Proton Therapy for Brain Tumors

What Is Proton Therapy?

Proton therapy (Proton Beam Therapy, PBT), conventional radiation therapy uses high-energy proton particles instead of the X-rays used in that approach and is a radiotherapy method. A cyclotron accelerates and energizes protons, which are then directed to the planned tumor site. They release tumor-destroying energy at a specified tissue depth, determined before treatment from patient condition and tumor location and size, and adjustable.

How Does It Differ from Conventional Radiotherapy?

Conventional X-rays release some energy before reaching the tumor and continue releasing it until exiting the opposite side of tissue, such as the brain. Normal cells along the path are therefore injured.

In proton therapy, this problem is partially improved. Proton particles target cancer cells more specifically, preventing potential normal-cell injury.

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Highly targeted delivery benefits tumors near sensitive areas such as the spinal cord or optic nerves. This matters especially in children whose brains are developing; thus, proton therapy has become standard most commonly for pediatric brain tumors , for example medulloblastomas. For adult spinal tumors and situations where reducing adverse effects is critical, proton therapy and intensity-modulated radiotherapy (Intensity-Modulated RadioTherapy, IMRT) are two important options.

Before deciding to use proton therapy, oncological imaging must carefully establish tumor location and size. It is not suitable for all brain tumors, but mainly small cancers near vital regions.

Which Brain Tumors Preferentially Receive Proton Therapy?

Adults:

• Acoustic neuroma, a benign, usually slow-growing tumor of the sheath of the hearing and balance nerve, cranial nerve 8
• Meningiomas, the most common brain tumors, generally benign
• Pituitary adenomas, usually benign tumors originating in the pituitary gland
• Low- and high-grade gliomas, originating in supporting glial cells
• Chordoma, a rare malignant tumor

Children:

• Juvenile pilocytic astrocytoma, often in the hypothalamus and commonly encountered in children
• Ependymoma, a rare tumor
• Medulloblastoma, the most common childhood brain tumor, often in the cerebellum
• Craniopharyngioma, a benign brain tumor arising from the pituitary gland

What Are Possible Adverse Effects?

Less damage to healthy brain cells than conventional radiotherapy reduces potential adverse effects. However, proton therapy is not free of adverse effects! It may cause fatigue, local redness, and hair loss, some temporary. Long-term pediatric effects may include severe hair loss, impaired thinking and understanding, and adverse effects on hormones such as growth hormone. These also occur after conventional radiation.

Is Proton Therapy Available in Our Country?

No center has yet opened in our country, chiefly because costs greatly exceed standard radiotherapy. It is even 5 times more expensive than advanced intensity-modulated radiotherapy. However, the Turkish Ministry of Health has included it in projects. Developed countries such as Japan, the USA, and the UK offer options, especially for pediatric brain tumors.

A Global View

The USA has the most centers: in 2013 there were 11, rising in 2017 to 28, with 23 more under construction or development.

However, proton centers may face growing pains, according to Lancet Oncology, which published an article on 12 July 2018. Authors reported demand well below expectations in some centers, with financial losses or missed targets. Scripps Proton Therapy Center in San Diego, California, for example, declared bankruptcy.

Virginia's Hampton University Proton Therapy Institute reportedly lost money for the last 5 years, including 3 million dollars in its latest fiscal year.

Nevertheless, the number of centers worldwide is growing.

Despite US market struggles, centers are increasing globally.

The nonprofit Particle Therapy Co-operative Group reports 63 active facilities worldwide, with 32 under construction and 16 planned. Argentina and Australia will soon join, ultimately leaving centers on every continent except Antarctica.

An estimated 165 thousand patients with various cancers have received proton therapy worldwide. Research & Markets forecasts a multibillion-dollar industry by 2024.

In Europe, use increased between 2010 and 2017 by more than 3 times. It primarily treats brain, spinal cord, prostate and stomach solid cancers. Germany, Italy, Sweden, France, Denmark, the Netherlands, Switzerland, Russia, Spain, the UK, Norway, and Belgium are building or planning centers. Research and Markets predicts continued European market growth through 2024.

Approximately % 60 of people live in Asia, accounting for roughly half of global cancer burden. Center numbers in its market are expected to reach double digits from 2018 to 2024. Japan currently leads, while China, Singapore, Thailand, and South Korea are building or planning facilities.

In the Middle East / North Africa, Saudi Arabia opened a center, the UAE is building one, Egypt plans one at Cairo's Children's Cancer Hospital Foundation, and Israel announced finalizing plans. Israel estimates pediatric patients at 150 within approximately 250 patients annually. Construction would cost around 60 million dollars, with another 6 million to operate.

Some countries plan centers because they must send even small numbers abroad, including Australia. Whether national health systems will pay for the expensive treatment at new centers remains unclear.

Despite financial difficulties, the USA is expected to seek continued dominance. Its northern neighbor Canada, however, shows little interestin expanding capacity. It has one facility in Vancouver, British Columbia, a notable research center and internationally leading subatomic physics facility. Patients receive therapy, but only 10 annually.

Operating since 1995, it treats only tumors behind the eye, choroidal melanoma , a malignant melanoma subtype. Canada diagnoses nearly 40 cases annually; about 30 receive brachytherapy, internal radiation, while large tumors or critical optic nerve pressure prompt proton referral.

A Market Still Attracting Interest.

Compared with conventional radiotherapy, superiority in tumor-shrinking effectiveness remains unclear , yet centers grow worldwide. Proton therapy nevertheless represents only %1 of external radiotherapy systems.

In 2017, approximately % 0.1 of cancer patients received it. By 2022, worldwide per 10 million people only 0,5 proton treatment rooms and per 10 million approximately 20 conventional systems are expected.

By 2030, even if the projected 900 to 1300 rooms are built, only %6 to %7 of cancer patients could access proton therapy.

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