ESTRO 2024 - Abstract Book

S1454

Clinical - Head & neck

ESTRO 2024

3253

Digital Poster

Adaptive radiotherapy, analysis of the indications for replanning in head and neck cancer.

Wojciech Rolski, Aldona Karczewska-Dzionk, Bartosz Weinert

Oncology Centre in Siedlce, Department of Radiation Oncology, Siedlce, Poland

Purpose/Objective:

The study aimed to assess the usefulness of anatomy-adapted radiotherapy protocols and analyse the reasons for replanning radiotherapy in a rural, small-town regional radiotherapy centre.

Material/Methods:

Anatomical changes may have an impact on the dose received, which may be significantly different from the original treatment plan. Changes in the volume of the target and the organs at risk (OARs), as well as in their location, could not only affect the outcome of the treatment but could also increase the severity of the side effects. One solution to this problem is anatomy-adapted radiotherapy (AAR) - the process of analysing the accuracy of the implementation of the assumed treatment plan at predefined intervals, with replanning if indicated during treatment. The protocol adopted at our site includes daily evaluation (starting from the first day of treatment) of cone beam computed tomography (CBCT) images by the experienced radiotherapist and by a team of radiation oncologists and physicists every five days of the treatment course (from the second week of treatment). During weekly assessments, we analysed the degree of tumour regression/progression, size, shape and location of target volumes and OARs. A decision to re-plan radiotherapy was made in the case of setup errors, significant body contour or spatial changes in the target volumes or OARs that could affect the final effect of therapy observed both during daily assessments and weekly expert meetings.

Results:

We analysed data from 151 patients with HNC who were treated between 01/2022 and 06/2023. A total of 32 replans were made (21%). The number of immobilizations performed again was 28 (18,%). The leading reasons for re-planning were: tissue edema, lack of reproducibility, and weight loss in 7, 13 and 15 patients respectively. The indications for replanning were the most common in the 4th and 5th week of treatment (9 and 9 patients respectively).

Conclusion:

The implementation of daily image-guided radiotherapy protocol has shown the possibility of detecting structural and spatial changes during radiotherapy, which may result from a combination of tumour response, weight loss, inflammation and acute radiation reaction of normal tissues.