Clinical Trial Shows Survival Benefit With Proton Therapy

Results of a Phase III clinical trial published recently in The Lancet show that oropharyngeal cancer patients receiving proton therapy kept their cancer under control just as well as patients receiving traditional radiation therapy, or photon therapy. Importantly, patients treated with proton therapy were more likely to be alive at the five-year mark of the study and suffered fewer side effects than those receiving photon therapy. The trial is considered the largest of its kind to compare the treatments.

“Before the publication of this paper, there weren’t any data showing us that protons were better than photons for treating oropharyngeal cancer, the most common type of head and neck cancer,” said study co-author Christina Henson, M.D., an associate professor of radiation oncology at the University of Oklahoma College of Medicine. “Although the trial was designed to study whether protons were just as good as photons for treating oropharyngeal cancer, one of the major unexpected findings was that the rate of patients being alive at five years after treatment was 10% higher in those who received proton therapy.”

Henson said the researchers hypothesize that proton therapy patients lived longer because they had less treatment-related toxicity. White blood cell counts did not drop as much, and fewer patients needed feeding tubes because of painful irritation of the throat and mouth. Proton therapy patients also had improved weight maintenance and overall better quality of life.

“The rates of cancer coming back were approximately the same in the proton and photon arms of the trial, so the longer survival time wasn’t due to the cancer itself,” Henson said. “There was likely less effect on the immune system with proton therapy, which may have translated to improved survival outcomes. Patients receiving photon therapy received radiation to a larger area of their body, which may have affected more of the bone marrow and lymph nodes, and therefore impacting the immune system more.”

Proton therapy is a type of radiation therapy that goes a certain depth into the body (to the tumor) and stops, whereas photon therapy enters and exits the body, affecting more of the body with radiation, including normal areas.

Although the trial was conducted in patients with oropharyngeal cancer (cancers of the tonsils or the back part of the tongue), Henson said the findings may be applicable to other types of head and neck cancer. Researchers also hope these trial results will prompt insurers to cover proton therapy treatment, which can otherwise be cost-prohibitive.

The trial was led by University of Texas MD Anderson Cancer Center and enrolled 440 patients at 21 institutions, including OU, that treat a large volume of patients with head and neck cancers. Henson said studies consistently show that outcomes are better when patients are treated at high-volume centers with specialty expertise.

“We treat many patients with proton therapy at OU Health Stephenson Cancer Center, and we fully expect the results of this study to make proton therapy an option for many more people.”

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About the project

The study, “Proton versus photon radiotherapy for patients with oropharyngeal cancer in the USA: a multicentre, randomised, open-label, non-inferiority phase 3 trial,” can be found at https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(25)01962-2/fulltext.

About the University of Oklahoma

Founded in 1890, the University of Oklahoma is a public research university with campuses in Norman, Oklahoma City and Tulsa. As the state’s flagship university, OU serves the educational, cultural, economic and health care needs of the state, region and nation. In Oklahoma City, the OU Health Campus is one of the nation’s few academic health centers with seven health profession colleges located on the same campus. The OU Health Campus serves approximately 4,000 students in more than 70 undergraduate and graduate degree programs spanning Oklahoma City and Tulsa and is the leading research institution in Oklahoma. For more information about the OU Health Campus, visit www.ouhsc.edu.