What are SIR-Spheres® Y-90 resin microspheres?

SIR-Spheres Y-90 resin microspheres are microscopic resin beads that contain the radioactive isotope yttrium-90 (Y-90) which emits beta radiation. Due to their small size (average size 32.5 microns) and similar specific gravity to blood cells, the microspheres travel easily through the hepatic artery. The radioactive microspheres become lodged in the tumor microvasculature. Selective Internal Radiation Therapy (SIRT) with SIR-Spheres Y-90 resin microspheres is considered a safe and effective method of using radiation to treat colorectal liver metastases and are often used in conjunction with chemotherapy. SIR-Spheres Y-90 resin microspheres are manufactured by Sirtex Medical Limited which has its headquarters in Sydney, Australia and U.S. operations in Woburn, Massachusetts.

What are the indications for SIR-Spheres Y-90 resin microspheres?

SIR-Spheres Y-90 resin microspheres in combination with intra-hepatic artery chemotherapy (IHAC) using FUDR are the only FDA PMA-approved microspheres for colorectal cancer that has metastasized to the liver. At least 60 percent1 of the nearly 150,000 Americans diagnosed with colorectal cancer every year will see their cancer spread to the liver, and most liver tumors cannot be surgically resected. Metastatic liver cancer is often fatal, with up to 90 percent of patients dying from liver failure. SIRT with SIR-Spheres Y-90 resin microspheres has emerged as a treatment option for patients with colorectal cancer that has spread to the liver.

What do SIR-Spheres Y-90 resin microspheres treat?

SIR-Spheres Y-90 resin microspheres are used to treat metastatic liver cancer, which is one of the deadliest forms of cancer. Colorectal cancer is the second leading cause of death in the United States. The liver is the most common site for the cancer to metastasize or spread. Of the nearly 150,000 Americans diagnosed with colorectal cancer every year, at least 60 percent will see their cancer spread to the liver, and many will die of this disease.1

What is the process for treating patients with SIR-Spheres Y-90 resin microspheres?

SIRT with SIR-Spheres Y-90 resin microspheres is performed as an outpatient procedure by interventional radiologists and requires the placement of a transfemoral microcatheter. Using the liver's unique vascular supply, millions of tiny resin microspheres loaded with yttrium-90 are released into the hepatic circulation. The radioactive microspheres selectively implant in the microvasculature of the tumor where they become lodged. The microspheres emit beta radiation for a period of about two weeks.

The treatment normally takes about 60 to 90 minutes, and after careful monitoring most patients return home four to six hours after the procedure. The reported side effects are few; most patients experience flu-like symptoms for a period of one to three weeks. The procedure can be done concurrently with chemotherapy or as monotherapy.

Is there clinical evidence supporting SIR-Spheres Y-90 resin microspheres for the treatment of patients with inoperable colorectal liver metastases?

There is clinical evidence supporting the use of SIR-Spheres Y-90 resin microspheres in patients with inoperable colorectal liver metastases. SIR-Spheres Y-90 resin microspheres have been investigated together with chemotherapy in 1st and 2nd line setting as well as in a salvage setting in monotherapy or combined with 5-FU.

Where is the procedure performed?

SIRT is performed at a hospital on an outpatient basis by an experienced interventional radiologist who has undergone special training to perform this procedure.

How are SIR-Spheres Y-90 resin microspheres delivered?

During the procedure, an interventional radiologist threads a microcatheter through a femoral artery puncture. The microcatheter is then advanced into the hepatic artery that supplies the liver tumors. Once the catheter is in position, millions of microspheres are delivered directly to the tumor site. The SIR-Spheres Y-90 resin microspheres become lodged in the microvascular tumor bed and emit beta radiation to the tumors, while the surrounding healthy liver tissue remains unaffected.

How do SIR-Spheres Y-90 resin microspheres differ from external beam radiation therapy?

Unlike conventional external beam radiation, SIR-Spheres Y-90 resin microspheres selectively irradiate liver tumors and therefore have the ability to deliver more potent doses of radiation directly to the cancer cells over a longer period.  The tumor-absorbed doses from SIRT are typically 4 to 6 times higher than those to the healthy liver tissue and thereby the therapeutic index of SIRT is significantly higher than external beam radiotherapy.

How common is this procedure?

SIR-Spheres Y-90 resin microspheres are currently being offered at more than 1,230 medical centers around the world, including more than 300 centers in the U.S. Over 92,000 doses of SIR-Spheres Y-90 resin microspheres have been supplied worldwide.

Other than treating the cancer, what are the benefits to the patients?

Besides offering patients an effective treatment option to control the spread of their liver tumors, SIRT also helps patients maintain a good quality of life. The procedure is performed as an outpatient service which minimizes the time spent at the hospital.

What are the potential side effects following SIR-Spheres Y-90 resin microspheres?

Common side effects include abdominal pain or tightness in their abdomen, nausea and loss of appetite which normally subsides within a week.  Patients may also develop a mild fever that may last for up to a week and fatigue which may last for several weeks. As a precaution, specific medications are prescribed to control these symptoms.

What are the potential complications?

In rare instances, a small number of microspheres may inadvertently reach other organs in the body, such as the gallbladder, stomach, intestine or pancreas. If SIR-Spheres Y-90 resin microspheres reach these organs, they may cause inflammation of the gallbladder (cholecystitis), stomach (gastritis) or intestine (duodenitis), and potentially may lead to ulceration. These complications are rare, but if they do occur they require additional medical treatment.

Who is eligible for treatment with SIR-Spheres Y-90 resin microspheres?

The typical patient selection criteria include:

  • Unresectable liver-only or liver-dominant tumors
  • ECOG performance status <2
  • Bilirubin <2 mg/dL
  • Life expectancy >3 months

What precautions should patients take after the procedure?

There are some simple precautions that patients need to take during the first 24 hours following the SIRT procedure. These precautions include: thorough hand washing after using the toilet; cleaning up any spills of body fluids such as blood, urine or stools and disposing of them in the toilet. Otherwise, patients can resume normal contact with family members.

Patients must not receive SIRT treatment if they are pregnant, and must not become pregnant within two months of receiving the treatment as this may cause harm to the unborn baby.

Do medical staff have to take special precautions?

The use of this device is regulated under Title 10 of the Code of Federal Regulations Part 35. These regulations must be followed when handling SIR-Spheres Y-90 resin microspheres.

Does insurance cover the procedure?

Under the terms of the Medicare Prescription Drug Improvement and Modernization Act (MMA) of 2003, Medicare, for the most part, reimburses hospitals for the cost of outpatient treatment with SIR-Spheres Y-90 resin microspheres. Many private payers have recognized the safety and efficacy of the SIR-Spheres Y-90 resin microspheres procedure and as a result have issued positive coverage policies for treatment. A few of these payers include Aetna, Anthem, Cigna, Healthnet, Humana, United Healthcare, Wellpoint and many Independent Blue Cross/Blue Shield plans, as well as other smaller plans on a case by case basis. 

1 Landis SH, Murray T, Bolden S, Wingo PA. Cancer Statistics, 1999. CA Cancer J Clin 1999; 49: 8-31.

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