Copper-64 trastuzumab PET imaging: a reproducibility study

BACKGROUND: The current study aims to assess the safety, pharmacokinetics, feasibility, and reproducibility of immuno PET imaging with copper-64 (Cu-64) trastuzumab. METHODS: An IV injection of 296-370 MBq/5 mg Cu-64-trastuzumab was administered between 1 to 4 hours after routine trastuzumab treatment. Whole-body PET scans were performed immediately post-injection and at 24 hours post-injection. Serial pharmacokinetics were performed. Of 11 patients (median age of 52; range of 31-61), 8 underwent a repeat study with Cu-64-trastuzumab to assess image and pharmacokinetic reproducibility. Patients were monitored for toxicity. RESULTS: Patients experienced no allergic reactions or significant adverse effects from Cu-64-trastuzumab. Eight patients successfully completed a repeat Cu-64-trastuzumab study, with acceptable reproducibility of both the biodistribution and pharmacokinetic clearance. Study 1 versus study 2 showed similar serum concentration post-injection (mean 42.4 +/- 7.8 % ID/L vs. 44.7 +/- 12.6 % ID/L) and similar T1/2 (single exponential 46.1 vs. 44.2 hours), P>0.5. The volume of distribution (median 2.50 L) was in the range reported for trastuzumab and close to the estimated plasma volume of 2.60 L. Of 11 patients, two had Cu-64-trastuzumab localization corresponding to known tumor sites - one in liver and one in breast. CONCLUSIONS: Preliminary results suggest that scanning with Cu-64-trastuzumab is feasible, safe, and reproducible. Tumor uptake of Cu-64-trastuzumab was observed, but tumor detection exhibited low sensitivity in this study in which imaging was performed in the presence of trastuzumab therapy.