First-in-human e-Flash radiotherapy using a modified conventional C-arm linear accelerator.

BACKGROUND

The FLASH effect is considered being the widening of the therapeutic window at (ultra-)high dose rates due to sparing of normal tissues while preserving tumor response. Our goal was to provide first data on the safety in treating a patient using a conventional linear accelerator converted to deliver 9 MeV UHDR electron beams in the research setting.

MATERIAL &

METHODS

A conventional Varian TrueBeam linac was converted in the research setting to become capable of delivering 9 MeV UHDR electron beams. A phase I trial protocol was approved by the local authorities (NCT06549439). One patient with ≥ 1 melanoma (sub)-cutaneous lesion(s) was treated with 3x 9 Gy. The first two fractions were applied via e-Flash and the third via conventional electrons.

RESULTS

Here we present the experience of the first patient treated with e-Flash in a modified conventional linac. The e-Flash fractions were successfully delivered according to the protocol. The film in-vivo dosimetry confirmed correctness of the delivered dose. A good tumor response without severe or unexpected toxicity was observed up to six weeks after treatment.

CONCLUSION

We demonstrate first-in-human application of e-Flash delivered by a modified conventional linear accelerator. Conversion of conventional linacs into e-Flash systems will accelerate testing Flash radiotherapy in clinical trials.