Proton Beam Therapy
Proton beam therapy is a type of radiotherapy that uses a beam of high-energy protons instead of high-energy x-rays (called “photons”) to treat certain types of cancer. Proton beam therapy enables a dose of high-energy protons to be precisely targeted at a tumour, thereby reducing the damage to surrounding healthy tissues and vital organs, which is advantageous in certain patient groups or when the cancer is close to a vital organ.
Proton beam therapy functions by destroying tumor cells and disrupting their DNA. Protons are separated from hydrogen atoms and accelerated in a synchrotron or cyclotron particle accelerator. Using a large magnet, a special device — typically a gantry that can rotate 360 degrees — focuses a stream of protons into a 5 millimeter-wide beam. As the gantry rotates around the patient, the magnet guides the radiation beam and directs it from multiple angles at the tumor. Depending on the depth of the tumor, the proton beam’s energy can be adjusted so that different amounts of radiation can be delivered to different parts of the tumor.
It damages the DNA of the tumor, rendering it incapable of repairing itself or producing new cells. This indicates that the tumor stops growing and begins to shrink. The effects of proton radiation vary based on the size and location of the tumor, among other variables.
Proton therapy is typically used to treat cancer, but it can also be used to treat benign (noncancerous) tumors in children and adults. Proton beams can be used to treat tumors composed of various cell types and located in various parts of the body, including:
– Brain tumors, including those at the base of the skull
– Spinal cord tumors
– Head and neck malignancy
– Ovarian cancer
– Lung cancer
– Thoracic malignancies including thymoma, mesothelioma, and lymphoma
– Liver cancer and metastatic liver tumors
– Pancreatic cancer
– Rectal cancer
– Prostate cancer
– Recurrent tumors that require repeated courses of radiation (reirradiation)
– Sarcomas, including rhabdomyosarcoma
– Eye cancer, such as ocular melanoma
The potential benefits of proton beam therapy for various types of cancer are being investigated.
Proton Therapy Compared to Standard Radiation Therapies
In contrast to traditional photon radiation therapy, which employs X-rays or gamma rays, proton therapy employs proton particle radiation. Both photon and proton radiation damage the DNA of tumor cells, but according to researchers, the damage caused by protons is more direct and difficult to repair. Importantly, protons travel only a limited distance within the body before stopping, and they deliver the highest radiation dose at the end of their path. This energy surge can be represented on a graph as the Bragg peak. Radiation oncologists design proton therapy treatments so that tumor cells receive the maximum dose possible. In this manner, proton therapy reduces radiation exposure and the risk of damaging healthy tissue, particularly in sensitive areas such as the brain, eyes, spinal cord, heart, reproductive organs, major blood vessels, and nerves.
In conventional radiation therapy, such as photon therapy or gamma knife, the beam of high-energy gamma rays or X-rays enters the body, passes through the tumor, and exits the body. Photons emit energy along their entire path, radiating healthy tissue beyond the tumor. 30% to 40% of the photon dose is estimated to pass through the tumor. This “exit dose” of radiation is capable of causing DNA damage to healthy cells. Proton therapy produces almost no exit dose.
While photon and proton radiation may have similar therapeutic effects, the precision of proton therapy makes it a safer option with fewer side effects for certain types of tumors.
Preparation for Proton Beam Therapy
Prior to beginning proton beam therapy, eligible patients are required to attend an evaluation and planning visit at their referred center. Proton beam therapy begins approximately one week later. The tumor’s location and size will be confirmed by CT or MRI scans. The radiation oncologist utilizes these scans to locate and map the tumor’s location, size, and surrounding organs and tissues.
Proton Beam Therapy Procedure
Proton therapy is an outpatient treatment administered in a specialized facility. The majority of patients are treated over the course of multiple sessions, with some treatments requiring more time than others. The proton therapy is administered in a room equipped with a large mechanical arm called a gantry that moves the proton beam around the patient as they lie on a table. A member of the team will create immobilization devices to keep you in the correct position throughout your treatment. The team will create a custom-made mask to keep your head still during head or neck treatment. Radiation oncologists determine targeted radiation doses. The optimal dose, beam position, and body depth are determined by dosimetrists using computer programs. The dose, depth, and angles of the proton beam are examined by physicists to guarantee treatment.
During treatment, the proton beam may turn on and off multiple times as it moves or realigns with the tumor if it shifts as the patient breathes. You will not feel the proton beam entering the body or treating the tumor, but you may hear the machine moving around you.
You can expect to spend 15–30 minutes in the treatment room, depending on the size, location, and number of tumors. The proton radiation treatment itself takes only a few minutes, but it takes additional time to position you and calibrate the machine prior to producing a proton beam. From the time you enter the facility until the time you leave, your entire appointment could take up to an hour.
Adults do not typically require anesthesia (to be put to sleep) during treatment, so they can drive themselves to and from appointments. Children frequently require sedation to help them remain still, so they may need to remain longer following treatment to allow the sedation to wear off.
After receiving proton beam therapy, the majority of patients can return home and resume normal activities. Your doctor may order tests to determine how the treatment is affecting the tumor and make any necessary adjustments. Gradually developing after treatment, side effects may include fatigue or low energy, sore, reddened skin, and hair loss in the treated area.
The majority of patients are treated over the course of multiple sessions, with some treatments requiring more time than others.
Benefits of Proton Beam Therapy
The primary benefit of proton therapy is its ability to deliver higher doses to cancer cells while causing minimal damage to healthy cells. With less healthy tissue affected by radiation, side effects may be milder and the risk of secondary cancers due to radiation is reduced. Due to its precise targeting, proton therapy offers additional advantages:
- Protecting crucial neurological functions such as speech or memory when a tumor is close to the regions that regulate these functions.
- Limiting radiation exposure to vital organs such as the heart and lungs when treating breast or spine cancers.
- Reducing the dangers for children with cancer, who frequently endure permanent side effects from toxic cancer treatments
- Assisting in avoiding additional radiation to previously irradiated areas in the event that a tumor returns close to or in its original location.
- Less serious side effects in comparison to patients who receive traditional radiation
- Proton therapy don’t affect people’s abilities to perform routine activities like housework as much as traditional radiation
