Reproducibility of [11C]choline-positron emission tomography and effect of trastuzumab.

PURPOSE

This study sought to evaluate the reproducibility of [(11)C]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 [(11)C]choline-PET scan, 10 patients had a second [(11)C]choline-PET scan to examine reproducibility, and 6 patients had a second scan within a month after trastuzumab. Analysis of [(11)C]choline uptake was measured as the semiquantitative standardized uptake value at 30 and 60 minutes (SUV(30) and SUV(60)), 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 [(11)C]choline PET. The difference in tumor versus normal tissue uptake was significant for SUV(30), SUV(60), Ki, and IRF60 minutes (Wilcoxon P < 0.0001). At 60 minutes postinjection, 15.1 +/- 2.16% of plasma radioactivity was due to unmetabolized [(11)C]choline radioactivity. [(11)C]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 [(11)C]choline-PET were significant in three lesions occurring in two patients who responded clinically.

CONCLUSIONS

[(11)C]Choline-PET uptake variables can be reproducibly assessed. Initial studies show that trastuzumab decreases [(11)C]choline uptake.