Radioembolization or Selective Internal Radiation Therapy (SIRT)
Radioembolization is a new, minimally invasive procedure which allows doctors to deliver radiation therapy specifically and directly into liver tumors. Although originally thought to embolize, or block off, arteries feeding the vessel (hence the name radioembolization), the Y-90 radiation particles delivered are so small that they lodge directly into the tumors, leading the arteries open. This novel treatment is performed entirely through a tiny nick in the skin, and patients go home hours after the procedure is done.
Who is a candidate for the treatment?
This is a treatment for patients who have predominantly liver tumors and who are not good candidates for surgical removal. Although originally FDA-approved for liver metastases spreading from colon cancer, it has been approved and is used for numerous other cancers which originate or spread to the liver. The most common cancers treated by Y-90 include metastatic colorectal cancer, hepatocellular liver cancer (HCC), and neuroendocrine liver metastases. For most patients, this type of treatment is not meant to be curative; treatment goals include local disease control, downstaging to allow for surgery, bridging to transplantation, and extending survival.
How should I prepare?
Several days before the procedure, you will have an office consultation with the interventional radiologist and staff who will perform your procedure. Here, the procedure and background are explained in depth, and a discussion is had if this is the correct procedure for you. All of your questions will be answered and you will receive literature to help you understand this treatment.
We will also do a complete history and physical at this consultation. You should report to your doctor all medications that you are taking, including herbal supplements, and if you have any allergies, especially to local anesthetic medications, general anesthesia, or to contrast materials containing iodine (sometimes referred to as “dye” or “x-ray dye”). It is very important for us to know what chemotherapy and radiation treatments you have previously undergone, and when.
Prior to your procedure, your blood will be tested to determine how well your kidneys are functioning and whether your blood clots normally. You will also have a special type of CT known as a CTA or CT Angiogram. This CT shows us the extent of your tumor, allows us to accurately analyze the size (volume) of tumor, and allows us to map out the anatomy of your vessels.
You will be given a sedative during the procedure days. You will receive specific instructions on eating and drinking before the procedure and will need to have a relative or friend accompany you and drive you home afterward.
How does the procedure work?
Once you are deemed an appropriate candidate for this procedure, you will schedule days that are convenient to you. The overall procedure actually takes place on two or three separate days. On the first day, a procedure called the “mapping angiogram and shunt embolization” is conducted and can be considered a test run. Weeks later, the subsequent procedure day or days entail the actual injection of the radiation particles into the liver. As only one half of the liver is treated at a time, some patients who need injections into both sides of the liver may return for two procedures. None of the procedures generally lasts longer than 90 minutes and patients almost always go home the same day, only a few hours later.
Step 1: Mapping Angiogram and Shunt Embolization
This day will be the preparation day for the actual treatment. After you arrive in the interventional radiology holding area, you will be prepped by the nurses for the procedure. The procedure itself takes place in a room called an interventional radiology (IR) suite. It looks very similar to an operating room, except that there is a large C-shaped machine located next to the bed. If x-rays were photographs, this machine allows us to shoot the equivalent of movies once contrast is injected (called angiograms).
Once in the room, you will be given medication called moderate sedation. This type of sedation uses a combination of medications to make you feel sleepy and drowsy while killing pain. Although you will be arousable, most patients tend to sleep or remain drowsy throughout the procedure. The reason we need you to be arousable is so that you can hold your breath for the few angiograms we perform, otherwise we would get a blurry movie due to the breathing motion.
Once you are sedated, the interventional radiologist numbs the skin in the groin with lidocaine and gently inserts a catheter, or tube, into the artery and advances it carefully towards the liver.
Multiple angiograms, or maps, of your blood vessels leading to and inside the liver are obtained. At this point, it is critical to block any extra pathways (called shunts) that could potentially allow the radiation particles to travel in a non-target direction back toward the stomach. Blocking of these shunts is called embolization, and there are generally two vessels which are commonly blocked – the gastroduodenal artery (GDA) and the right gastric artery. As there are multiple pathways of flow called collaterals – think detours around a closed street – embolization of these vessels is tolerated easily by the body.
After the shunt embolization, the interventional radiologist will inject particles to do a ‘test run’. The particles that are injected are called MAA particles, and they are chosen for two simple reasons – they are almost exactly the same size and shape of the Y-90 spheres (and therefore mimic them very well), and they can be easily tagged to see where they go. So finally, after the MAA particles are injected, the patient goes to have a “perfusion scan” in nuclear medicine. This hopefully will show most, if not all, of the particles staying in the liver and not accidentally travelling towards the stomach or lungs. This is crucial to know, as unwanted radiation particles in the stomach can cause severe ulcers and bleeding, while unwanted radiation particles in the lungs can cause radiation fibrosis.
