The technique, known as step-and-shoot proton arc therapy, has been successfully used in a recent case involving a rare and invasive salivary gland cancer, with results that specialists say could mark a significant advance in cancer care. Unlike conventional radiation methods, the approach precisely targets tumours while sparing surrounding healthy tissue, leading to minimal toxicity.
The method was pioneered by physicians and scientists at Corewell Health William Beaumont University Hospital in Royal Oak, Michigan. Early outcomes suggest that patients can undergo intensive radiation treatment with little to no long-term side effects. In one reported case, the only side effect observed was mild skin discolouration, even nine months after treatment.
Radiation oncologists note that traditional cancer radiation often causes fatigue, pain, swallowing difficulties, nerve damage and cognitive issues, particularly when tumours are located near critical organs. The step-and-shoot proton arc system aims to reduce these risks by using an automated proton beam that delivers radiation continuously and with extreme precision.
Unlike older proton therapies that require manual repositioning between doses, the new system adjusts beam angles automatically, eliminating delays and reducing the risk of inaccuracies. This allows radiation to conform more closely to the tumour’s shape while limiting exposure to nearby organs.
The benefits of the treatment were evident in the case of 46-year-old Tiffiney Beard from Redford, Michigan, who was diagnosed in early 2024 with adenoid cystic carcinoma—a rare, nerve-seeking cancer of the salivary gland that is notoriously difficult to treat.
According to Dr Rohan Deraniyagala, a radiation oncologist at Corewell Health, such tumours often spread along nerve pathways, making treatment particularly challenging and increasing the likelihood of serious side effects.
“These cancers tend to invade nerves, so treatment can result in fatigue, jaw pain, difficulty eating or swallowing, loss of taste, headaches and memory problems,” Deraniyagala explained.
Beard became the first patient in the United States to receive the advanced proton beam arc therapy for a head-and-neck cancer. After surgical removal of the tumour—roughly the size of a gumball—she underwent 33 proton therapy sessions.
Remarkably, she experienced virtually no side effects and did not miss a single day of work during treatment.
“You hear so many stories about radiation being debilitating,” Beard said. “But I had no side effects at all. I just wasn’t experiencing what people usually talk about.”
In her case, the tumour had extended into nerves leading toward the brain, an area where conventional radiation could pose significant risks. Nearly a year after completing treatment, Beard remains cancer-free, with no evidence of radiation damage to surrounding organs, including the brain.
Deraniyagala confirmed that follow-up evaluations show no radiation toxicity and described the outcome as highly encouraging, while cautioning that individual responses to treatment can still vary.
Building on this success, researchers at Corewell Health’s William Beaumont University Proton Therapy Centre are now testing a next-generation system known as DynamicARC. The technology is designed to further refine proton beam delivery by eliminating any lag time between radiation doses and beam angles.
Through collaboration with Ion Beam Applications, an international proton therapy manufacturer, scientists hope to enhance the step-and-shoot approach and make treatments even faster, more precise and safer.
Experts say while broader clinical trials are still needed, the early results suggest that advanced proton arc therapies could significantly change how complex cancers are treated—offering patients effective tumour control without the heavy burden of long-term side effects.