ESTRO 2024 - Abstract Book

S5558

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2024

particularly in the longitudinal position shows the significant target motion and the uncertainty in relying on a surrogate, either bone or diaphragm for accurate treatment to the target.

Longitudinal

Vertical

Lateral Lower LOA

Conclusion:

Upper LOA

Upper LOA

(cm)

Lower LOA

Lower LOA

Upper LOA

This research demonstrates the challenges of using surrogate structures for

Bone vs Target

-1.24

0.85

-0.43

0.66

-0.73

0.62

Target

vs

Diaphragm

-1.63

1.49

-

-

-

-

Bone vs Diaphragm

-1.97

1.43

-

-

-

-

precise treatment delivery in middle and lower third oesophageal cancer. Although the data shows stronger agreement between bone and target matches, which aligns with current and recommended practice (The Royal College of Radiologists, 2021), there was still significant variation in target position and bony match. However, the study's focus on image matches rather than dosimetric implications limits definitive conclusions. The discrepancies with other studies may arise from non-visible soft tissue anatomy exclusion and CBCT image quality limitations. Possible solutions include abdominal compression and advanced techniques such as online adaptive planning or MR Linacs to address diaphragm displacement and enhance treatment accuracy in oesophageal cancer patients. However until these modern radiotherapy treatment techniques are widely available, further development, such as improving CBCT image quality and utilising 4DCT planning data is required.

Keywords: IGRT, Oesophagus, Diaphragm

References:

References

Gao, H., Kelsey, C. R., Boyle, J., Xie, T., Catalano, S., Wang, X., & Yin, F.-F. (2019). Impact of Esophageal Motion on Dosimetry and Toxicity With Thoracic Radiation Therapy. Technology in Cancer Research & Treatment, 18, 1533033819849073. https://doi.org/10.1177/1533033819849073

The Royal College of Radiologists. (2021). On target 2: updated guidance for image- guided radiotherapy.

Visser, S., den Otter, L. A., Ribeiro, C. O., Korevaar, E. W., Both, S., Langendijk, J. A., Muijs, C. T., Sijtsema, N. M., & Knopf, A. (2022). Diaphragm-Based Position Verification to Improve Daily Target Dose Coverage in Proton and Photon Radiation Therapy Treatment of Distal Esophageal Cancer. International Journal of Radiation Oncology*Biology*Physics, 112(2), 463–474. https://doi.org/https://doi.org/10.1016/j.ijrobp.2021.09.015 Voncken, F. E. M., Nakhaee, S., Stam, B., Wiersema, L., Vollenbrock, S. E., van Dieren, J. M., van Leerdam, M. E., Sonke, J.-J., Aleman, B. M. P., & Remeijer, P. (2020). Quantification of Esophageal Tumor Motion and Investigation of Different Image-Guided Correction Strategies. Practical Radiation Oncology, 10(2), 84–92. https://doi.org/10.1016/j.prro.2019.11.012