Initial Experience of Monitoring Response of Breast Cancer to Bevacizumab-containing Chemotherapy using A New Integrin Specific PET Imaging Tracer [F-18]RGD-K5

Abstract

This study investigates the use of [F-18]RGD-K5, an integrin αvβ3 targeting PET tracer, in breast cancer patients receiving chemotherapy with bevacizumab (Avastin®). Two patients were analyzed: Subject-1 had metastatic breast cancers and Subject-2 had a primary cancer in the breast. The therapy regimen was weekly paclitaxel and carboplatin combined with bi-weekly bevacizumab. Each subject received 5 PET-CT scans: pre-treatment [F-18]RGD-K5 and [F-18]FDG, one [F-18]RGD-K5 F/U scan after 2 doses of bevacizumab, and another [F-18]RGD-K5 and [F-18] FDG F/U after 4 doses of bevacizumab. Many lesions in Subject-1 showed a high [F-18]RGD-K5 baseline uptake. The two most [F-18]RGD-K5 avid lesions had SUVs of 10.8 and 10.1, and the corresponding [F-18]FDG uptakes were much lower (SUV of 1.0 and 3.5). The [F-18]RGD-K5 SUVs in all analyzed lesions decreased during treatment, showing a mean of 34% reduction after 2 doses, and 47% reduction after 4 doses of bevacizumab. The changes in the [F-18]FDG SUVs were much smaller, with a mean reduction of 24%. In contrast to the patient with metastatic cancer, the primary tumor in Subject-2 showed a low [F-18]RGD-K5 uptake (SUV=1.8), but a high [F-18]FDG uptake (SUV=8.7). The [F-18]FDG SUV decreased to 2.4 (72% reduction) after 4 doses of bevacizumab, while the [F-18] RGD-K5 uptake remained unchanged. The results that [F-18]RGD-K5 avid lesions show a great SUV reduction after bevacizumab treatment suggest that the [F-18]RGD-K5 tracer may be potentially used for selecting candidate patient for receiving bevacizumab, as well as in monitoring of the early treatment changes.