Radiation therapy is a cornerstone of modern cancer treatment. It uses high-energy rays or
particles to destroy or damage cancer cells, preventing them from growing or dividing. While it’s
a powerful tool in the fight against cancer, it’s also one of the most misunderstood. This article
explores the various types of radiation therapy, helping patients and caregivers understand their
options and how each type is chosen.
Broad Classification of Radiation Therapy
Radiation therapy can be broadly classified into three main types:
1. External Beam Radiation Therapy (EBRT)
2. Internal Radiation Therapy (Brachytherapy)
3. Systemic Radiation Therapy
Each type differs in how the radiation is delivered and how it targets the cancer.
1. External Beam Radiation Therapy (EBRT)
This is the most commonly used form of radiation therapy. A machine directs radiation beams at
the tumor from outside the body. Several advanced techniques have evolved to improve
precision and minimize damage to surrounding healthy tissues.
A. 3D Conformal Radiation Therapy (3D-CRT)
3D-CRT uses imaging technologies like CT or MRI scans to map the tumor in three dimensions.
Radiation beams are shaped to match the tumor, ensuring better coverage and sparing normal
tissues.
Indications: Head and neck cancers, lung cancer, prostate cancer, and others.
B. Intensity-Modulated Radiation Therapy (IMRT)
IMRT is a more advanced form of 3D-CRT. It modulates (varies) the intensity of each radiation
beam, delivering higher doses to the tumor while minimizing exposure to nearby organs.
Benefits:
- Reduced side effects
- Improved tumor control
C. Image-Guided Radiation Therapy (IGRT)
IGRT uses imaging (like CT, X-rays, or ultrasound) before or during treatment to ensure accurate
positioning. This is particularly useful for tumors that can shift slightly between sessions, such
as those in the lungs or prostate.
D. Volumetric Modulated Arc Therapy (VMAT)
VMAT is an advanced form of IMRT delivered in a single or multiple arcs around the patient. This
allows faster treatment and precise dose delivery in complex-shaped tumors.
E. Stereotactic Radiosurgery (SRS)
Despite the name, this is a non-surgical treatment. SRS delivers a very high dose of radiation in
a single session to a small, well-defined area—typically in the brain.
Common Uses:
- Brain metastases
- Meningiomas
- Acoustic neuromas
F. Stereotactic Body Radiation Therapy (SBRT)
SBRT (also known as SABR—Stereotactic Ablative Body Radiotherapy) delivers very high doses
over a few sessions (usually 1-5) to tumors outside the brain, such as in the lungs, liver, adrenal
glands, and spine.
G. Proton Beam Therapy
Unlike traditional X-rays, proton therapy uses protons, which deposit most of their energy
directly at the tumor site (Bragg peak) and have minimal exit dose. This makes it ideal for tumors
near critical organs or in children.
Limitations: High cost, limited availability
2. Internal Radiation Therapy (Brachytherapy)
Brachytherapy involves placing radioactive sources directly inside or very close to the tumor.
This allows a high radiation dose to the tumor with minimal exposure to surrounding tissues.
A. Intracavitary Brachytherapy
A device containing radioactive material is placed inside a body cavity, such as the uterus or
vagina.
Common Use: Cervical and endometrial cancers
B. Interstitial Brachytherapy
Radioactive implants are placed directly into the tissue, such as the prostate or breast.
C. High-Dose-Rate (HDR) vs. Low-Dose-Rate (LDR) Brachytherapy
- HDR: Radiation is delivered over minutes. Typically outpatient.
- LDR: Radiation is delivered slowly over several days. Often requires hospitalization.
3. Systemic Radiation Therapy
In this method, radioactive substances are swallowed or injected into the bloodstream. These
substances travel through the body and target cancer cells.
Examples:
- Iodine-131: Used for thyroid cancer after surgery
- Radium-223: Targets bone metastases in prostate cancer
- Lutetium-177 and Actinium-225: Used in targeted radionuclide therapy for
neuroendocrine tumors or prostate cancer
Note: Systemic radiation may require special safety precautions to protect family members and
caregivers.
Choosing the Right Type of Radiation Therapy
The choice of radiation therapy depends on several factors:
- Type and location of the tumor
- Stage and spread of the cancer
- Patient’s general health and preferences
- Proximity to critical organs
- Availability of technology and expertise
A multidisciplinary tumor board—involving radiation oncologists, medical oncologists,
surgeons, and radiologists—often decides the best approach.
Conclusion:
Radiation therapy is not a one-size-fits-all treatment. From highly focused stereotactic
therapies to systemic radioactive medicines, the goal remains the same: to destroy cancer
while protecting healthy tissue. With continuous advancements in technology, radiation therapy
is becoming safer, faster, and more effective than ever before.
If you or your loved one is undergoing radiation therapy, understanding the type being used, can
offer peace of mind and help in making informed decisions.