A feasibility study of [11C]choline for the molecular imaging of human breast cancer in vivo using positron emission tomography (PET)

Abstract

613 Background: [11C]Choline is a novel PET radiotracer. Preclinical studies suggest that it may be promising in breast cancer. [11C]Choline has been recently evaluated as a screening agent in prostate cancer, but no studies have yet investigated its potential in breast cancer. We report a pilot study evaluating the utility and reproducibility of [11C]Choline-PET in breast cancer. Methods: Dynamic imaging was performed on an ECAT962 HR+ PET scanner for 65 min after intravenous injection with 190–369 MBq [11C]choline. Patients with locally advanced and metastatic breast cancer were eligible. All histological subtypes were included (ductal, lobular, and inflammatory). Arterial blood samples were taken continuously for 10 min, with 8 discrete samples up to 60 min to measure [11C]choline and metabolites. Tissue uptake was determined by standardised uptake value at 60 min (SUV, dose and BSA corrected) and Ki (irreversible trapping) calculated using Patlak (corrected for [11C]choline metabolites in plasma) and modified Patlak analysis (corrected for plasma + tissue metabolites). Reproduciblilty scans were performed 2–17 days later in the absence of treatment. Results: Tumour [11C]choline uptake was observed in 10 out of 11 patients (12 out of 13 distinct lesions). There was a significant difference between tumour and normal tissue (breast/lung) in [11C]choline uptake for Ki (p<0.0001) and SUV (p<0.0001). Tissue uptake was of the order lung ≤ normal breast < tumour < liver ≤ spleen. [11C]choline was rapidly metabolised, at 60 min the mean ± S.E. plasma radioactivity due to [11C]choline was 16.4 ± 2.9%. [11C]Choline uptake was found to be reproducible for Ki (modified Patlak: r=0.93, p<0.0001, Patlak: r=0.85, p=0.002) and SUV (r=0.94, p<0.0001) - measured in 8 patients (median of 2 days after the 1st scan). Tumour Patlak Ki was 13.2% > Ki calculated using modified Patlak analysis. Conclusions: [11C]Choline-PET imaging of breast cancer is promising and warrants further evaluation. Tumour [11C]Choline uptake measured by Ki and SUV is reproducible. We plan to study the relationship between choline uptake measured by PET and immunoassays of tumour samples. Functional imaging could have a vital role to determine the efficacy of target-specific agents. No significant financial relationships to disclose.