Yttrium-90 (90Y) RadioMicrosphere Therapy

June 16, 2010 (Salt Lake City, Utah) — Scintigraphy using single
photon emission computed tomography with an integrated x-ray computed
tomography scanner (SPECT/CT) to detect extrahepatic shunting could
help boost the safety of yttrium-90 (90Y) radiomicrosphere therapy in
the liver, according to a Cleveland Clinic study presented here at the
Society of Nuclear Medicine (SNM) 2010 Annual Meeting.

Microsphere technology has gained popularity among surgeons and
interventional radiologists as an effective organ-preserving method of
individually treating hepatic malignancies, noted lead investigator
and presenter Ron Young, technologist and manager of the nuclear
medicine department at the Cleveland Clinic in Ohio.

Mr. Young described how, in a typical procedure, the 20 to 40 μm glass
spheres imbedded with 90Y are injected into hepatic artery circulation
where they selectively embolize the tumor's microvasculature. Beta
particles emitted by the isotope kill cells in a 2.4 mm diameter
region around the tumor and spare healthy liver tissue.

Hepatic radiomicrosphere therapy is considered safe, with a
complication rate of less than 5%, Mr. Young reported. But he added
that many adverse events arise from the incomplete embolization of the
hepatic vessels under angiographic guidance before the procedure. It
can lead to severe pulmonary, gastrointestinal, and pancreatic
radiation burns after the 90Y particles are shunted from the liver.
Other complications include pancreatitis, cholestitis, and gastritis,
he told Medscape Radiology in an interview.

To minimize risk, technetium-99m (99mTc) microaggregated albumin (MAA)
imaging is performed to simulate extrahepatic shunting in the presence
of incomplete hepatic vessel embolization before the surgeon moves on
to the actual procedure, Mr. Young explained.

With guidance from staff interventional radiologist Abraham Levitin,
MD, Mr. Young and colleagues found that 99mTc-MAA SPECT/CT was 2.5
times more accurate than planar imaging in this role.

In 99 consecutive patients who underwent both imaging procedures,
extrahepatic shunting was detected in 23 patients with SPECT/CT and in
9 patients with the planar approach. The investigators did not perform
a detailed statistical analysis.

SPECT/CT also detected a hepatic thrombosis that was not observed on
planar images, Mr. Young noted. The finding led the surgical team to
minimize the lumen of the thrombosis in the inferior vena cava before
turning their attention back to liver treatment, he added.

The findings promise a significant improvement over the standard
technology, said Peter S. Conti, MD, professor of radiology, pharmacy,
and biomedical engineering at the University of Southern California in
Los Angeles. Dr. Conti was not involved with the study.

"The broader implications are that the use of SPECT/CT improves the
ability of the clinician to determine if patients are good candidates
for therapy," he said during an SNM-sponsored media briefing.

Hooman Kabiri, MD, who performs 90Y microsphere procedures at the Ohio
State University Medical Center in Columbus, said in a phone interview
that a shift to SPECT/CT would give him and other interventionist
radiologists more peace of mind.

"It can add to the sensitivity of detecting our ability to embolize
the communications between the hepatic and nonhepatic arteries. It is
a valuable tool in that respect," he told Medscape Radiology.

But shifting to SPECT/CT could also lead to unnecessary treatment
delays because of possible false positives, he cautioned. The 3%
adverse incident rate at Ohio State suggests that the actual rate of
extrahepatic shunting is much lower than the 23% rate identified with
SPECT/CT in the Cleveland Clinic study, he said about the trial.

A larger prospective study testing the relative clinical efficacy and
accuracy of the 2 imaging techniques is planned, Mr. Young told SNM
meeting attendees.

The study did not receive commercial support. Mr. Young, Dr. Conti,
and Dr. Kabiri have disclosed no relevant financial relationships.

Society of Nuclear Medicine (SNM) 2010 Annual Meeting: Abstract 2023.
Presented June 7, 2010.