Proton Therapy Improves Survival in Patients With Lower Grade Glioma

Investigators at Mass General Brigham reported that proton therapy helped patients with lower grade glioma live longer without their cancer worsening while experiencing fewer long-term side effects, according to results from a prospective phase 2 clinical trial published in Neuro-Oncology. The study evaluated whether this targeted form of radiation could better protect healthy brain tissue and preserve quality of life for patients who often live many years after treatment.

Researchers found that proton therapy provided strong tumor control and limited radiation exposure to normal tissue, which may help maintain cognition, hormone function and daily well-being compared with traditional photon radiation.

Main data that support the findings

The single-arm trial followed 63 adults with lower-grade gliomas treated with proton therapy. After five years, 79.1% of patients remained free from tumor progression. Overall survival reached 85.6%.

Investigators also reported that progression-free survival was significantly better compared with older data using traditional photon therapy.

Beyond tumor control, the study focused on how patients felt and functioned over time. At the start of the trial, 34% of participants had issues with brain function. That proportion increased to 43% after five years. Despite this change, only one patient experienced severe side effects.

According to the study team, these findings suggest proton therapy may reduce the kinds of cognitive and hormonal problems often associated with conventional radiation, particularly for patients expected to live many years after diagnosis.

“Proton therapy limits radiation exposure to surrounding healthy tissues, which helps preserve important functions like neurocognitive and hormonal health,” said Dr. Helen Shih, a radiation oncologist with the institute, in a news release from Mass General Brigham. She added that the treatment showed the potential for improved quality of life in patients.

Lower grade gliomas include World Health Organization grade 1 to 2 and favorable grade 3 tumors. They often affect younger adults and are linked with longer survival. Many patients live five to 10 years or more, and an increasing number live beyond two decades. Because of this longer life expectancy, minimizing treatment-related side effects becomes especially important.

Trial details

The research team conducted the study at Massachusetts General Hospital between 2010 and 2018. Adults age 18 or older with lower grade gliomas and various tumor mutations were eligible to enroll.

The primary endpoint was progression-free survival, defined as how long patients lived without their cancer worsening. Secondary endpoints included cognitive function, hormonal function, quality of life and overall survival. Investigators also tracked treatment-related side effects.

Participants underwent follow-up evaluations at least annually for five years or longer.

Proton therapy differs from conventional X-ray radiation by limiting the amount of radiation delivered to healthy tissues. By focusing the radiation more precisely on the tumor, clinicians aim to lower the risk of long-term complications that can affect memory, thinking, hormone balance and daily functioning.

The authors noted that the study design did not include a comparison group treated with photon therapy, which may limit how broadly the results can be applied. They also stated that randomized controlled trials are ongoing to directly compare proton therapy with traditional radiation. Longer follow-up beyond seven years is planned to better understand durability of benefit and late side effects, especially related to neurocognitive function.

Safety

Safety was closely monitored throughout treatment and follow-up. Researchers tracked side effects, including cognitive and hormonal changes.

Only one patient experienced severe side effects during the study period. The overall rate of serious toxicity was low, which the investigators said supports proton therapy as a safer option compared with traditional radiation approaches.

Because patients with lower grade gliomas often live many years, the ability to reduce long-term toxicities may play an important role in preserving independence, work and everyday activities after treatment.

Reference

1. “Cognitive Function, Quality of Life, and Survival Outcomes in Patients with Lower Grade Gliomas Treated with Proton Radiation Therapy: A Phase II Study” by Dr. Helen Shih, et al., Neuro-Oncology.

Editor's note: This article is for informational purposes only and is not a substitute for professional medical advice, as your own experience will be unique. Use this article to guide discussions with your oncologist. Content was generated with AI and reviewed by a human editor.

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