Identification of the Optimal Cut-Off Value of PSA for Assessing Severity of Disease in [68Ga]Ga-PSMA-11 PET/CT Study in Prostate Cancer Patients after Radical Prostatectomy.

OBJECTIVE: The objective of this study was to identify the optimal cut-off value of prostate specific antigen (PSA) to assess the extent of the disease in [68Ga]Ga-PSMA-11 PET/CT study in patients after radical prostatectomy. MATERIALS AND METHODS: Retrospective analysis was performed on a group of 215 patients who underwent a [68Ga]Ga-PSMA-11 PET/CT examination because of suspected recurrence after radical prostatectomy. Patients were divided into four groups: 1, no active lesions suggesting recurrence (n = 92); 2, suspected isolated local recurrence (n = 19); 3, oligometastatic disease (n = 82); and 4, polymetastatic disease (n = 22). RESULTS: In group 1, the mean PSA level was 0.962 ng/mL (median: 0.376; min: 0.004; max: 25 ng/mL); in group 2, it was 4.970 ng/mL (median 1.320; min: 0.003; max: 40.350 ng/mL); in group 3, it was 2.802 ng/mL (median: 1.270; min: 0.020; max: 59.670 ng/mL); and in group 4, it was 4.997 ng/mL (median: 3.795; min: 0.007; max 21.110 ng/mL). Statistically significant differences were shown in PSA levels when comparing groups 1 and 2 (p = 0.0025) and groups 3 and 4 (p = 0.0474). The PSA cut-off point for discriminating groups 1 and 2 was 0.831 (sensitivity: 0.684; specificity: 0.772; area under the curve (AUC): 0.775), and for groups 3 and 4, it was 2.51 (sensitivity: 0.682; specificity: 0.780; AUC: 0.720). CONCLUSIONS: Our preliminary data suggested that the PSA level has an essential influence on determining the extent of disease in a [68Ga]Ga-PSMA-11 PET/CT study in patients after radical prostatectomy. Identification of the optimal cut-off values for the oligo- and polymetastatic diseases might be helpful in stratifying these patients.

99mTc-labeled vasopressin peptide as a radiopharmaceutical for small-cell lung cancer (SCLC) diagnosis.

The 99mTc-labeled conjugates of the vasopressin (AVP) peptide and of its analogue d(CH2)5[D-Tyr(Et2)-Ile4-Eda9]AVP (AVP(an)) have been synthesized using the technetium complexes with tetradentate tripodal chelator (the tris(2-mercaptoethyl)amine (NS3)) and the monodentate isocyanide ligand (CN-peptide). The conjugates exhibit high stability in the presence of 100 times the molar excess of standard amino acids cysteine or histidine and also satisfactory stability in human serum. The 99mTc(NS3)(CN-AVP) and 99mTc(NS3)(CN-AVP(an)) ability of binding to small-cell lung cancer (SCLC) cell line H69 was studied in vitro. The results suggest that the novel vasopressin conjugate 99mTc(NS3)(CN-AVP(an)) is a desirable compound for imaging oncogene receptors overexpressed in SCLC cells and can be an important basis for further consideration the conjugate as a potential diagnostic radiopharmaceutical for patients suffering from small-cell lung cancer.

The diagnostic role of 68Ga-DOTATATE PET/CT in the detection of neuroendocrine tumours.

BACKGROUND: Positron emission tomography (PET) combined with computer tomography (CT) using (68)Ga-DOTATATE is a promising method for the evaluation of patients with recognised or suspected neuroendocrine tumours (NET). The aim of this study was to assess the diagnostic value of (68)Ga-DOTATATE PET/CT in the visualisation of the expression of somatostatin receptors (SSTR) and identification of new lesions. MATERIAL AND METHODS: Between December 2009 and January 2011 ninety-seven patients with confirmed (88 cases) or suspected (9 cases) NET underwent (68)Ga DOTATATE PET/CT. The primary, confirmed or suspected, NET localizations were: GEP tumours--71 patients; medullary thyroid carcinoma--4 patients; cancer of an unknown primary--14 patients; and NET in other localisations--8 patients. PET/CT acquisitions were performed using standard techniques, 45 to 60 minutes after the intravenous injection of 111-185 MBq (68)Ga-DOTATATE. RESULTS: (68)Ga-DOTATATE PET/CT detected the presence of lesions demonstrating the somatostatin receptor affinity in 50 of the 97 patients (51.5%) and was negative in 47 patients (48.5%). Among 14 patients with metastatic unknown primary cancer, in 5 patients (45.5%) the primary tumour site was identified, and in 4 patients with medullary thyroid cancer distant metastases with SSTR expression were localized in only one patient. CONCLUSIONS: Our findings confirm the diagnostic role of (68)Ga-DOTATATE PET/CT as an accurate method of identifying primary tumours and distant metastases. It provides information on tumour cell receptors status, which has a significant bearing on planning target radionuclide therapy. Overall, (68)Ga-DOTATATE PET/CT can be used in staging, re-staging, and in regular follow up of oncology patients.