Cu-64-TETA-Octreotide as a PET imaging agent for patients with neuroendocrine tumors

(CU)-C-64 (half-life, 12.7 h; beta+, 0.653 MeV [17.4%]; beta (-), 0.579 MeV [39%]) has shown potential as a radioisotope for PET imaging and radiother apy. In-111-diethylenetriaminepentaacetic acid (DTPA)-D-Phe(1)-octreotide ( OC) was developed for imaging somatostatin-receptor-positive tumors using c onventional scintigraphy. With the advantages of PET over conventional scin tigraphy, an agent for PET imaging of these tumors is desirable. Here, we s how that Cu-64-TETA-OC (where TETA is 1,4,8,11-tetraazacyclotetradecane-N,N ',N " ,N''' -tetraacetic acid) and PET can be used to detect somatostatin-r eceptor-positive tumors in humans. Methods: Eight patients with a history o f neuroendocrine tumors (five patients with carcinoid tumors and three pati ents with islet cell tumors) were imaged by conventional scintigraphy with In-111-DTPA-OC (204-233 MBq [5.5-6.3 mCi]) and by PET imaging with Cu-64-TE TA-OC (111 MBq [3 mCi]). Blood and urine samples were collected for pharmac okinetic analysis. PET images were collected at times ranging from 0 to 36 h after injection, and the absorbed doses to normal organs were determined. Results: In six of the eight patients, cancerous lesions were visible by b oth In-111-DTPA-OC SPECT and Cu-64-TETA-OC PET. In one patient, In-111-DTPA -OC showed mild uptake in a lung lesion that was not detected by (CU)-C-64- TETA-OC PET. In one patient, no tumors were detected by either agent; howev er, pathologic follow-up indicated that the patient had no tumors. In two p atients whose tumors were visualized with In-111-DTPA-OC and Cu-64-TETA-OC, (CU)-C-64-TETA-OC and PET showed more lesions than In-111-DTPA-OC. Pharmac okinetic studies showed that Cu-64-TETA-OC was rapidly cleared from the blo od and that 59.2% +/- 17.6% of the injected dose was excreted in the urine. Absorbed dose measurements indicated that the bladder wall was the dose-li miting organ. Conclusion: The high rate of lesion detection, sensitivity, a nd favorable dosimetry and pharmacokinetics of Cu-64-TETA-OC indicate that it is a promising radiopharmaceutical for PET imaging of patients with neur oendocrine tumors.