Dottorato in FISICA DEGLI ACCELERATORI

Titolo della tesi: Performance of very high-energy electron therapy delivered in conventional and FLASH conditions: the case of Stereotactic treatments

Cancer is one of the leading causes of death in the world. Several therapies have been adopted, with photon Radiotherapy (RT) frequently favoured or treated in conjunction with surgery and chemotherapy. RT can intervene in 65% of cancer cases but leaves a sizable number of patients with untreatable tumours, such as radioresistant tumours. Very High-Energy Electron beams (VHEE) delivered at very high dose rates, and thus benefiting from the FLASH effect, may be a viable alternative to conventional treatment plans for the treatment of deep-seated tumours. Experimental data providing evidence of considerable sparing in normal tissue when treatments are delivered at much higher doses rates (100 times or greater) than conventional ones has been growing steadily since 2019. Lung cancer and pancreatic cancer are the two biggest cancer killers, stereotactic treatment is often prescribed precisely to give patients a higher dose and thus root out their tumors. But precisely because of this high prescribed dose, the Organ At Risk (OAR) are often difficult to spare. In the case of stereotactic treatment of pancreatic cancer, Dose Volume Histograms (DVH) show how the delivery of FLASH treatments may allow duodenum sparing compared with conventional photon therapy and finally allow a higher dose to be prescribed at patient’s target while keeping stereo constraints respected. In the case of lung cancer, the advantages of this technique are further enhanced by reducing lung fibrosis produced by radiation on healthy tissues. During the project, I have studied the application of the VHEE technique in a clinical case to evaluate the possibility of applying this method to clinical practice by comparing the results with the state of the art in terms of treatments currently existing in hospitals. The results demonstrate that FLASH effect therapy with VHEE beams of 70-130 MeV, could represent a promising alternative to standard radiotherapy by allowing a significant sparing of the healthy tissues.