Internal Radiation 101: A Guide to Your Treatment

Internal Radiation 101: A Guide to Your Treatment

Reviewed by Jasper Clinical Board

Last updated 5/24/21

What is internal radiation therapy?

Radiation is a type of energy that can kill cancer cells if used correctly. Modern medicine has developed incredibly precise and effective ways to do exactly that—targeting cancerous tumors while keeping your healthy body tissues protected. 
External radiation therapy” means the source of this radiation is outside of your body. In other words, a large medical device (like an X-ray machine) shoots a powerful beam of radiation right through you to target the tumor. But with internal radiation therapy, the radiation source is positioned inside you—either as a radioactive implant, or via medication that’s swallowed or injected.
Internal radiation therapy is sometimes used on its own, and sometimes combined with other forms of cancer treatment. That can include external radiation therapy, chemotherapy, and more.

What are the different types of internal radiation therapy?


One of the most sophisticated and precise forms of radiation therapy is called brachytherapy. This involves placing a radioactive implant in or near your cancer. The implant slowly releases radiation, killing the cancer while minimizing your overall radiation exposure. (Radiation can damage healthy cells as well as cancerous ones, so this is a huge benefit.)
To guide your treatment, the surgical team will use imaging technology (like X-rays and CT scans) to pinpoint the right place for an implant. They’ll then insert one or several implants (often called “seeds” or “pellets”), which are typically smaller than a grain of rice. Each implant is made of a radioactive material like palladium-103 or iridium-192 surrounded by a metal casing. They’ll be placed in a natural body cavity (like the uterus or rectum) or directly in your body tissues.
Depending on your situation, your healthcare team may opt for a temporary implant or a permanent one. Temporary implants are removed after they do their work, while permanent implants quickly release all of their radioactive energy and are perfectly safe to keep in your body. 
Your team will also help you choose between low dose-rate therapy (LDR) and high dose-rate therapy (HDR). LDR delivers a low dose of radiation over one or several days, during which you’ll probably stay in the hospital. HDR, on the other hand, delivers short, powerful bursts of radiation (think 10-20 minutes) using strong temporary implants. This can typically be performed as an outpatient procedure (no hospital overnights!), which is more convenient and cost-effective.
Note that you may need to make small lifestyle adjustments during your treatment to avoid exposing other people to radiation. Be sure to discuss this with your healthcare team!

Systemic radiation therapy

Sometimes the best way to target cancer is to take a radioactive medication that washes through your whole body and collects at the problem area. This is called systemic radiation therapy (SRT), or radioisotope therapy. 
Because this treatment relies on your body’s natural processes to deliver the drug, it only works on certain types of cancer. For example, if you have thyroid cancer, you’ll be given a radioactive form of iodine (technically called an isotope) to drink. The medication gathers in your thyroid, where it goes to work killing cancer cells until your body naturally excretes it. Systemic therapy can also be used to treat bone and prostate cancer.
When you get SRT, the radioactive medication may be delivered as an injection, or it may be given as a drink or capsules to swallow. The healthcare team that gives you this medicine will take precautions to stay safe, like wearing protective gear and bringing you to a special isolation room for treatment. You may be able to leave shortly after treatment, or you may have to stay overnight for other people’s safety.
It’s important to understand that systemic radiation therapy makes your body radioactive for a few days. To keep other people safe during this time, you’ll need to protect them from contact with your urine, saliva, sweat, and other bodily fluids. You may also need to avoid contact entirely with certain people (like children and pregnant women), avoid public transit, and take other special measures if you share your home. 
Don’t worry - your healthcare team will make sure you know these details before you leave the hospital! Read more here about radiation therapy and other people’s safety.

What are the major steps of treatment?


Step 1: Consultation

To get started, you’ll have a consultation with your radiation oncologist. This doctor is your go-to specialist for the radiation therapy experience. They’ll be with you every step of the way, so get comfortable with them and feel free to ask questions! 
At this first appointment, your radiation oncologist (and perhaps other healthcare providers on your team, like a radiation oncology nurse) will take a full assessment of your health. They’ll also review any images of your cancer (such as X-rays or ultrasounds) and perhaps run some other tests. The goal of this consultation is to come up with your unique plan for cancer treatment.

Step 2: Simulation

This next step is only necessary for some types of internal radiation therapy. The purpose of a simulation (aka SIM) appointment is to get everything prepared so your actual treatment goes smoothly. You won’t receive any actual radiation on this day. Instead, your healthcare team may take additional scans (often CT scans) to precisely locate your cancer. This will help them guide your brachytherapy implant to exactly the right place.
Your team may also want to measure you for an immobilization device. This can be a mold, cast, or belt that helps you stay in the same position for every treatment session. For high dose-rate treatments (where a powerful implant is placed and then removed multiple times), this is crucial. It ensures your implant always ends up in the ideal place—i.e. down to the millimeter—to treat your cancer and minimize side-effects. Read more here about simulation appointments.

Step 3: Treatment

As we mentioned above, there are many different types of internal radiation therapy with different courses and timelines. Your treatment may last several days or several weeks. It may involve overnight hospital stays, or you may be treated as an outpatient—i.e. visiting the hospital for a few hours at a time. 
We know the uncertainty around these issues can be difficult, but try to not to stress. The sooner you have your initial consultation, the sooner you’ll have a treatment timeline that you can plan around.

Side effects & self care

The most important thing you can do during internal radiation therapy is to carefully track your symptoms and report any changes to your healthcare team. If you think a symptom is too small or silly to mention, it’s not! Your doctor really does want to know everything—and even minor-seeming problems (like dry mouth) can be improved and kept from progressing to bigger problems if you speak up early. This is true whether you’re getting brachytherapy, systemic radiation therapy, or a less conventional form of internal radiation treatment. 
There will almost certainly be some side effects from your treatment. Fatigue is especially common, with over 80% of cancer patients experiencing it, so now is a great time to get prepared. Talk with friends, family members, and other caregivers about how they can help you manage fatigue and other issues. Driving, grocery shopping, scheduling, dealing with insurance companies, and countless other small tasks will be much easier with a team.
Beyond fatigue, you’ll probably notice other side effects which will depend largely on where your cancer is located. For instance, if you’re getting prostate cancer treatment, you may experience some urinary and sexual symptoms. For head and neck cancer treatment, on the other hand, you may have mouth sores and trouble eating. Just ask your healthcare team what to expect, and they’ll help you get prepared. 
Finally, you may want to explore wellness practices like yoga, meditation, and relaxation breathing techniques. Research has shown that they may be promising for your overall health outcomes. And just as important, they can help you cope with the emotional and physical stress of cancer treatment. Internal radiation therapy may be a challenging time, but even small steps like these can make your experience easier, happier, and healthier.

The content on this website is intended to provide the best possible information for you, but should not be considered—or used as a substitute for—medical advice. If you have questions about your diagnosis or treatment, please contact your health care provider(s). For questions or comments about this content, please email us at