Abstract
2095
Objectives Differentiated thyroid cancer (DTC) are claimed to express somatostatin receptor (sstr) subtypes 1,2,3 and 5. Commonly used radiolabeled oktreotid derivatives, i.e 111In-DTPA-Octreotide, 68Ga-DOTATOC target exclusively sstr subtype 2 (sstr2) and useful in imaging of iodine-negative DTC. However DOTA-NOC has been suggested to be the most promising peptide because of a broader SSTR subtype affinity including sstr2, sstr3 and sstr5 as compared to those of DOTATOC and DOTATATE. We aimed to compare diagnostic value of 68Ga-DOTA-NOC and 68Ga-DOTA-TATE (characterized by a very high affinity for sstr2) PET/CT in patients with iodine negative DTC.
Methods 13 patients (F/M: 8/7, median 63) with iodine negative differentiated thyroid cancer were prospectively examined. Patients were injected intravenously 125±25 / 122±29 MBq 68Ga-DOTA-TATE and 68Ga-DOTA-NOC at least in 24 hours intervals. 30-60 minutes after injection of radiolabelled peptides PET/CT images were obtained. Images were evaluated visually and SUVmax values of the lesions were calculated.
Results Results: In 5 patients (38%) no pathologic uptake was seen with both tracers. In 7 patients (62%) pathologic uptake was seen with both radiotracers. Uptakes of lesions were significantly higher with DOTA-TATE (TATE:12,9±9,1; NOC:6,2±4; p<0,005) . DOTA-TATE detected more lesions (TATE: 45 NOC: 42) however the difference was not significant. There were discordant results in two patients regarding SUVmax of lesions.
Conclusions Our study demonstrated that the images obtained by two tracers are comparable and have equally high quality. Sensitivities of both radiopeptide are equal however uptake of DOTA-NOC is lower presumably due to receptor distribution heterogeneity.
Research Support This work was supported by Scientific Research Projects Coordination Unit of Istanbul University. Project number 3264