What are the types of radiation therapy used for cancer treatment?
Radiation therapy is one of the most common forms of cancer treatment. It uses high-energy X-rays to pinpoint and destroy cancer cells. Radiation damages the cancer cells causing them to stop multiplying.
We asked radiation oncologist Valerie Reed, M.D., to explain some of the most common types of radiation therapy and how they are used. Here’s what she shared.
Some types of radiation therapies are used to treat cancers near sensitive organs.
Four types of radiation therapy are frequently used at MD Anderson when a tumor is close to sensitive organs. These can be used to treat many types of cancer:
3D conformal radiation therapy (3DCRT) uses three-dimensional scans to determine the exact shape and size of the tumor. Radiation beams are shaped by tiny metal leaves arranged to fit the tumor. This minimizes the side effects to healthy tissues. Several cancer types have seen improved outcomes from this including brain cancer, head and neck cancer, liver cancer, lung cancer and prostate cancer.
Image guided radiation therapy (IGRT) tracks the tumor or implanted markers during radiation. This type of radiation treats tumors in areas of the body that move. This includes cancers of the lungs, liver, pancreas and prostate gland, as well as tumors located close to critical organs and tissues.
Intensity modulated radiation therapy (IMRT) delivers multiple radiation beams directly on the tumor. Our team of experts uses special planning software to minimize dose to the surrounding normal tissues. This type of radiation is often used when the tumor is extremely close to surrounding normal organs.
Volumetric modulated arc therapy (VMAT) uses multiple radiation beams of different intensities. As the treatment machine rotates, radiation is delivered at every angle. This focuses the highest dose of radiation on the tumor, while reducing radiation to healthy organs. VMAT can be used to treat several types of solid tumors, including prostate cancer, liver cancer and pancreatic cancer.
Internal radiation therapies use a radioactive source in or near the cancer site
Three common types of internal radiation therapy include:
Brachytherapy involves radioactive material that is implanted in the body. Dozens of tiny “seeds” containing radioactive iodine are placed at the tumor site with a special needle or catheter. This is done as an outpatient procedure. Brachytherapy is used for treatment of prostate, cervical, endometrial, vaginal and breast cancers.
Intraoperative radiation therapy (IORT) is used to treat an exposed tumor during cancer surgery. IORT delivers a high dose of radiation to a surgically exposed treatment area. Surrounding healthy organs and tissues are protected by lead shields. This type of radiation can be used for certain gastrointestinal cancers and other cancers that are challenging to remove during surgery.
Stereotactic radiosurgery (SRS) is not actually surgery. Instead, it uses dozens of tiny radiation beams to treat tumors in the head and neck with a single radiation dose. MD Anderson uses the Gamma Knife® SRS system. Gamma Knife is used to treat cancer that has spread to the brain or head or neck area, as well as tumors in the base of the skull, malignant gliomas, acoustic neuromas, pituitary tumors and meningiomas.
External beam radiation therapies are delivered through a specialized machine directly to the cancer site
These include the following types of radiation therapy:
MRI linear accelerator is used to track soft tissue-based tumors in real time during radiation. During treatment, the MRI is constantly obtaining images. This allows for real-time control of the radiation beam during treatment. This provides the ability to adapt the radiation delivery as needed at each treatment. This technique is used for multiple cancer types with a soft tissue component, such as head and neck cancers and gastrointestinal cancers.