Radiation therapy uses high-energy rays to kill or damage cancer cells.

We use it:

• To shrink tumors before surgery or other treatments
• During surgery for cancers that are hard to remove or kill
• After surgery or other treatments to destroy the remaining cancer cells
• As the main treatment, especially for tumors we can’t take out with surgery
• As a preventive measure to keep cancer from coming back
• To ease symptoms like pain or bleeding in advanced cancer

External beam radiation therapy

External beam radiation therapy (EBRT) is the most common type of radiation treatment. We aim high-energy beams at the tumor from a machine outside the body.  

EBRT does not make you radioactive, so you can safely be around others. It’s less precise than other methods, so it often causes damage to nearby healthy tissue.  

Traditional radiation therapies use X-rays, also called photons.  

• 3D conformal radiation therapy uses imaging scans to plan radiation beams to fit the shape of the tumor. The accuracy allows us to target the tumor with higher radiation doses while sparing healthy tissue.
• Intensity-modulated radiation therapy works similarly but uses many smaller, more focused radiation beams. It can use a higher dose on parts of the tumor.
• Image-guided radiation therapy uses scans taken during the visit. It helps us adjust your position and dose if the tumor has changed. It helps improve accuracy and spare normal tissue.

Instead of using photons, newer types of radiation treatment use proton beams. Protons can reach tumors deep inside the body without scattering radiation. They also stop once they reach the tumor, reducing damage to healthy tissue. Proton therapy is especially useful in children or for tumors near sensitive structures.

Another type of external beam radiation is stereotactic radiosurgery or body radiation therapy. It uses focused, high-energy beams. It's not a surgical procedure and doesn't involve any incisions or cuts.

It may be an option if surgery is too risky for you or if we can’t safely reach the tumor. We use it for tumors in the brain, spinal cord, and central nervous system. For example, we also use it on small tumors with well-defined edges in the liver or lungs.

Internal radiation therapy

Internal radiation therapy, also called brachytherapy, places radiation inside or next to the tumor. It’s common for prostate, cervical, or breast cancer.

There are several types, including:

• Interstitial: We place the radiation sources inside the tumor.
• Intracavity: We place the source within a body cavity, or a cavity created by surgery.
• Episcleral: We attach the source to the eye to treat melanoma there.

The radiation may be in the form of seeds, ribbons, or capsules. To insert the radiation, we use imaging to guide the placement. We can remove the radiation source or leave it in place. Over time, it gets weaker.

Because the seeds stay in for a time, you may be radioactive. So, you need to follow safety precautions around others.

Systemic radiation

Systemic radiation is a medicine that you receive through an IV or orally. The radioactive medicine goes throughout the body. It targets specific tissues based on their chemical makeup or markers on the surface of the cancer cells, so it doesn’t damage healthy tissue.

They contain radioactive elements that release:

• Beta particles: Tiny particles, either negatively charged electrons or positively charged positrons
• Alpha particles: Heavy, highly charged particles made of 2 protons and 2 neutrons, large neutral particles

Types of systemic radiation include: 

• Radioactive iodine for thyroid cancer, hyperthyroidism, or an overactive thyroid
• Radium-223 dichloride for advanced or refractory prostate cancer
• Lutetium-177–dotatate for some rare neuroendocrine tumors in the digestive tract
• Yttrium-90 for liver cancer that has spread or that we can’t remove
• Strontium-89 and Samarium-153 for bone tumor pain

Another type of systemic radiation is total body irradiation. We often use this to prepare for a stem cell transplant. It kills any cancer cells in the body. It also kills the cells in the bone marrow, making room for new blood stem cells to grow.

Positron emission tomography scans use targeted radioactive molecules to find cancer in the body. In a newer treatment called theranostics, a doctor uses these elements to scan for cancer. Then, they turn them into treatments by swapping in stronger radioactive elements to kill the cancer cells.

If the cancer “lights up” on the initial scan, the therapy will also go to the right place. This way, the medicine finds the tumor cells and delivers the radiation directly to them.

Your radiation oncologist will review your case and explain whether radiation is part of your cancer care plan. They’ll talk to you about how to prepare for radiotherapy. Preparations will include imaging scans.

For external radiation therapy, you may have a mask or mold made to target your treatment. You will have multiple short sessions over several weeks.

You may have just one procedure to place the seeds for internal therapy. For systemic radiation, you may need to limit contact with others to reduce their exposure to radiation.