How Is Radiation Given?
Radiation therapy, a cornerstone of cancer treatment, delivers carefully targeted energy to destroy cancer cells and shrink tumors. This energy, in the form of high-energy x-rays, gamma rays, electron beams, protons, or other particles, disrupts the cancer cells’ DNA, preventing them from growing and dividing.
Understanding the Delivery Methods
The method used to administer radiation therapy depends on several factors, including the type, location, and stage of the cancer, as well as the patient’s overall health and other medical conditions. Generally, radiation therapy falls into two main categories: external beam radiation therapy and internal radiation therapy (brachytherapy). A third, less common method involves systemic radiation therapy.
External Beam Radiation Therapy (EBRT)
EBRT is the most common type of radiation therapy. It involves directing beams of radiation from a machine outside the body towards the cancerous area.
- How it works: The patient lies on a table, and a specialized machine, often a linear accelerator (LINAC), precisely aims radiation beams at the tumor. Imaging techniques, such as CT scans, MRI scans, or PET scans, are used to create a detailed 3D image of the tumor and surrounding tissues. This allows the radiation oncologist to meticulously plan the treatment to deliver the maximum dose to the cancer while minimizing damage to healthy tissues.
- Types of EBRT: Several advanced EBRT techniques are available, including:
- 3D Conformal Radiation Therapy (3D-CRT): Shapes the radiation beams to match the tumor’s shape, reducing the amount of radiation that reaches healthy tissues.
- Intensity-Modulated Radiation Therapy (IMRT): Allows the radiation oncologist to adjust the intensity of the radiation beams from different angles, further refining the dose distribution.
- Image-Guided Radiation Therapy (IGRT): Uses imaging techniques to track the tumor’s position during treatment, allowing for real-time adjustments to the radiation beams.
- Stereotactic Radiotherapy (SRT): Delivers high doses of radiation to small, well-defined tumors in one or a few sessions. Can be further divided into Stereotactic Radiosurgery (SRS) when treating tumors in the brain or spine and Stereotactic Body Radiation Therapy (SBRT) when treating tumors in other parts of the body.
- Proton Beam Therapy: Uses protons, instead of x-rays, to deliver radiation. Protons deposit most of their energy at a specific depth, reducing the amount of radiation that passes through healthy tissues.
Internal Radiation Therapy (Brachytherapy)
Brachytherapy involves placing a radioactive source directly inside or near the tumor. This allows for a high dose of radiation to be delivered to the tumor while minimizing exposure to surrounding healthy tissues.
- How it works: The radioactive source, usually in the form of seeds, wires, ribbons, or capsules, is placed inside the body using applicators or catheters. The source emits radiation, killing cancer cells in its immediate vicinity.
- Types of Brachytherapy: Brachytherapy can be administered in different ways:
- High-Dose-Rate (HDR) Brachytherapy: Delivers a high dose of radiation over a short period (minutes or hours). The radioactive source is inserted and removed after each treatment session.
- Low-Dose-Rate (LDR) Brachytherapy: Delivers a low dose of radiation over a longer period (days or weeks). The radioactive source is left in place permanently or temporarily and then removed.
- Permanent Brachytherapy (Seed Implantation): Small radioactive seeds are permanently implanted in the tumor. The seeds gradually release radiation over several weeks or months and eventually become inactive.
Systemic Radiation Therapy
Systemic radiation therapy involves administering radioactive substances that travel through the bloodstream to target cancer cells throughout the body.
- How it works: The radioactive substance can be administered orally (in pill form) or intravenously (through a vein). The substance is selectively absorbed by cancer cells, delivering radiation directly to the tumor.
- Examples of Systemic Radiation Therapy:
- Radioactive Iodine (I-131) Therapy: Used to treat thyroid cancer. The thyroid gland absorbs iodine, so radioactive iodine is specifically targeted to destroy thyroid cancer cells.
