Lab Works

CONTEXT: Interest in targeted cancer therapies has prompted a search for more specific tracers. Data presented at the 2006 Society for Molecular Imaging meeting in Hawaii in September by Dr. Ambros Beer from the Technical University of Munich, Germany, highlights the potential of F-18 galacto-RGD, a PET probe targeted at avb3 integrin, a glycoprotein associated with angiogenesis and tumor metastasis.

RESULTS: Beer presented two studies: one focusing on invasive ductal breast cancer and the other testing the relevance of galacto-RGD in examining head and neck cancers. Twelve patients with invasive ductal breast cancer underwent imaging with F-18 galacto-RGD PET. Head-to-abdomen scans were performed on all patients 60 minutes after injection, and dynamic scans over the tumor region were performed for eight patients. PET performed with the investigation tracer identified all invasive cancers with standardized uptake values ranging from 1.4 to 8.7. Immunohistochemistry confirmed avb3 expression in all tumors, with avb3 located on microvessels and tumor cells.

For the head and neck study, Beer and colleagues performed head-to-abdomen scanning on 10 patients and dynamic scanning after F-18 galacto-RGD injection over the tumor region of six patients with known disease. Tracer uptake was observed in eight of 10 head and neck tumors with SUVs ranging from 2.2 to 5.8 but not in two > 5 mm tumors. Immunohistochemistry confirmed avb3 expression on microvessels in all seven specimens tested and in one specimen of tumor cells that was tested.

IMAGE: F-18-galacto RGD PET (A) and fusion image with T1-weighted MRI (B) show intense tracer uptake in left tumor of patient with two squamous cell oral cavity carcinomas. Right tumor shows moderate tracer uptake (arrows). Immunohistochemistry of avb3 expression (C) shows tumor vessel staining (arrow).

IMPLICATIONS: Initial results suggest that F-18-galacto RGD could be used to monitor anti-angiogenic therapies in head and neck cancer, Beer said. The Technical University of Munich group plans further studies in breast cancer, where avb3 expression is more complex.

F-18-galacto RGD PET of patients receiving anti-angiogenic drugs and combination chemotherapy regimens will be correlated with conventional imaging methods of monitoring angiogenesis. The tracer could also be used to preselect patients in trials of anti-avb3 drugs, Beer said.