Sirtex Medical has announced that it has concluded a clinical trial using its proprietary cancer treatment SIR-Spheres and has found them to be safe for use in individuals with kidney cancer. In particular, primary renal cell carcinoma. This trial was the first to use Sirtex’s SIR Spheres outside of their application in treating liver cancer. SIR-Spheres are tiny radioactive beads introduced into the patient’s blood, and utilized to battle cancer from inside the body.

The goal of the trial was to establish overall safety and test if any levels of toxicity existed over 30 days of the treatment regimen. The outcome was a determination that when the SIR-Sphere regimen was administered with no dosage limitation toxicity, there were no recorded serious and/or adverse effects. Of the individuals participating, almost over 5% experienced partial tumor response; almost 90% experienced disease stabilization; and 5% experienced progression of their disease.

How SIR-Spheres work to kill tumors

SIR-Spheres, or Y-90 Resin Microspheres, are a medical device utilized in selective internal radiation therapy (SIRT) for liver tumors. Y-90 Resin microspheres are a permanent implant and for single-use only with a median diameter of 32.5 microns and arrange between 25 and 60 microns.

Y-90 stands for Yttrium-90, which is a high-energy beta emitting isotope. The max range of emission in tissue is a depth of 11mm with a median of 2.5mm, with a half-life of just over 64 hours. After application, 94% of the radiation was received in 11 days. Vis-à-vis these properties, SIR-Spheres Y-90 resin microspheres target point of the microvasculature surrounding the tumor for maximum effect in destroying the tumor but limiting impact on healthy tissue around the tumor.

As applicable to the liver, the SIR-Spheres, which emit radiation via the Y-90, become lodged in the arterioles within the growing rim of the tumor, being too large to pass through. Once lodged there, they deliver radiation directly to the tumor.

Under local anesthetic, an interventional radiologist, trained in administering the SIR-Spheres, guides a micro-catheter to the specified location and administers the SIR-Spheres. The procedure averages 60 to 90 minutes, with a recommended scan to ensure proper placement of the SIR-Spheres.

For more information about SIR-Spheres, visit their web site here.

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