Therasphere

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Therasphere
Last Updated: February 27, 2009
University of Pittsburgh Medical Center Cancer Center

Therasphere is a therapeutic device that has been approved for use in patients with liver cancer as a Humanitarian Use Device (HUD) by the Federal Drug Administration Office of Orphan Products Development and has been granted a Humanitarian Device Exemption (HDE 980006) for treatment of rare cancers. It was originally developed in 1986 and patented in 1988.

It consists of glass microspheres, mean diameter ranging from 20 (1/5 of 1mm) to 30 microns (or the size of two red blood cells), that are chemically bonded to a radioactive pure beta emitter, Yttrium- 90, that has a physical half life of 64.2 hours (2.68 days). After injection, it produces radiation to tissue with an average range of 2.5 mm and maximum range of less than 1 cm. The Yttrium-90 decays to stable zirconium-90. Each treatment delivers about 150 Gray or 15,000 Rads of radiation to the liver lobe (by contrast, conventional external beam radiotherapy gives about 5,000 Rads). A typical vial of injected Therasphere contains 5 GBq or 135 mCi of radioactivity.

It is currently being used at the Liver Cancer Program of UPMC Cancer Centers and the Thomas E. Starzl Transplantation Institute, for patients who have unresectable hepatocellular carcinoma (HCC or hepatoma). It is delivered to fully conscious patients by a catheter that is inserted into an artery in the groin and delivered directly into the hepatic artery in the interventional vascular radiology suite, under direct monitoring, into either the right or left lobe of the liver. Normally, a one-day hospital stay is needed. Patients typically receive only two treatments to each lobe of the liver. Thus for unilobar tumors only two treatments should be needed; or for bilobar tumors, a maximum of four treatments. Each treatment is given at approximately a two-month interval.

Advantages of Therasphere
It is relatively nontoxic and therefore ideal for patients who have chronic hepatitis or cirrhosis and therefore may not have great hepatic reserve.
Only a limited number of treatments may be needed to achieve the same therapeutic efficacy as multiple treatments with chemotherapy or chemo-embolization (TACE). It is thus cheaper overall than other treatments with limited side-effects.
Therasphere was approved by the University of Pittsburgh Institutional Review Board (IRB) in late 2000, initially for treatment of unresectable HCC. Patients can go home either the same day or the following morning after an overnight hospitalization for safety monitoring. Typically, patients function normally after their treatment and can return to work.

Prior to actual treatment, a volumetric CT scan of the liver is performed to determine the amount of liver volume to be treated, so that the radiation physicist and nuclear medicine physicians can calculate the actual dose of Therasphere that will need to be administered. Additionally, on the day of treatment, an angiogram is performed to check that the artery feeding the liver delivers blood only to the liver and not adjacent branches that might feed other organs such as stomach, pancreas or intestines. Similarly an MAA-Tc-99 (Technetium-99 macro-aggregated albumin) scan is done to check on the day of each treatment that the hepatic arterial flow through the liver does not also extend into the systemic circulation and lungs. This is a rare event and usually does not occur. However, in some patients such "shunting" of blood does occur, especially in severe cirrhosis with portal hypertension and the treatment will need to be aborted, since unacceptable lung radiation could otherwise occur.

At UPMC, Therasphere treatment is given under the guidance of Brian Carr, MD, PhD, FRCP, director of the Liver Cancer Program, medical oncologist to the Liver Transplant Tumor Service and the principal investigator of the study, in collaboration with Dr. Al Zajko, chief of interventional radiology together with nuclear medicine and radiation safety departments, working to ensure that the device is administered appropriately and safely to each patient.

The targeted radiation dose of administered Therasphere for each treatment is scheduled to be approximately 150 Gy of Yttrium-90. Administration is painless. Typically, 135-540 millicuries (mci) of Yttrium-90 (5-10 GBq) are delivered in 10 ml of saline, employing 2-8 million glass microspheres, that are injected over a few minutes into the right or left hepatic artery.

Patients are typically evaluated in clinic once a month thereafter, with regular blood work to examine blood counts and liver function tests and tumor size evaluations by CT scan or MRI of the liver. Since the radioisotope Yttrium-90 is made three to four times a month by the MDS Nordion Company in Ottawa, Canada and has a therapeutically useful life of only seven days, there are certain days each month only when Therasphere can be administered to patients.

Potential risks
Radiation damage to the liver, which is thought to be mild or minimal in patients with excellent liver function; damage to the stomach, pancreas or intestines, if any leakage of the hepatic arterial flow outside the liver occurs; radiation pneumonitis in patients who have severe cirrhosis and portal hypertension, with shunting of blood into the systemic circulation. Given the use of the Tc-99-MAA scan prior to any therapy, the risks seem to be low.

Potential benefits
Tumor shrinkage with minimal damage to the liver and a hoped for prolongation of life after only a limited number of treatments. This therefore may make this a much cheaper therapy than any other current therapy such as intrahepatic chemotherapy or TACE (trans-arterial chemo-embolization) and keep patients out of the hospital with improved quality of life.

Inclusion criteria
Patients with biopsy-proven unresectable HCC, age greater than 18 years and cancer confined to the liver.

Exclusion criteria
Patients with severe cirrhosis, jaundice, metastases, pregnancy or poor renal function or any prior intrahepatic chemotherapy.

Patient evaluation for Therasphere treatment
Patients are evaluated at the Falk Clinic, 4th Floor by the Liver Transplant Tumor Service, which meets each Monday morning. There is never a wait for an appointment. Patients typically arrive with a biopsy report of their tumor type (HCC), CT scan and some recent liver function test blood results.

How to make an appointment
Appointments can be made by calling 412-648-3305 or toll-free at 1-877-640-6746. Ask for the liver tumor coordinators to set up a clinic visit.

©2009 UPMC, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania