Human trial begins for precision FLASH proton therapy

At Penn Medicine’s Roberts Proton Therapy Center in Philadelphia, a sign indicates that the proton beam is active. The room is now hosting a phase 1 clinical trial of ConformalFLASH proton therapy, a precise form of ultra-fast radiation being tested in human patients for the first time in the United States. The study will enroll 10 patients with recurrent head and neck cancer who have already received radiation and cannot undergo surgery.

The practical difference is counted in visits. A typical regimen for these patients involves daily radiation for five to six weeks, usually divided into 25–35 fractions, or separate treatment doses. The FLASH protocol will use five treatments over about 10 days, with each exposure lasting less than a second; patients will complete all five sessions in less than two weeks. The total effective dose remains the same, but it is delivered in fewer, larger doses at very high speed.

That compression matters for patients with recurrent head and neck cancer, whose radiation treatment can affect areas that control eating, drinking and swallowing. Repeat radiation can bring potentially life-altering side effects as well as long hours in medical facilities, according to principal investigator Alexander Lin. His team selected this group because the treatment could offer quality-of-life benefits, while recognizing that the technology is still being tested.

The underlying tools are established separately. Proton therapy uses high-energy protons—positively charged atoms—to damage the DNA of cancer cells. Conformal treatment uses CT or MRI imaging to build a 3D map of the tumor and aim the beam at its boundaries, limiting exposure to nearby healthy tissue as much as possible. FLASH adds speed, using a larger dose delivered in less than a second. Penn’s human study follows a completed FLASH proton trial in pet dogs that used the same head and neck technology. The FDA authorized the platform for this study through an Investigational Device Exemption to IBA, the manufacturer and sponsor.

Concretely, the change for this narrow patient group would be a shorter course: five visits over about 10 days instead of daily treatment for five to six weeks. That could mean less time in medical facilities and, potentially, fewer damaging side effects. The trial is designed to evaluate feasibility and the technology’s benefits and limitations, so those possible gains remain to be established in human patients.