[18F]galacto-RGD positron emission tomography for imaging of alphavbeta3 expression on the neovasculature in patients with squamous cell carcinoma of the head and neck.

PURPOSE: [(18)F]Galacto-RGD has been developed for positron emission tomography (PET)-imaging of alphavbeta3 expression, a receptor involved in angiogenesis and metastasis. Our aim was to study the feasibility of PET imaging with [(18)F]Galacto-RGD in patients with squamous cell carcinoma of the head and neck (SCCHN).

EXPERIMENTAL DESIGN: Eleven patients with primary diagnosis of SCCHN were examined. After injection of 140 to 200 MBq [(18)F]Galacto-RGD, static emission scans 60 min post injection from the head to the abdomen (n = 11) and dynamic scans >60 min covering the tumor region (n = 6) for kinetic modeling were acquired. Standardized uptake values (SUV) were measured in tumors, muscle and oral mucosa. Immunohistochemistry was done using an alphavbeta3-specific antibody (n = 7). Image fusion with magnetic resonance imaging and/or computed tomography (CT) scans (n = 8) and calculation of tumor subvolumes based on SUVs was done using the iPlan software (BrainLAB).

RESULTS: [(18)F]Galacto-RGD PET identified 10 of 12 tumors, with SUVs ranging from 2.2 to 5.8 (mean, 3.4 +/- 1.2). Two tumors <5 mm were missed. Tumor/blood and tumor/muscle ratios were 2.8 +/- 1.1 and 5.5 +/- 1.6, respectively. Tumor kinetics was consistent with a two-tissue compartmental model with reversible specific binding. Immunohistochemistry confirmed alphavbeta3 expression in all tumors with alphavbeta3 being located on the microvessels in all specimens and additionally on tumor cells in one specimen. Image fusion of [(18)F]Galacto-RGD PET with magnetic resonance imaging/multislice CT and definition of tumor subvolumes was feasible in all cases.

CONCLUSIONS: [(18)F]Galacto-RGD PET allows for specific imaging of alphavbeta3 expression in SCCHN with good contrast. Image fusion and definition of tumor subvolumes is feasible. This technique might be used for the assessment of angiogenesis and for planning and response evaluation of alphavbeta3-targeted therapies.