Frequently Asked Questions
• Does insurance cover proton therapy?Proton therapy is typically covered by Medicare. Most other insurers will cover proton radiation therapy on a case-by-case basis. Our financial coordinators can assist you in working with your insurance company to obtain authorization. For additional information, read Proton Treatment Center as Patient Advocate when Insurance Companies Deny Coverage.
• How is proton radiation therapy planned and delivered?The precision of the proton beam requires equal precision in planning and delivery. This is done in two steps:
1. a three-dimensional reconstruction of the tumor and its relationship to surrounding structures
2. a reproducible treatment position that minimizes movement errors
The three-dimensional information is usually obtained by performing computed tomography (CT) scans through the region of interest (chest, pelvis, etc.) with images taken at 2 to 3 millimeter intervals.
Before performing the CT scan, an immobilization device is made for the patient to reproduce the patient's treatment position each day. Typical immobilization devices include full-body moulds (form-fitting foam liners surrounded by rigid plastic shells) for patients with tumors below the neck. Custom fit masks are made for patients with eye, brain and head tumors or abnormalities. The CT scan is obtained with the patient immobilized in the device and in the treatment position, so that the thickness of the immobilizing material can be taken into account for treatment planning.
Once the immobilization device has been made and the CT scan has been performed, the treating physician traces the tumor and surrounding normal tissues on a computer. This tracing is done image by image to get the most precise map.
Next, physicists and dosimetrists create a treatment plan by outlining on the computer a series of proton beams entering at various angles. From these, they calculate the radiation dose being given to the tumor and normal tissues.
This plan is reviewed by the physician, and once approved, it is transferred electronically to a series of automated machines that make the special devices (apertures and tissue-compensating filters) required by the plan. Before the patient’s first treatment, all of these devices are calibrated by the physics support staff to ensure that the planning and manufacturing are correct.
• How long does the proton radiation stay in my body?Your body does not become radioactive and poses no risk of radiation exposure to others.
• Is proton radiation therapy ever combined?Yes. Conformal proton therapy is often used in conjunction with X-ray therapy. This method boosts the dose to sites of gross disease and allows irradiation of a large tissue volume. Depending on the amount of cancer within a particular lymph node and type of cancer that is present, a patient may be at risk for harboring microscopic nests of cancer cells within the nodes. These nodes may lie at some distance from the primary tumor and may not be irradiated if conformal proton treatment alone is delivered to the tumor.
The objective of the treatment plan is to treat both the primary tumor and any areas where a microscopic tumor might hide. X-ray treatment alone will limit the total dose of radiation that can be given due to the high doses it delivers to large amounts of healthy tissue. Therefore, conformal proton radiation therapy is used to treat the primary tumor, and is then followed by X-ray therapy to treat the regional nodes. By giving some of the treatment with conformal protons, the total X-ray dose can be reduced substantially.
This reduces the risk of complications and permits treatment of potentially involved lymph nodes. Microscopic cancer within these nodes might be missed if X-rays were not used.
• What does "conformal" mean?A "conformal" beam can be shaped, or "conformed,” in three dimensions. The physician can shape the beam to match the shape of a tumor. This helps deliver most of the radiation to the targeted volume while avoiding the surrounding healthy tissue. This unique capability sets proton radiation therapy apart from other forms of external-beam radiation therapy.
• What happens in the treatment room during treatment?Once the treatment position is verified by a physician, the treatment is given. After changing into a gown, the patient enters the treatment room. The patient either lies in the mould or sits in a chair and is fitted with the mask. With laser beams as guides, the patient is moved to a position that is usually within half a centimeter (less than a quarter of an inch) of the calculated optimal position. To make the position more precise, the radiation therapy technologist obtains several low-power diagnostic radiographs or digital images. Distances from various bone landmarks to the isocenter are measured on these daily images. These are compared to identical measurements made on computer-generated films based on the planning CT scan.
Usually, it is necessary to move the patient a few millimeters to make the daily position conform exactly to the prescribed treatment position. These measurements and movements are performed by radiation therapy technologists.
After any necessary movements have been made, the patient's specially-created treatment devices are loaded into the beam line. All of these devices are identified by an individual bar code, which must be scanned by a laser scanner (similar to those found at a supermarket). A match must be made before the computer will permit a treatment to begin. This system minimizes the risk that a patient may be treated with another patient's unique devices.
