Step-and-shoot spot-scanning proton arc therapy (SPArc)

A team of U.S. experts at Corewell Health William Beaumont University Hospital has achieved a medical first by successfully treating a patient’s adenoid cystic carcinoma using a novel technique called step-and-shoot spot-scanning proton arc therapy (SPArc). This groundbreaking treatment was published in the June 2025 issue of the International Journal of Particle Therapy.

The SPArc technique marks a significant advancement in radiation therapy, particularly for tumors located in anatomically complex areas, such as the skull base. The team compared SPArc with the current standard of care, SFO-IMPT (spot-scanning proton arc therapy with a fixed-gantry), and found that SPArc methods significantly reduced radiation exposure to critical surrounding tissues.

Key benefits of SPArc observed in the study include:

• Reduced radiation to vital organs: SPArc methods decreased radiation delivered to the brainstem by 10%, the optical chiasm by 56%, the oral cavity by 72%, and the spinal canal by a remarkable 90% compared to SFO-IMPT.
• Precise targeting: SPArc works by precisely targeting tumors with protons, effectively minimizing damage to healthy surrounding tissues.
• Potential for complex and extensive tumors: The technology is expected to be highly valuable for tumors requiring precise dose delivery with minimal spillage to critical adjacent areas, as well as for large or extensive tumors where accurate targeting with limited collateral damage is crucial.

The first patient to receive this innovative step-and-shoot SPArc treatment was a 46-year-old woman with parotid-gland cancer that had aggressively spread along her facial nerve towards the base of her skull. This successful application demonstrates the potential of SPArc to revolutionize treatment for challenging cancer cases.

(Source: TH)