**Internal radiation therapy** and **external beam radiation therapy** are two main approaches to delivering radiation to treat cancer, and they differ primarily in how and where the radiation is applied to the body.
**External beam radiation therapy (EBRT)** involves directing high-energy radiation beams from a machine outside the body toward the tumor. This method is non-invasive and typically performed on an outpatient basis. The radiation passes through the skin and other tissues to reach the tumor, targeting it precisely while minimizing damage to surrounding healthy tissue. Modern EBRT uses advanced technologies such as intensity-modulated radiation therapy (IMRT), which shapes and adjusts the intensity of the beams to conform closely to the tumor’s shape, and image-guided radiation therapy (IGRT), which uses imaging during treatment to improve accuracy. The radiation sources in EBRT can be X-rays, electron beams, proton beams, or neutron beams, depending on the tumor’s location and type. Treatments usually span several sessions over weeks to deliver the total prescribed dose safely[1][3][4][5].
In contrast, **internal radiation therapy**, also known as **brachytherapy**, involves placing radioactive material directly inside or very close to the tumor. This can be done by implanting radioactive seeds, wires, or capsules into the tumor or body cavity near the cancer cells. Because the radiation source is inside the body, the radiation affects a very localized area, delivering a high dose to the tumor while sparing much of the surrounding healthy tissue. Brachytherapy is commonly used for cancers of the cervix, prostate, breast, and head and neck. The radioactive sources may remain in place temporarily or permanently, depending on the treatment plan. This method is minimally invasive but requires specialized procedures to insert the radioactive material[3][4][5].
Key differences between internal and external radiation therapy include:
– **Location of radiation source**: External beam therapy delivers radiation from outside the body, while internal radiation places the source inside or near the tumor.
– **Radiation exposure area**: External beam radiation passes through healthy tissue to reach the tumor, potentially affecting a broader area, whereas internal radiation delivers a concentrated dose to a localized region with less exposure to surrounding tissues.
– **Invasiveness**: External beam therapy is non-invasive, requiring no incisions, while internal radiation involves inserting radioactive material into the body, which is minimally invasive.
– **Treatment duration and sessions**: External beam therapy is typically given in multiple sessions over several weeks, while internal radiation may be delivered in fewer sessions or continuously over a short period, depending on the type of brachytherapy.
– **Suitability**: Internal radiation is often preferred for smaller, well-defined tumors or those located in areas accessible for implantation, whereas external beam therapy can treat larger or deeper tumors and is more versatile for different cancer types and locations.
Both methods aim to destroy cancer cells by damaging their DNA, preventing them from growing and dividing. The choice between internal and external radiation depends on the tumor’s size, location, type, and the patient’s overall condition. Sometimes, both methods are combined to maximize treatment effectiveness.
In summary, external beam radiation therapy uses a machine to send radiation from outside the body to the tumor, while internal radiation therapy places radioactive material inside or near the tumor to deliver radiation directly. Each has unique advantages and applications tailored to different cancer types and treatment goals.