A Pilot Study of Tc-94m Sestamibi PET MDR Imaging
- A pilot study of PET imaging with Tc-94m sestamibi to assess activity of the multidrug
transporter, MDR-1/P-glycoprotein, an ATP-binding cassette protein that transports drug
out of the cell, thereby reducing intracellular drug accumulation.
- Tariquidar is a safe, nontoxic antagonist of P-glycoprotein. Previous studies
demonstrated that tariquidar increased retention of the radioimaging agent, Tc99
sestamibi in normal liver and in a subset of tumors. These studies were limited by the
semiquantitative nature of total body imaging by conventional radionuclide scintigraphy
- In collaboration with the Clinical Center Nuclear Medicine Department, a PET imaging
agent has been developed, Tc-94m sestamibi, and the FDA has granted approval for its
use in humans.
-To evaluate the feasibility of Tc-94m sestamibi as a PET imaging agent, which should allow
greater resolution and quantitation and thereby make possible direct quantitative
comparisons of tumor uptake before and after treatment with a P-glycoprotein antagonist.
- Patients over 18 years of age, who are eligible for, or have completed enrollment in an
active NCI protocol for treatment of cancer.
- Negative pregnancy test within 24 hrs of Tc-94m injection.
- An index lesion greater than 2cm will be required to optimize the PET images.
- Prior treatment with a P-glycoprotein antagonist is allowed.
- Designed as a feasibility study. Patients meeting the eligibility criteria and signing
informed consent will undergo a PET sestamibi imaging scan in the Department of Nuclear
Medicine. Seventy-two hours later, a dose of tariquidar will be administered before a
repeat imaging study.
- Blood will be obtained for analysis of the pharmacokinetics of Tc-94m sestamibi, and
for isolation of peripheral blood mononuclear cells to assay P-glycoprotein inhibition
in circulating CD56+ cells. These assessments are needed to confirm the impact of
tariquidar on P-glycoprotein in normal cells - for example, those involved in drug
excretion and in circulating mononuclear cells. These results will then be used to
inform the findings in the PET imaging study.
- Fifteen patients will be enrolled and pairwise comparisons will be made between the
sestamibi residence times in tumor, normal liver, kidney, and heart. All comparisons
are noted to be exploratory.
Primary Purpose: Treatment
Determine the feasibility of using PET scanning methodologies with technetium Tc 94m sestamibi.
Susan E Bates, M.D.
National Cancer Institute (NCI)
United States: Federal Government
|National Institutes of Health Clinical Center, 9000 Rockville Pike
|Bethesda, Maryland 20892