Radiation therapy

What is radiation therapy (radiotherapy)?

Radiation therapy — or radiotherapy — is a common cancer treatment that uses radiation (usually high-powered X-rays) to kill cancer cells. Radiation therapy may be used independently or alongside other treatments, like surgery or chemotherapy.

Radiation oncologists are healthcare providers who specialize in radiation therapy. Your radiation oncologist will determine whether radiation therapy would benefit you. If so, they’ll determine the best type of radiation therapy for the kind of cancer you have. They also design the radiation treatment plan with the radiation dosage that will destroy cancer cells without harming nearby healthy tissue.

What are the types of radiation therapy?

There are two main types of radiation therapy: external beam radiation therapy (EBRT) and internal radiation therapy. Both types work by destroying a cancer cell’s DNA. Without DNA instructions telling them to grow and multiply, cancer cells die and tumors shrink.

External beam radiation therapy (EBRT)

External beam radiation therapy (EBRT) is the most common type of radiotherapy. With EBRT, a machine directs beams of high-energy radiation toward the tumor. The energy may be X-rays (most common), electrons or protons. Precision is vital with EBRT. Your radiation oncologist will design a treatment plan to target the tumor with radiation while avoiding your healthy tissue.

There are many forms of EBRT:

• 3D conformal radiation therapy uses CT scans and computer software to create a 3D model of the tumor. Using the model as a guide, the machine directs radiation beams that target the cancer site while sparing healthy tissue.
• Intensity-modulated radiation therapy (IMRT) is a more advanced form of radiation therapy. IMRT uses many radiation beams that vary the dose intensity. It delivers a higher radiation dose to the tumor and lower doses to healthy tissue.
• Arc-based radiotherapy is a form of IMRT. It directs energy beams of varying intensity in a rotational arc-like pattern. This method delivers radiation faster than traditional IMRT. Volumetric modulated arc therapy (VMAT) and tomotherapy are two forms of arc-based radiotherapy.
• Image-guided radiotherapy (IGRT) is a form of EBRT in which the radiation machine obtains a low-dose X-ray or mini CT scan before each treatment. This image helps align the treatment site, resulting in more precise radiation delivery.
• Particle therapy uses radiation therapy that consists of protons instead of photons (X-rays). For certain people, protons can deliver the same radiation dose to the tumor and reduce radiation dose to healthy tissues.
• Stereotactic radiosurgery, such as Gamma Knife surgery, uses high doses of focused radiation to destroy small brain tumors with surgical precision. Unlike surgery, it doesn’t require cutting. Typically, this treatment takes one to five days.
• Stereotactic body radiation therapy (SBRT) uses high doses of focused radiation to destroy tumors outside of your brain. Like stereotactic radiosurgery, it eliminates tumors with surgical precision but without actual surgery.
• Intraoperative radiation (IORT) delivers radiation during surgery. After a tumor has been removed surgically, IORT destroys any remaining cancer cells that aren’t safe to surgically remove.

Internal radiation therapy

Internal radiation therapy places radiation inside of your body, close to cancer cells. It treats smaller tumors in your head, neck, breast, cervix, uterus or prostate.

You can receive internal radiation through a solid source or in liquid form:

• Brachytherapy implants a solid radioactive source, or “seed,” inside or beside a tumor. The source releases radiation to a small area to kill cancer cells. Some implants release low doses for longer periods (weeks). Others may release high doses for shorter periods (minutes). Some implants used in brachytherapy are temporary. Others stay in your body forever. Eventually, they stop releasing radiation.
• Systemic therapy sends liquid radioactive material through your blood to find and destroy cancer cells. Some forms are swallowed. For others, you’ll receive an injection through a vein (IV). Treatments include radionuclide therapy (radioimmunotherapy). With radioimmunotherapy, a radioactive protein recognizes specific cancer cells, attaches to them and then releases radiation to kill them.

Why is radiation therapy used?

Radiation therapy kills cancer cells, shrinks tumors and relieves cancer symptoms. It may be your only treatment, or it may be used to:

• Shrink tumors before other cancer treatments, like surgery (neo-adjuvant therapy).
• Destroy any remaining cancer cells after surgery (adjuvant therapy).
• Kill cancer cells that return after previous treatment.

Radiation therapy can also destroy benign (noncancerous) tumors causing symptoms.