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CACS meeting of 5/18/02 : Meeting summary
Topic: TheraSpheres (a product
replaced in 2003 by SIR-Spheres, which are
made in Australia
Speakers: Dr. Andrew Kennedy, then-assistant professor of medicine at the
University of Maryland School of Medicine and radiation oncologist at the
Cancer Center, and Dr. Galina Tucker, then-protocol coordinator.
Special note: The
TheraSphere study at the
Background on the main speaker. Dr. Kennedy explained that he recently trained with two carcinoid specialists (one of whom was Dr. Larry Kvols) because he had little prior experience with carcinoid patients, and that the carcinoid specialists were interested in turn in trying the TheraSphere treatment. [As of September 2003, Dr. Kennedy had left the University of Maryland medical staff; Dr. Tucker explained that the TheraSphere trial is over although similar treatments are offered elsewhere using SIR-Spheres; she recommended visiting the Sirtex website to find out where (see http://www.sirtex.com/?p=289 ).]
Liver-directed therapies. When surgery is not appropriate, radiation and chemotherapy are other options for treating tumors. External beam radiation is not usually practical for the liver because it is hard to spare normal liver tissue while delivering a lethal dose to the tumors. One can add radioactive materials via surgery to some tumors but only to tumors located on the body’s surface. But there are both radiation and chemo approaches that take advantage of the liver’s unique double blood supply---from both the hepatic artery and the hepatic portal vein---which allows delivery of treatments and in the case of embolization and chemoembolization, blocking of one of these vessels while the other still supplies the normal liver tissue. [See the summary of Dr. Geschwind’s talk on chemoembolization also posted on the CACS website.] Because liver tumors, including neuroendocrine ones like carcinoid, are rather sensitive to radiation as well as to various chemotherapy agents, the hepatic artery can also be used to supply radioactive material to the liver.
The TheraSpheres are basically glass beads or microspheres embedded with yttrium-90, a radioactive element with a short half-life. The yttrium is rolled into the glass, which is fused into spheres in a nuclear reactor using neutron bombardment. This is a 5- to 8-day process. Then the material is shipped, and a dose of about 2 million microspheres is injected into the receiving patient’s hepatic artery Some beads will get stuck on tumors, being too large to pass through them. The radiation is intense but short-acting and goes only a fraction of an inch. An inch away, no radiation is detected.
The tumors have 3x to 10x as many blood vessels as normal liver tissue, so more of the beads get to the tumors than anywhere else in the liver. The researchers have not determined the optimum tumor size as yet, but the tumor needs to be visible on scans. Tiny carcinoid tumors probably do not have enough blood vessels for the TheraSpheres to be effective.
Clinical trials are being done in
The first patient treated with TheraSpheres at UMD had a wonderful response. When a story appeared in U.S. News and World Report, a lot of interest was created. So UMD developed a protocol and got permission to use TheraSpheres in patients meeting a specific set of criteria. The initial plan was to treat 25 patients with all sorts of cancers although the best fit is with patients with just cancer in the liver. The patients who are selected must have good hepatic and hematologic parameters, especially good bilirubin, and no circulatory problems in the liver. They should not have received any prior radiation treatments close to the liver. Then an MRI is done as well as an angiography with a dye. The third patient had 14 visible carcinoid tumors, which all disappeared after TheraSphere treatment.
The researchers found that about 20 of the first 100 patients treated required a small coil to block the TheraSpheres from going to the stomach. (13 of the first 100 patients had carcinoid.) This decision was made by gastrointestinal interventional radiologists using the angiograms and based on the size and pattern of the blood vessels (some would fork to the tumor and some would fork to the stomach too). The coils are made of nonmagnetic material. The area where the coil is becomes unreadable on MRI scans. For 2 individuals, 2 coils were needed.
After 10 to 14 days, the glass beads are no longer radioactive so it does not matter then if some beads gradually escape---but most stay stuck where they first lodged. However, the lungs can be very sensitive and need to be protected; this requires doing an “MAA” imaging test to screen; if 10% could move to the lungs, the individual is not eligible for the TheraSphere procedure.
Procedures for a patient. An interested individual first consults with the medical staff. CT scans are done to anticipate the amount of radiation to infuse. The physics team makes that calculation using an outline of the liver. The patient can choose to be awake for the treatment. Three staff are on the team that does the infusion: a physicist to monitor radiation using a Geiger counter, an interventional radiologist, and a radiation oncologist. Using an angiogram with MAA done the same day, one of the team threads a catheter from the groin into the hepatic artery. Before and after the procedure, a PET scan also is done. FDA also requires a CT scan although Dr. Kennedy says it is useless for these liver tumors because the amount of swelling and shape change is so variable.
This can be an outpatient procedure. Side effects tend to last a few days but can extend for about 2 weeks. There are fewer side effects than for a chemoembolization. The most usual are vomiting, nausea, abdominal pain, and tiredness.
The beads cannot be targeted to specific tumors, and mathematical modeling shows that not all tumors will get the beads. Multiple small infusions may be needed. Besides acting on the tumors, the beads can kill blood vessels that go to the tumors. Among the patients that have been treated two times, not all have gotten their liver functions back to normal yet. Currently no one is treated more than two times. The researchers do not want to cause liver failure.
Some of the carcinoid specialists have referred patients to
UMD for TheraSpheres. Dr. Kennedy thinks
that having the TheraSphere treatment does not rule out being able to try
various other procedures. The TheraSpheres
are used for inoperable liver tumors in patients who have typically already
tried various other treatments, such as chemotherapy, chemoembolization, and
radiofrequency ablation.
Any patients who were on Sandostatin can continue receiving
this medication. Some insurance
companies have approved paying for the procedure in a majority of states. Medicare also has covered it. The cost when UMD was doing it was about
$14,000 per dose, and $28K per procedure.
Some other
One of the members of CACS has had this procedure and is usually willing to talk about it to interested individuals. Please contact the board member on duty to ask about this.
Additional note: a
few internet references. http://www.livercancercenter.upmc.com/AdvancedApproaches/TherasphereBasic.asp
(
http://www.tampabaycancer.com/microspheres.htm
(
http://www.arcweb.tzo.com/arc/arc.nsf/0/828c26864597fbd3c8256af1001558f1?OpenDocument (UMD report at a meeting)