Step 2: Y-90 Radioembolization
Once the mapping angiogram and shunt embolization is done, we will know for sure if it is safe to inject the Y-90 particles based on your “test run”. You will be called within a few days thereafter to schedule the actual Y-90 injection procedure days. Y-90 treatment is only done to one half of the liver (lobe of the liver) at a time, so if there are tumors in both lobes of your liver you will be scheduled for two separate injection days.
The Y-90 injection procedure days are generally much quicker than the mapping angiogram days. Just like the first mapping angiogram day, you will be brought into the IR suite. After sedation, the tiny catheter will again be placed in your liver arteries leading towards the tumor(s). The radiation-filled microspheres, or resin beads, are then slowly, carefully, and deliberately injected through a microcatheter into the arteries feeding the tumor.
SIR-Spheres® microspheres treatment, offered at Rochester General Hospital, is a targeted radiation therapy that delivers a dose of internal radiation up to 40 times higher than conventional external beam therapy while sparing healthy tissue. This maximizes the treatment’s effectiveness and reduces the risk of injury to the liver. SIR-Spheres microspheres are FDA PMA approved for patients with inoperable metastatic colorectal cancer to the liver.*
- SIR-Spheres microspheres are released into the arterial blood supply and carried directly to the tumor.
Once the microspheres lodge at the tumor site, they deliver a high dosage of radiation directly to the cancer cells. Advantages over direct radiation therapy including being able to give higher doses of lethal radiation to the tumor while sparing surrounding normal liver tissue. The microspheres will block the flow of blood to the tiniest vessels in the tumor, depriving the diseased cells of the oxygen and nutrients needed to grow. The radiation from yttrium-90 continually decreases over a two-week period and disappears after 30 days. The tiny microspheres remain in the liver without causing any problems.
Radioembolization is generally painless, however some patients may experience brief pain when the microspheres are injected. The procedure is usually completed within ninety minutes and is most often conducted on an outpatient basis.
Clinical trials have shown that the use of SIR-Spheres® microspheres treatment increases the time-to-disease progression and overall survival without adversely affecting the patient’s quality of life.12 In clinical studies, SIR-Spheres microspheres have been combined with modern chemotherapy or administered as a monotherapy during a chemotherapy holiday and have been proven to: 2-9
Decrease the tumor burden in the liver
Increase time-to-disease progression
Increase survival time11
- Increase time-to-disease progression 2,3
- Potentially downsize tumors to liver resection or ablation 2,4,8,9
- Provide palliation of symptoms
What will I experience after the procedure?
Few patients experience some side effects called post-embolization syndrome, including nausea, vomiting, abdominal pain and cramping, and fever. Pain and fatigue are the most common side effects that occur because the blood supply to the treated area is cut off. It can readily be controlled by medications given by mouth.
These side effects usually subside within three to five days and may be alleviated with medication. You should tell your doctor if these symptoms last more than seven to ten days.
You may also experience a low-grade fever, lethargy and fatigue that usually last about one week.
You should be able to resume normal activities within a day or two following the procedure.
During the week following your radioembolization, you will need to limit contact with others while the radiation in your body diminishes. You should not do the following for at least seven days after the procedure:
sleep in the same bed as your partner.
- use public transportation that requires you to sit next to another person for more than two hours.
- come in close contact with children or pregnant women.
CT scans or MRI may be performed every three months following the treatment to determine the size of the treated tumor.
Who interprets the results and how do I get them?
The interventional radiologist can advise you as to whether the procedure was a technical success when it is completed. Your interventional radiologist may recommend a follow-up visit after your procedure or treatment is complete. Your plan will be discussed between your interventional radiologist and your oncologist, radiation oncologist, and/or surgeon.
What are the limitations of Radioembolization?
Radioembolization is not recommended in cases of severe liver or kidney dysfunction, abnormal blood clotting, or blockage of the bile ducts. In some cases, despite liver dysfunction, radioembolization may be done in small amounts and in several procedures to try and minimize the effect on the normal liver. Prior liver radiation may preclude Y-90 treatment.
Radioembolization is a treatment, not a cure. Approximately 70 to 95 percent of the patients will see improvement in the liver and, depending on the type of liver cancer, it may improve survival rates. Multiple studies show that up to 95 percent of patients with colorectal metastases (tumors that have spread) and up to 97 percent of patients with neuroendocrine tumors benefit from radioembolization.
SIR-Spheres® is a registered trademark of Sirtex SIR-Spheres Pty Ltd.
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