A comparison of simplified protocols of personalized dosimetry in NEN patients treated by radioligand therapy (RLT) with [177Lu]Lu-DOTATATE to favor its use in clinical practice.

The role of internal dosimetry is usually proposed for investigational purposes in patients treated by RLT, even if its application is not yet the standard method in clinical practice. This limited use is partially justified by several concomitant factors that make calculations a complex process. Therefore, simplified dosimetry protocols are required. METHODS: In our study, dosimetric evaluations were performed in thirty patients with NENs who underwent RLT with [177Lu]Lu-DOTATATE. The reference method (M0) calculated the cumulative absorbed dose performing dosimetry after each of the four cycles. Obtained data were employed to assess the feasibility of simplified protocols: defining the dosimetry only after the first cycle (M1) and after the first and last one (M2). RESULTS: The mean differences of the cumulative absorbed doses between M1 and M0 were - 10% for kidney, - 5% for spleen, + 34% for liver, + 13% for red marrow, and + 37% for tumor lesions. Conversely, differences lower than ± 10% were measured between M2 and M0. CONCLUSION: Cumulative absorbed doses obtained with the M2 protocol resembled the doses calculated by M0, while the M1 protocol overestimated the absorbed doses in all organs at risk, except for the spleen.

Analysis of Pros and Cons in Using [68Ga]Ga-PSMA-11 and [18F]PSMA-1007: Production, Costs, and PET/CT Applications in Patients with Prostate Cancer.

The aim of this work is to compare [68Ga]Ga-PSMA-11 and [18F]PSMA-1007 PET/CT as imaging agents in patients with prostate cancer (PCa). Comparisons were made by evaluating times and costs of the radiolabeling process, imaging features including pharmacokinetics, and impact on patient management. The analysis of advantages and drawbacks of both radioligands might help to make a better choice based on firm data. For [68Ga]Ga-PSMA-11, the radiochemical yield (RCY) using a low starting activity (L, average activity of 596.55 ± 37.97 MBq) was of 80.98 ± 0.05%, while using a high one (H, average activity of 1436.27 ± 68.68 MBq), the RCY was 71.48 ± 0.04%. Thus, increased starting activities of [68Ga]-chloride negatively influenced the RCY. A similar scenario occurred for [18F]PSMA-1007. The rate of detection of PCa lesions by Positron Emission Tomography/Computed Tomography (PET/CT) was similar for both radioligands, while their distribution in normal organs significantly differed. Furthermore, similar patterns of biodistribution were found among [18F]PSMA-1007, [68Ga]Ga-PSMA-11, and [177Lu]Lu-PSMA-617, the most used agent for RLT. Moreover, the analysis of economical aspects for each single batch of production corrected for the number of allowed PET/CT examinations suggested major advantages of [18F]PSMA-1007 compared with [68Ga]Ga-PSMA-11. Data from this study should support the proper choice in the selection of the PSMA PET radioligand to use on the basis of the cases to study.

On site production of [18F]PSMA-1007 using different [18F]fluoride activities: practical, technical and economical impact.

BACKGROUND: Prostate-specific membrane antigen is overexpressed in prostate cancer and it is considered a good target for positron emission tomography/computed tomography imaging of primary cancer and recurrent/metastatic disease, as well as for radioligand therapy. Different PSMA-analogues labeled with [68Ga]gallium have been investigated, showing excellent imaging properties; however, only small amounts can be produced for each radiolabeling. Recently, a [18F]fluoride labeled PSMA-inhibitor, [18F]PSMA-1007, has been introduced, and it has ensured large-scale productions, overcoming this limitation of [68Ga]PSMAs. In this study, PSMA-1007 has been labeled with low (A), medium (B) and high (C) starting activities of [18F]fluoride, in order to verify if radiochemical yield, radiochemical purity and stability of [18F]PSMA-1007 were affected. These parameters have been measured in sixty-five consecutive batches. In addition, the estimation of [18F]PSMA-1007 production costs is provided. RESULTS: The radiochemical yield for low and medium activities of [18F]fluoride was 52%, while for the high one it decreased to 40%. The radiochemical purity was 99% for all three activities. [18F]PSMA-1007 did not show radiolysis up to 8 h after the end of synthesis, confirming that the radiopharmaceutical is stable and suitable to perform diagnostic studies in humans for a long period of time after the end of radiolabeling. Furthermore, radiochemical stability was demonstrated in fetal bovine serum at 4 °C and 37 °C for 120'. CONCLUSIONS: A starting activity of [18F]fluoride of 90 GBq (B) seems to be the best option enabling a final amount of about of 50 GBq of [18F]PSMA-1007, which is promising as it allows to: (a) perform a large number of scans, and/or (b) supply the radiopharmaceutical to any peripheral diagnostic centers in need.

