Meningioma is the most common benign tumor of the central nervous system in adults, accounting for approximately 36% of all brain tumors.

The World Health Organization (WHO) classifies meningiomas as pathological grade I-III, with most meningiomas classified as WHO grade I, with slow growth and good prognosis;

Approximately 10% -25% of meningiomas are classified as WHO grade II - III, presenting with atypical clinical features and frequent recurrence, but with minimal extracranial metastasis.

Surgical treatment is the main treatment method for meningiomas, and radiation therapy can be used as an auxiliary treatment for partial resection, high-grade lesions, or recurrent lesions.

For areas that cannot be removed, radiation therapy can also be used as a radical treatment method.

In recent years, radiation therapy technology has developed rapidly, but traditional radiotherapy still causes normal tissues around tumors to receive large volumes of low-dose radiation.

This increases the probability of adverse reactions occurring in normal brain tissue around the tumor.

The main adverse reactions of brain tissue after radiation therapy include visual impairment, pituitary dysfunction, hypothalamic dysfunction, epilepsy, brain tissue necrosis, paralysis, long-term cognitive impairment, and secondary primary tumors.

The International NeuroSurgeons Group (INC) is a physician group that focuses on academic exchanges among internationally renowned experts in the field of neurosurgery worldwide.

According to the INC official website, proton therapy is usually recommended for brain tumors due to their proximity to fragile and crucial normal tissues and structures.

Proton therapy can further increase the treatment ratio of radiation therapy to primary brain tumors.

Due to the deposition of most of the energy of proton rays at the end of the range, a steep dose peak (Bragg peak) is formed at the end, and the dose after the peak suddenly drops to zero. Before the peak, there is a low-dose plateau, and the dose is much lower than the peak.

Therefore, proton therapy can avoid or reduce the radiation dose of normal tissues around tumors, thereby avoiding or reducing the occurrence of early and late adverse reactions in normal tissues.

Therefore, for tumors with a large number of important surrounding tissues and organs such as brain tumors, proton therapy can effectively avoid or reduce adverse reactions in the later stage, greatly improving the quality of life of patients after treatment.

Proton therapy for meningioma can reduce the radiation dose to key brain structures near the tumor and reduce the overall dose to the brain.

A radiation dose study compared photon radiotherapy and proton therapy techniques for 20 meningiomas with tumors larger than 3 centimeters.

Research has shown that the average dose and brain volume received at moderate radiation doses (i.e. 20-30 Gy) decreased by 50% under proton therapy [4].

Proton therapy can reduce the radiation dose and volume of normal tissues around tumors by half.

In addition, the dose comparison analysis of other proton therapy and photon radiation therapy also shows that the total radiation dose to the brain of the photon radiation therapy scheme is significantly higher, while the use of proton therapy can reduce the total dose by about 50%.

The Orsay Proton Therapy Center in France treated 17 meningioma patients with photon combined with proton therapy, with a median GTV (tumor area) total dose of 61 CGE.

The 4-year local control rate and survival rate were 87.5% and 88.9%, respectively, with most patients experiencing complete remission (CR) or some patients experiencing (PR) [3].

Massachusetts General Hospital in the United States treated 46 patients with benign meningioma using photon combined with proton therapy, with a median tumor area dose of 59 CGE.

The overall survival rates at 5 and 10 years were 93% and 77%, respectively; The 5-year and 10-year recurrence free survival rates were 100% and 88%, respectively.

Massachusetts General Hospital also compared the results of the photon group and the combined proton group in the treatment of malignant meningiomas, and found that the overall control rate and long-term survival rate of the combined proton group were significantly higher than those of the single photon group.

A study released by the Paul Scherrer Institute in Switzerland in 2020 systematically evaluated the results of proton therapy for meningioma.

The study showed that the overall 5-year survival rate of proton therapy for WHO grade I meningiomas was 96.2%, and the 5-year progression free survival rate was 96.6%.

The 5-year local control rate for WHO grade II - III meningioma patients receiving proton therapy with over 60 GyRBE was 87.5%, while the 5-year local control rate for those receiving proton therapy with less than 60 GyRBE was 50%.

The 1-year and 2-year overall survival rates of proton therapy and re irradiation for recurrent meningiomas after radiotherapy were 89.6% and 71.4%, respectively.

Overall, proton therapy for meningioma not only has excellent results, but also can greatly reduce the radiation dose to normal tissues around the tumor, thereby reducing radiation toxicity and reducing the risk of adverse reactions in the later stage.