Reproducibility of [11C]Choline-Positron Emission Tomography and Effect of Trastuzumab

Purpose: This study sought to evaluate the reproducibility of [C-11] choline-positron emission tomography and the effect of trastuzumab in breast cancer. Experimental Design: Twenty-one patients with newly diagnosed and recurrent breast cancer stage II-IV had a baseline dynamic [C-11] choline-PET scan, 10 patients had a second [C-11] choline-PET scan to examine reproducibility, and 6 patients had a second scan within a month after trastuzumab. Analysis of [C-11] choline uptake was measured as the semiquantitative standardized uptake value at 30 and 60 minutes (SUV30 and SUV60), and quantitatively as the net irreversible retention of the radiotracer at steady-state (Ki) and plasma to tissue exchange at 60 minutes (IRF60min). Results: Breast tumor lesions in all patients were visualized by [C-11] choline PET. The difference in tumor versus normal tissue uptake was significant for SUV30, SUV60, Ki, and IRF60 minutes (Wilcoxon P < 0.0001). At 60 minutes postinjection, 15.1 +/- 2.16% of plasma radioactivity was due to unmetabolized [C-11] choline radioactivity. [C-11] Choline uptake was reproducible in breast tumor lesions (r(2) = 0.9 for SUV, 0.9 for Ki, and 0.8 for IRF60). Early responses to trastuzumab measured by [C-11] choline-PET were significant in three lesions occurring in two patients who responded clinically. Conclusions: [C-11] Choline-PET uptake variables can be reproducibly assessed. Initial studies show that trastuzumab decreases [C-11] choline uptake. Clin Cancer Res; 16(16); 4236-45. (C) 2010 AACR.