Y90 Therapy in Nuclear Medicine: What You Need to KnowPosted on: 10.31.19 by Digirad
Radioembolization with Y90 is a minimally invasive procedure primarily used in the treatment of liver cancer. In contrast to most nuclear medicine applications, Y90 is therapeutic and designed to treat rather than simply diagnose.
It is estimated that 75% to 95% of patients see improvement from treatment, potentially extending their lives or improving survival rates. In this post we’ll take a look at Y90, what it is, and how it works.
What is Y90?
Yttrium-90 (Y90) is a commonly used isotope within the nuclear medicine and radiation oncology communities for radiation therapy. When used for the treatment, Y90 is relied upon to provide a prescribed amount of radiation to a targeted area. Y90 is most commonly used during a radioembolization therapy, an internal radiation therapy.
Radioembolization using Y90 involves the use of glass or resin beads (spheres) that are filled with the isotope. During a minimally invasive procedure, these radioactive spheres are placed directly into the blood supply of the liver tumor and become lodged within the tumor itself. Blood vessels are blocked off to prevent blood flow (embolization). Once in place, these work by radiating and destroying the surrounding tissue (tumor).
These spheres will remain in the tumor and are not removed. The Y90 has a half-life of 64.2 hours. This means that it will be non-radioactive in about a month’s time.
When is Y90 therapy indicated?
Hepatic (liver) tumors (lesions or masses) may originate as a primary cancer of the liver such as hepatocellular cancer (90% of primary liver cancers) or may be another form of cancer that has metastasized to the region.
There are many treatment options available for hepatic lesions. The choice for treatment is generally based on how they present, physician preference and treatment options available at the facility.
Common non-surgical treatment options for hepatic lesions include chemotherapy (systemic and chemoembolization), ablation (cryoablation, radiofrequency ablation and microwave ablation), embolization (including radioembolization), immunotherapy, and radiation therapy.
Diseases treated with Y90
Currently, the FDA approves the use of Y90 spheres for the treatment of primary hepatocellular carcinoma and unresectable primary colorectal cancer that has metastasized to the liver.
Disease incidence treated with Y90
Based on the available statistics for the United States, it is estimated that 1 in 3,210 individuals annually will be diagnosed with primary colorectal cancer that will metastasize to the liver. Similarly, 1 in 7,675 individuals each year will be diagnosed with primary liver cancer. Annually, this equates to roughly 1 potential Y90 candidate for every 5,442 people.
Y90 mapping and its role with radioembolization therapy
There is a great deal of planning prior to performing a Y90 radioembolization. Here are a few steps:
- The first step in the process is referred to as the “mapping”. The mapping process involves a very similar process to the radioembolization treatment itself; the patient is brought into interventional radiology and the vasculature of the liver tumor is examined. During this time, the interventional radiologist may place coils or perform embolizations; a deliberate blockage of the vasculature to limit the blood flow to and from the intended area of treatment. The blockages are created to direct the delivery of the radioactive spheres and ensure that they lodge in the desired location.
- Once the embolization process is complete, the interventional radiologist will then administer a radioactive particulate that is very similar in size to the Y90. This is performed with a radiopharmaceutical that is commonly referred to as 99Tc-MAA. Once administered, the patient will undergo imaging that utilizes a nuclear medicine gamma camera.Traditionally, this would mean transporting the patient to the nuclear medicine suite post-procedure, however now, mobile cameras (such as the Ergo) can be brought into the interventional suite instead. This offers not only better efficiency but improved safety without the need to transport the patient. The patient doesn’t have to be kept sedated for as long and doesn’t need an anesthesia team to transport with them.
- Images are acquired of the liver and of the lungs and the medical team will perform an analysis of the images. Ideally, the radiologist wants to ensure that 80% or more of the 99Tc-MAA is localized within the liver and does not shunt to the lungs. If more than 20% of the administered mapping dose goes to the lungs, the patient may be required to undergo further embolization to ensure that the Y90 will be directed to the intended location within the tumor.The type of camera used is important. An issue with traditional gamma cameras is that PMTs may miss data on the images. A camera such as the Ergo with its digital technology captures all data without any holes and provides a more accurate picture.
- After the mapping process is complete, the images are further analyzed by the medical team and then an exact amount of Y90 is prescribed to treat the lesion. The entire viability of the therapy depends on quality images and data that are acquired during the mapping process. It is of utmost importance to provide the medical team with the best and most accurate information available.
Patient flow and coding reference guide
Patient precautions and side-effects
The radioembolization procedure is generally painless for patients. For a small number of patients, ulcers may develop in the stomach or duodenum – these are treated as any other type of ulcer.
Post-embolization syndrome (PES) is a side effect that is experienced by a few patients. This consists of vomiting, nausea, fever and pain, usually within the first 72 hours after treatment and subsiding after that. The most common side effect is pain due to the blood supply being cut off to the treated areas. This is controlled via oral or IV medications.
Patients may experience low-grade fever, fatigue and lethargy for up to a week, but most can resume normal activities within a day or two.
As a precaution, the following is recommended:
- Contact with others is limited over the week as the radiation diminishes
- Patients shouldn’t sleep in the same bed as a partner over that week
- Patients should avoid public transport that requires them to sit next to another person for more than two hours
- Patients should avoid close contact with children or pregnant women.
Radioembolization with Y90 utilizes nuclear medicine to treat hepatic lesions. Most patients will see some improvement in their liver and it may improve survival and life expectancy rates, depending on the type of cancer.
This treatment is not recommended in cases of severe kidney or liver dysfunction, abnormal blood clotting or blockages of the bile ducts. Radioembolization may be performed in small amounts over multiple procedures to try to minimize the effects on the liver.