Evaluating VHEE radiotherapy treatment plans for prostate and lung cancer

Master thesis (2023)

Authors

B. Spek Applied Sciences

Contributors

D. Lathouwers RST/Reactor Physics and Nuclear Materials - AS (supervisor 1)
Sebastiaan Breedveld Erasmus MC (supervisor 2)
Faculty
Applied Sciences
Copyright: © 2023 Bob Spek
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Published Date

21-06-2023

Language

English

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Faculty

Applied Sciences

Abstract

Over 50% of cancer patients will receive radiotherapy treatment at least once. Most patients are receiving photon radiotherapy. In this work very high energy electron (VHEE) radiotherapy is being studied as a potential replacement for photon radiotherapy. VHEE beams have a favorable depth dependence and the penumbra of VHEE pencil beams stays small deep inside the patient. Therefore, using VHEE radiotherapy can potentially result in a lower dose being delivered to the organs at risk (OAR) in comparison with clinically used volumetric modulated arc therapy (VMAT). New accelerator techniques allow VHEE beam generators to fit in standard radiotherapy treatment bunkers. Therefore, VHEE therapy can reduce the equipment costs in comparison with proton therapy and it can increase the treatment quality in comparison with photon therapy. In this work the VHEE treatment plans are compared with clinically used VMAT treatment plans for prostate and lung cancer.

VHEE treatment plans were generated for 6 patients with prostate cancer and 3 patients with lung cancer. First, the pencil beam dose distributions were calculated for each patients using a Monte Carlo particle simulation tool called TOPAS MC. Thereafter, the optimal intensities of the pencil beams were calculated using iCycle, an automated optimization tool, which calculates the optimal treatment plan. The VHEE treatment plans are generated with 9, 18 and 36 beams and the energies that are used are: 100, 200, 300 and 400 MeV. The treatment plans were normalized to a 99% PTV coverage of 95% of the prescribed dose.

For the prostate case, the 100 MeV VHEE treatment plans deliver more dose to the organs at risk (OARs) than the VMAT plan. The 18 beam 300 and 400 MeV VHEE treatment plans showed a dose reduction in the mean dose of the patient, the rectum, the anus and the bladder, but a dose increase to the left and right femoral heads. The 18 beam 400 MeV treatment plan reduced the dose to all OARs in comparison with the VMAT plan, for the lung cases. Increasing the number of beams of the VHEE treatment plan reduces the dose to the OARs, for both the prostate and the lung cases. Increasing the energy of the electron beams also reduces the OAR dose for both cases.

VHEE plans reduce the dose to the healthy tissue, while keeping the PTV dose constant and can therefore be considered as a possible replacement for photon radiotherapy.