- Samarium-153 and Strontium-89: Used to treat bone pain caused by cancer that has spread to the bones.
- Radium-223: Used to treat prostate cancer that has spread to the bones.
Frequently Asked Questions (FAQs)
Here are some frequently asked questions about how radiation is given, to provide a more comprehensive understanding of the process.
FAQ 1: What is a radiation oncologist?
A radiation oncologist is a medical doctor who specializes in using radiation to treat cancer. They are responsible for determining the appropriate type and dose of radiation, planning the treatment, and monitoring the patient’s progress.
FAQ 2: How is the radiation dose determined?
The radiation dose is carefully calculated by the radiation oncologist in collaboration with a medical physicist. The dose is determined based on several factors, including the type, location, and size of the tumor, the patient’s overall health, and the sensitivity of surrounding healthy tissues.
FAQ 3: What is simulation?
Simulation is a crucial step in EBRT planning. It involves using imaging techniques (CT, MRI, PET) to create a detailed map of the tumor and surrounding tissues. This allows the radiation oncologist to precisely target the radiation beams and minimize damage to healthy tissues. During simulation, the patient is positioned in the same way they will be during treatment, and immobilization devices may be used to ensure consistent positioning.
FAQ 4: How long does each radiation treatment take?
The length of each radiation treatment session varies depending on the type of radiation therapy. EBRT sessions typically last 15-30 minutes, including setup and treatment time. Brachytherapy treatment times can range from a few minutes to several days, depending on whether it is HDR or LDR.
FAQ 5: Will I feel anything during radiation treatment?
Most patients do not feel anything during EBRT. However, some patients may experience side effects, such as skin irritation, fatigue, or nausea. Brachytherapy patients may experience discomfort depending on the placement of the radioactive source.
FAQ 6: What are the potential side effects of radiation therapy?
The side effects of radiation therapy vary depending on the treatment area, the dose of radiation, and the individual patient. Common side effects include fatigue, skin changes (redness, dryness, peeling), hair loss in the treated area, nausea, vomiting, and diarrhea. The radiation oncologist will discuss potential side effects with the patient before treatment begins.
FAQ 7: How can I manage side effects during radiation therapy?
Several strategies can help manage side effects during radiation therapy, including medications, dietary changes, skin care, and rest. The radiation oncology team will provide specific recommendations based on the patient’s individual needs.
FAQ 8: Is radiation therapy safe?
Radiation therapy is generally safe when administered by qualified professionals using appropriate techniques. However, it’s crucial to understand that radiation can damage healthy cells as well as cancer cells, leading to side effects. The benefits of radiation therapy in treating cancer usually outweigh the risks, but it’s important to discuss any concerns with the radiation oncologist.
FAQ 9: Can radiation therapy be combined with other cancer treatments?
Yes, radiation therapy is often combined with other cancer treatments, such as surgery, chemotherapy, hormone therapy, or immunotherapy. The combination of treatments depends on the type and stage of cancer, as well as the patient’s overall health.
FAQ 10: What is the role of a medical physicist in radiation therapy?
A medical physicist plays a critical role in radiation therapy. They are responsible for ensuring the accurate delivery of radiation, calibrating the radiation equipment, developing treatment plans, and monitoring radiation safety. They work closely with the radiation oncologist and radiation therapists.
FAQ 11: What are the different types of radioactive materials used in brachytherapy?
The specific radioactive material used in brachytherapy depends on the type of cancer and the desired radiation dose rate. Common radioactive materials include Iridium-192, Cesium-137, Iodine-125, Palladium-103, and Cobalt-60.
FAQ 12: What happens after radiation therapy is completed?
After radiation therapy is completed, patients will typically have follow-up appointments with their radiation oncologist to monitor their progress and manage any long-term side effects. Regular imaging tests may be performed to check for any signs of cancer recurrence. The long-term outlook depends on the type and stage of cancer, as well as the patient’s overall health.