ESTRO 2024 - Abstract Book

S3493

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2024

The MCO can provide treatment plans with significant OARs’ sparing improvement with no significant worsening of target dose homogeneity. Therefore, it can be used as an appropriate tool for patients undergoing radiotherapy for the treatment of glioma cancer.

Keywords: VMAT, Multi-criteria optimization, Glioma Cancer

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Electron RT for perianal squamous cell carcinoma: dose, fractionation, technique, and local control

Bjarke Mortensen 1,2 , Birgitte Mayland Havelund 1 , Sean Patrick McIlroy 1,2 , John Pløen 1 , Lars Ulrik Fokdal 1,3

1 Department of Oncology, Vejle Hospital, University Hospital of Southern Denmark, Vejle, Denmark. 2 Radiotherapy Research Team, Department of Oncology, Vejle Hospital, University Hospital of Southern Denmark, Vejle, Denmark. 3 Department of Regional Health Research, University of Southern Denmark, Odense, Denmark

Purpose/Objective:

Perianal squamous cell carcinoma (SCC) is an uncommon lesion that comprises 3-4% of all anal malignancies. Treatment options include a wide local excision or radiotherapy (RT) and the treatment choice should be balanced between the chance of achieving a tumor-free resection margin and anal sphincter preservation. At Vejle Hospital, University Hospital of Southern Denmark selected patients with early state perianal SCC are treated with electron beam RT. This study presents the technique and evaluates the adequacy of the treated volume by assessing possible geographical miss and local control (LC).

Material/Methods:

All patients with early-stage perianal SCC treated with electron beam RT from 2012 to 2022 at our hospital were included in this study. Patients were positioned on a gynaecological couch and treated with a single “eye-guided” perianal electron field. Standard circular electron apertures and electron energy were chosen by the radiation oncologist based on clinical assessment of the tumour extent at the anus and along the anal canal. By the prescription, a cylindrical planning target volume is thus defined by 85% of the prescription dose, given the aperture including a margin of at least 15 mm (5 mm margin from GTV to PTV plus 10 mm margin from PTV to the edge of the circular aperture) and the therapeutic range given by the electron energy. This cylindrical volume must encompass the tumour. A simple factor-based monitor unit calculation was performed by the medical physicist. Clinical information regarding diagnosis, prescription, dosimetric treatment parameters, and outcome was retrospectively extracted from clinical records. Prescription, dosimetric treatment parameters, and LC were analysed regarding potential geographical miss.

Results: