ESTRO 2024 - Abstract Book

S4123

Physics - Inter-fraction motion management and offline adaptive radiotherapy

ESTRO 2024

References:

[1] Nordsmark M, Overgaard J. A confirmatory prognostic study on oxygenation status and loco-regional control in advanced head and neck squamous cell carcinoma treated by radiation therapy. Radiother Oncol 2000;57:39–43.

[2] Olteanu L, Duprez F, De Neve W, Berwouts D, Vercauteren T, Bauters W, Deron P, Huvenne W, Bonte K, Goethals I, Schatteman J & De Gersem W. Late mucosal ulcers in dose-escalated adaptive dose-painting treatments for head and-neck cancer, Acta Oncologica, 2018;57:2, 262-268, DOI: 10.1080/0284186X.2017.1364867 [3] Zschaeck S, Löck S, Hofheinz F, Zips D, Saksø Mortensen L, Zöphel K, et al. Individual patient data meta-analysis of FMISO and FAZA hypoxia PET scans from head and neck cancer patients undergoing definitive radio-chemotherapy. Radiother Oncol 2020;149:189–96. https://doi.org/10.1016/J.RADONC.2020.05.022.

3164

Digital Poster

Treatment planning on a diagnostic CT scan is infeasible without plan adaptation in rectal cancer

Claudia S.E.W. Schuurhuizen, Maaike T.W. Milder, Judith H. Sluijter, Maarten L.P. Dirkx, Joost J.M.E. Nuyttens

Erasmus MC, Radiation Oncology, Rotterdam, Netherlands

Purpose/Objective:

Currently, part of the standard workflow to prepare (chemo)radiotherapy treatment for rectal cancer is the acquisition of a planning CT scan, followed by delineation of the target volumes and organs at risk, and generation of a radiotherapy treatment plan. During this workflow, until start of treatment, patients often suffer from rectal pain, fecal occult blood in stool, anemia and diarrhea. A faster start of (chemo)radiotherapy treatment could prevent, delay progression, or even improve some of these complaints. A new development in the radiotherapy field is adaptive radiotherapy. This technique can be used to reduce the time to start of treatment, by using the already available, most recent diagnostic CT scan for treatment preparation. The aim of this retrospective study is to investigate in silico the feasibility of delineation and treatment planning on a diagnostic CT scan. Primary endpoint is to validate whether this plan may be used for treatment without plan adaptation.

Material/Methods:

This retrospective study was approved by the ethical committee of our institute (MEC-2023-0092). For this study, we used data of 15 patients with stage II or III rectal cancer. Delineation was done on both the diagnostic CT scan and planning CT scan. The CTV was delineated according to standard guidelines, the PTV margin consisted of 10 mm in all directions. OARs included the bladder, femur heads and a derived bowelbag structure. The diagnostic CT scan was used for planning of an intensity-modulated radiotherapy (IMRT) treatment plan (8 patients), or a volumetric