Next, the technologists and physician retire to a control room to begin treatment. The control room is located just outside of each treatment room. Protons enter the room as a series of discrete spills or pulses which (like x-rays) cannot be seen or felt. After the prescribed radiation dose has been delivered, the computer shuts off the proton beam. The technologists then re-enter the room, and the patient is assisted from the mould or mask and changes out of the gown.
• What is proton radiation?Proton radiation therapy is a form of external-beam radiation treatment. Radiation oncologists (physicians who specialize in radiation treatments) treat in two major ways. One way is by implanting radioactive materials in the body. The other is by using machines to generate beams that penetrate the body from outside. Proton radiation is delivered by the second method. Alternate forms of external-beam radiation therapy include x-ray therapy and Cobalt-60 gamma-ray therapy.
• What makes protons different?Protons, which are positively charged subatomic particles, deposit energy differently than X-ray beams do. Compared to an X-ray beam, a proton beam that is delivered with sufficient energy (or "modulated") has a low "entrance dose" (the dose in front of the tumor). A proton beam also has a high-dose "Bragg peak" region, which is designed to cover the entire tumor. There is no "exit dose" beyond the tumor involved in proton radiation therapy. X-ray beams, by contrast, may deposit most of their dose in tissues in front of the tumor.
More than 41,000 patients around the world have been treated through proton cancer therapy. Because of the number of patients treated and the amount of follow-up data available, we can assess the effectiveness of proton beams for treating cancer. In almost every tumor site examined, the higher tumor doses and lower normal-tissue exposure have improved local control and reduced complications as compared with X-ray therapy. When Medicare and National Cancer Institute (NCI) officials reviewed the available data on proton therapy in the early 1990s, they classified proton radiation therapy as "accepted.” In other words, proton therapy is considered a non-experimental treatment for several localized tumors and for intracranial aneurysms.
Loma Linda University and Harvard University are currently performing studies sponsored by the NCI to determine the optimal proton dose for certain cancers, such as prostate cancer and a variety of brain tumors. These studies do not determine if the treatment is effective. Its effectiveness has already been established. The studies are being done to find out the best ways to use this tool against cancer. Similar studies are performed all the time with other standard forms of cancer therapy, such as chemotherapy and surgery.
• What types of cancer are being treated?Proton radiation therapy is used to treat any cancer or other disease affecting the:
• base of skull
• brain and spinal cord
• head and neck
• chest and abdomen
LLUMC investigators are modifying the synchrotron and proton beam transport system to allow treatment of larger fields, such as those required to for treatment of breast cancer and Hodgkin's disease. We expect this technology to be available in the near future.
• What is the difference between photon and proton radiation?Photon beams make up traditional X-rays, carry a low radiation charge and have a much lower mass than proton beams. Much of photon beams' energy is deposited in the healthy tissue surrounding a tumor due to their low charge and mass causing side effects and unnecessary tissue damage while sometimes not even reaching the tumor with an adequate enough dose.
In contrast, proton beams can be energized to specific speeds or velocities that determine how deeply and where the beams will deliver their radiation. As the proton radiation beams move through the body, they slow down as they interact with orbiting electrons. When the protons have slowed down sufficiently, they release a burst of energy. The physician designs the proton radiation treatment so this burst occurs at the precise site of the cancer, minimizing damage to healthy tissue and reducing side effects.
• Why are there several proton therapy treatments?Proton radiation therapy is commonly given five days a week for several weeks. Normal cells and cancer cells often respond differently to radiation. The normal cells are typically better able to recover from small doses. We give small doses over an extended time period to allow normal cells to recover while inflicting lethal damage on cancer cells.
• Why choose Loma Linda University Medical Center?In operation for over 100 years, LLUMC is home to the most experienced proton treatment center in the world. In addition to the best quality care, Loma Linda’s central location in Southern California means that housing, shopping, dining and places of worship are right within reach.
While at Loma Linda, guests also have access to many of the hospital’s first-rate facilities. One such facility is the Drayson Center, a complete recreation center with tennis courts, swimming pools and other amenities available to guests. On-site cafeterias and restaurants are also accessible.
• Why choose proton therapy?There are many advantages to choosing proton therapy. Completely noninvasive, no cut or incision is made to remove the cancer. This makes it an ideal treatment choice for inoperable tumors and pediatric tumors. The once-daily therapy sessions are also completely painless, and the patient can leave immediately following treatment.
Perhaps most importantly, proton therapy allows patients to live life to the fullest throughout treatment. Because of proton therapy’s accuracy, many of the side effects of radiation treatment can be significantly reduced. This means a much lower chance of side effects such as incontinence or impotence in prostate cancer patients. It also means a return to normal, daily life and activities.