Data from The Advantage of FLASH Radiotherapy Confirmed in Mini-pig and Cat-cancer Patients

Abstract

<div>AbstractPurpose:<p>Previous studies using FLASH radiotherapy (RT) in mice showed a marked increase of the differential effect between normal tissue and tumors. To stimulate clinical transfer, we evaluated whether this effect could also occur in higher mammals.</p>Experimental Design:<p>Pig skin was used to investigate a potential difference in toxicity between irradiation delivered at an ultrahigh dose rate called “FLASH-RT” and irradiation delivered at a conventional dose rate called “Conv-RT.” A clinical, phase I, single-dose escalation trial (25–41 Gy) was performed in 6 cat patients with locally advanced T2/T3N0M0 squamous cell carcinoma of the nasal planum to determine the maximal tolerated dose and progression-free survival (PFS) of single-dose FLASH-RT.</p>Results:<p>Using, respectively, depilation and fibronecrosis as acute and late endpoints, a protective effect of FLASH-RT was observed (≥20% dose-equivalent difference vs. Conv-RT). Three cats experienced no acute toxicity, whereas 3 exhibited moderate/mild transient mucositis, and all cats had depilation. With a median follow-up of 13.5 months, the PFS at 16 months was 84%.</p>Conclusions:<p>Our results confirmed the potential advantage of FLASH-RT and provide a strong rationale for further evaluating FLASH-RT in human patients.</p><p><i>See related commentary by Harrington, p. 3</i></p></div>