proton radiation therapy [charged-particle radiation therapy]

Definition of charged-particle radiation therapy
National Cancer Institute

charged-particle radiation therapy

(… PAR-tih-kul RAY-dee-AY-shun THAYR-uh-pee)
A type of external radiation therapy that uses a special machine to make invisible, high-energy particles (protons or helium ions) that kill cancer cells. This type of radiation may cause less damage to nearby healthy tissue than radiation therapy with high-energy x-rays.

Source: NCI Dictionary of Cancer Terms