Abstract
A novel radio guided surgery (RGS) technique exploiting β- radiation has been proposed. To develop such technique, a suitable radio-tracer able to deliver a β- emitter to the tumor has to be identified. A first candidate is represented by 90Y-labeled [1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid0-D-Phe1,Tyr3]octreotide (DOTATOC), a compound commonly used today for peptide radio-receptor therapy. The application of this β- -RGS to neuroendocrine tumors (NET) requires to study the uptake of DOTATOC and its time evolution both in tumors and healthy organs, and to evaluate the corresponding performances of the technique. Methods: the uptake of lesions and healthy organs (kidneys, spleen, liver and healthy muscle) was estimated on 177Lu-DOTATOC SPECT/CT scans of 15 patients affected by NET with different localizations, treated at IRCCS-Arcispedale Santa Maria Nuova, Reggio Emilia, Italy. For each patient SPECT/CT images, acquired at 0.5, 4, 20, 40 and 70~hours after injection, were studied. For each lesion the Tumor Non Tumor Ratio (TNR) with respect to all healthy organs and its time evolution were studied. A subset of the patients showing hepatic lesions was selected, and the TNR with respect to the nearby healthy tissue was calculated. By means of a Monte Carlo simulation of the probe for beta- -RGS, the activity that is to be administered for a successful detection was estimated lesion-by-lesion. Results: the uptake of DOTATOC on NETs showed a maximum at about 24hours after injection. The cases of hepatic lesions showed TNR values compatible with the application of beta- -RGS. In particular, 0.1 ml residuals are expected to be detectable within 1s with 5% false-negative and 1% false-positive by administering the patient as little as 1MBq/kg. Conclusion: the balance between tumor uptake and metabolic washout in healthy tissue causes the TNR to increase with time, reaching its maximum after 24 hours and this can be exploited when using a radio-tracer with long half-life as 90Y. In particular, in case 90Y-DOTATOC is used with liver NET metastases, the here proposed RGS technique is estimated to be feasible by injecting an activity that is one third of the one commonly used for PET imaging.
- Oncology: Endocrine
- Oncology: GI
- Radiotracer Tissue Kinetics
- DOTATOC uptake
- beta- radiation
- neuroendocrine tumors
- radio guided surgery
- Copyright © 2015 by the Society of Nuclear Medicine and Molecular Imaging, Inc.