- What is proton beam therapy and for what is it used?
- Why is proton beam therapy used?
- How is proton beam therapy done?
- How effective is this therapy in treating liver cancer?
- What are the potential risks and benefits of proton beam therapy?
- What are the potential side effects of proton beam therapy?
- What research is being done on proton beam therapy?
How is proton beam therapy done?
Proton beam therapy is typically done in an outpatient setting. Prior to the start of proton beam therapy, the patient undergoes a CT or MRI scan to localize the exact site of the cancer. The scan is performed with the patient sitting or lying in a device that immobilizes the part of the body that will undergo therapy. Based on the scan, plans are made to deliver the proton beam to the cancer. For each session of therapy, the patient is placed again in the immobilization device. In addition, X-rays or scans are taken before every session to make sure the patient is in the exact same position so the protons hit the tumor and not the surrounding healthy tissue.
The proton beam is invisible and painless. The number of treatment sessions depends on the type and stage of the cancer being treated. Therapy usually is conducted 5 days per week, usually for 15 days. Proton beam therapy sessions last about 15 to 30 minutes.
How effective is this therapy in treating liver cancer?
Proton beam therapy is a relatively new treatment modality. There is not yet much data regarding the efficacy of this treatment for liver cancer. Preliminary data from the U.S. suggest similar effectiveness as seen with transarterial chemoembolization (TACE) or ablation (using radiofrequency or alcohol) for the treatment of HCC. It is not known whether this type of radiation treatment can consistently prolong the life of the patient.
A study from Loma Linda University Medical Center showed proton beam therapy was effective in treating cancerous lesions in the liver up to 10 centimeters. Patients with one lesion smaller than 5 centimeters or up to three lesions smaller than 3 centimeters (this size definition is called the Milan criteria) have better survival rates than patients with larger tumors. The same study found that patients who had tumors within the Milan criteria that were treated with proton beam therapy had a 48% survival rate over 3 years. Those whose tumors fell outside the definition of the Milan criteria had 3-year survival rates of 12%.
Another study at the University of Tsukuba in Japan looked at the safety and efficacy of using proton beam therapy to treat metastatic liver cancer (cancer that had spread to the liver from elsewhere in the body), and it found the treatment to be both safe and effective. Those who had cancer only in the liver had better outcomes than those whose cancer had spread more widely.