noted previously. Given the rapidly increased use of MRI-simulation in recent years, the
American Association of Physicists in Medicine (AAPM) have published a task group report providing
recommendations on the safe and optimal use of MRI simulation,87 which is a key aspect of the
structure component in the value framework described above. These advantages, as well as the more
complicated process of care, validate the notion that MRI-only simulation should not just be conflated
with standard simulation nomenclature. Instead, its work and practice expense should be valued for
what are already established equipment costs and process of care differences.
Conclusion
MRgRT has already disrupted the process of care as it pertains to radiation treatment delivery and
is well on its way to disrupting the current process of care as it pertains to simulation and treatment
planning. With disruption comes new opportunities to evaluate value. While key randomized and nonrandomized prospective studies have begun to support the value of MRgRT, this work will be further
supplemented by formal cost-effectiveness analyses as more and more robust toxicity and efficacy
data emerge. In addition, many prospective clinical trials are currently underway or in development.
Ultimately, we postulate that, similar to other disruptive technology in our field (eg, 3D planning, IMRT,
image-guided radiation therapy, etc.), the value of MRgRT will be borne out in due course. MRgRT
represents more than just another more accurate treatment modality but is a potential departure from
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