MSK radiation oncologist Dr. Yao Yu says proton therapy can control brain and spine tumors with less damage to normal tissue. The sophisticated form of radiation has recently proved effective in the treatment of leptomeningeal metastases.
People with tumors of the central nervous system (CNS), which includes the brain and spinal cord, are living longer after treatment. The increase in survival makes it even more important to minimize the treatment side effects that can impair day-to-day life.
One way Memorial Sloan Kettering radiation oncologists are reducing side effects is through the use of a sophisticated form of radiation called proton therapy. Proton therapy kills cancer cells by damaging their DNA, similar to the process used in conventional X-ray radiation. But while traditional radiation uses beams of X-rays, proton therapy targets tumors with charged particles, called protons.
The unique physical properties of protons allow them to deliver the radiation dose at a specific depth in the body. X-rays release their energy both before and after they hit their target. With proton therapy, all energy is released when it reaches the tumor, which can help to reduce the radiation dose to normal tissues.
This month, MSK marks the five-year anniversary of treating patients at the New York Proton Center (NYPC), a state-of-the-art facility in Manhattan opened in collaboration with two other institutions. The NYPC recently treated its 5,000th patient — most of those patients have been referred by MSK and treated by MSK radiation oncologists.
Memorial Sloan Kettering Cancer Center (MSK) radiation oncologist Yao Yu, MD, discusses how MSK is using proton therapy to further advance treatment of CNS tumors.
Precision Spares Delicate Tissues
MSK’s radiation oncologists use proton therapy to treat a range of brain tumors and spine tumors. These include:
- leptomeningeal metastases (cancer that has spread to the space containing the brain, spinal cord, and cerebrospinal fluid)
- gliomas
- meningiomas (slow-growing, noncancerous tumors that form in the membranes that surround the brain)
- pituitary tumors
- brain metastases (cancer that has spread to the brain from another part of the body)
- schwannomas (tumors of the tissue covering nerves)
Often, these patients have previously been treated with X-ray radiation, but the disease has grown resistant or progressed.
“The precision of proton therapy can be critical for protecting the brain’s delicate tissues,” Dr. Yu says. “While protons aren’t necessary for all brain tumors, they can offer an advantage over other types of radiation. Proton therapy can limit the amount of normal brain tissue receiving radiation, which reduces the effects on important functions, such as cognition, vision, and hearing.”
Scaling Up to Help More Patients
MSK radiation oncologists carefully consider whether proton therapy may be appropriate for each patient. MSK is looking to increase the number of patients who may benefit from this advanced form of radiation. For example, CNS radiation oncology specialists increasingly consider using proton therapy on some brain tumors that have come back.
“Treating these cancers can be challenging depending on the location of the tumor,” Dr. Yu explains. “Often, people with these recurrent tumors have received significant radiation doses in the past to important parts of the brain. These may include optic nerves, which are critical to vision, and the brainstem, which regulates many essential body functions, such as breathing, heart rate, and swallowing.”
The CNS team is also exploring proton therapy for some people with noncancerous tumors of the central nervous system. People with these tumors survive for a long time, so it is even more important to limit radiation doses to normal tissue to reduce the potential for radiation-induced side effects.
Proton Therapy for Leptomeningeal Metastasis: Clinical Trial Results
MSK experts are designing clinical trials that test new approaches for other CNS cancers. In particular, investigators at MSK have shown the effectiveness of proton therapy in the treatment of leptomeningeal disease.
A phase 2 clinical trial showed that in patients with leptomeningeal metastases who received proton therapy to the brain and spine (also called proton craniospinal irradiation), the disease remained stable more than three times longer compared with those who got conventional radiation. Those who received proton therapy also lived more than one-and-a-half-times longer than those getting standard radiation.
“The trial showed that proton craniospinal irradiation resulted in improved control of the cancer in the brain and spine, and better overall survival compared with standard approaches,” Dr. Yu says. “It also showed that proton therapy significantly reduced side effects of craniospinal irradiation compared with standard approaches.”
More clinical trials testing proton therapy for CNS cancers — either alone or combined with other treatments — will begin at MSK as evidence of its effectiveness mounts.
