Utility of [99m]Tc-PEG[4]-E[PEG[4]-c[RGDFK]][2] in posttherapy surveillance of patients with reelevated carcinoembryonic antigen levels

ABSTRACT

To evaluate the efficacy of [99m]Tc-PEG[4]-E[PEG[4]-c [RGDfK]][2][[99m]Tc-3PRGD2] single photon emission computed tomography [SPECT] in monitoring the recurrence of malignancies. Materials and [99m]Tc-3PRGD2 SPECT was performed on 28 patients [10 females and 18 males; median age 49.2 years] suspected of recurrent malignancies due to an asymptomatically reelevated carcinoembryonic antigen level. The SPECT was performed 0.5 h after an intravenous injection of 11.1 MBq/kg [0.3 mCi/kg] of [99m]Tc-3PRGD2. The SPECT and concurrent contrast-enhanced computed tomography [ceCT] findings were analyzed with reference to the histopathological findings and/or clinical follow-up data. Recurrences were identified in 20 out of the 28 patients [prevalence 71.4%] with altogether 26 lesions. Fifteen lesions were confirmed by histopathological findings, and the other 11 lesions were confirmed by serial radiological or clinical follow-up. Of the 20 patients with recurrent malignancies, 12 [60%] were correctly identified by [99m]Tc-3PRGD2 SPECT. In the patient-based analysis, the sensitivity and specificity of [99m]Tc-3PRGD2 SPECT were 60 and 100%, respectively, and the positive and negative predictive values were 100 and 50%, respectively. In the lesion-based evaluation, the sensitivity and specificity were 62 and 100%, respectively. The sensitivity and specificity of the ceCT in the patient-based evaluation were 60 and 75%, respectively, and the positive and negative predictive values were 86 and 40%, respectively. In the lesion-based evaluation, the sensitivity and specificity of the ceCT were 70 and 84%, respectively. [99m]Tc-3PRGD2, as a new SPECT tracer targeting the integrin alpha[v]beta[3] receptor, was more useful in distinguishing recurrences as compared to ceCT