ESTRO 2024 - Abstract Book

S108 ESTRO 2024 Standardising complex treatments like Total Body Irradiation (TBI) and Total Marrow and Lymph node Irradiation (TMLI) Invited Speaker

Phil W. Koken 1 , Lars H.P. Murrer 2

1 Amsterdam UMC, Radiation Oncology, Amsterdam, Netherlands. 2 MAASTRO, Radiation Oncology, Maastricht, Netherlands

Abstract:

Introduction Total Body Irradiation (TBI) was first reported in 1905, 10 years after the discovery of X-rays and radioactivity [1]. Over the following decades it was used for a variety of cancers, with the best results being obtained for hematological malignancies. A variety of treatment approaches were developed. With the recent introduction of Tomotherapy and VMAT even more advanced TBI and Total Marrow/Lymph Node Irradiation (TMLI) techniques have become available [2,3]. In order to compare clinical results, differences in techniques and dose-fractionation schemes have become even more important to be taken into account. Results To gain more insight into the variation, a survey was held in 1987 in 15 European countries [4]. The results showed that TBI treatments, techniques, dosimetry and planning varied widely. Subsequent surveys have shown that this variation remains [5-9]. State-of-the-art techniques such as VMAT/TMLI are based on CT-planning, and some centres have incorporated auto-delineation and auto-planning [2-3]. They offer improved sparing of normal tissues, but the complexity of delivery has increased significantly. Automation can reduce preparation and treatment times. Compared to more traditional techniques rotational/arc-based TBI/TMLI usually is still rather time-consuming to prepare and even more complex to perform safely in the clinic. The advantages of these techniques come with challenges for robustness and safety. For example, a combination of head-first and feet first irradiation is necessary to treat an adult patient on a c-arm based linac. The large number of beams and isocentres in combination with the patient rotation halfway through the treatment demands a safe workflow; a prospective risk analysis is needed prior to the introduction of such a technique. Automation of the process might be able to help both safety and performance. In general, it would be helpful if advanced TBI/TMLI converges to a more general technique including (A) auto delineation and auto-planning [2] to shorten preparation times, (B) an easy patient-rotation method to shorten treatment times, to improve patient setup and to prevent errors in performance, which (C) make it easier for others to adopt these treatments. Standardized reporting metrics, including DVH values, should be developed to facilitate inter-institutions comparisons. Attention should also be paid to the dosimetric robustness of TBI/TMLI. For example, older TBI techniques are inherently robust for patient movement due to the large fields used, but the use of multi-field junctions could lead to over/underdosage due to patient movement between beam delivery. In our view, advanced TBI/TMLI technique will become clinically feasible in a safe way only if the structure delineation and treatment planning are automated, and if patient rotation can be performed efficiently and safely. Uniform dose metrics are needed for inter-institutional studies [10]. Discussion/conclusions

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