Role of (68)Ga-DOTATATE PET/CT in patients with multiple endocrine neoplasia type 1 (MEN1).

Multiple endocrine neoplasia type 1 (MEN1) is a hereditary syndrome predisposing to many endocrine and neuroendocrine tumors (NET). Conventional imaging (CI) cannot provide satisfactory results for all the different types of MEN1-related tumors. Objective of this prospective observational study was to evaluate the role of (68)Ga-DOTATATE PET/CT in MEN1 compared to CI. Diagnostic performance of (68)Ga-DOTATATE PET/CT for the detection of NET was evaluated as well as the prognostic role of SUVmax. Eighteen patients with genetically confirmed MEN1 were evaluated by (68)Ga-DOTATATE PET/CT, endoscopic ultrasounds, multidetector-row computed tomography, magnetic resonance imaging, and hormone/markers serum measurements. Four MEN1-related tumor sites (pancreas, pituitary, parathyroids, adrenals) were considered. Sensitivity and specificity of (68)Ga-DOTATATE PET/CT for the detection of NET were calculated. There was (68)Ga-DOTATATE PET/CT uptake in 11/11 patients with pancreatic lesions, in 9/12 with pituitary adenoma, in 5/15 with parathyroid enlargements, and in 5/7 with adrenal lesions. (68)Ga-DOTATATE PET/CT showed sensitivity and specificity of 100 and 100 % in pancreas, 75 and 83 % in pituitary, 28 and 100 % in parathyroids, and 62.5 and 100 % in adrenals, respectively. Compared with CI, no significant difference in sensitivity for pancreas, pituitary, and adrenals was found, while CI had a better sensitivity for parathyroids (p = 0.002). On the ROC analysis, progression of pancreatic lesions was significantly associated to SUVmax <12.3 (p < 0.05). (68)Ga-DOTATATE PET/CT is greatly helpful in the work-up of MEN1 providing a panoramic view of MEN1-related lesions. There is also a prognostic role of (68)Ga-PET in patients with MEN1-pancreatic lesions.

Radioimmunotherapy with Tenarad, a 131I-labelled antibody fragment targeting the extra-domain A1 of tenascin-C, in patients with refractory Hodgkin's lymphoma.

PURPOSE: The extra-domain A1 of tenascin-C (TC-A1) is highly expressed in the extracellular matrix of tumours and on newly formed blood vessels and is thus a valuable target for radionuclide therapy. Tenarad is a fully human miniantibody or small immunoprotein (SIP, molecular weight 80 kDa) labelled with (131)I that is derived from a TC-A1-binding antibody. Previous phase I/II studies with a similar compound ((131)I-L19SIP) used for radioimmunotherapy (RIT) have shown preliminary efficacy in a variety of cancer types. In this ongoing phase I/II trial, Tenarad was administered to patients with recurrent Hodgkin's lymphoma (HL) refractory to conventional treatments. METHODS: Eight patients (four men, four women; age range 19 - 41) were enrolled between April 2010 and March 2011. All patients had received a median of three previous lines of chemotherapy (range three to six) and seven had also undergone autologous stem cell transplantation (ASCT) or bone marrow transplantation. In addition, seven patients received external beam radiation. All patients had nodal disease, constitutional B symptoms and some showed extranodal disease in skeletal bone (four patients), lung (three), liver (two) and spleen (one). Baseline assessments included whole-body FDG PET with contrast-enhanced CT and diagnostic Tenarad planar and SPECT studies. Patients were considered eligible to receive a therapeutic dose of Tenarad (2.05 GBq/m(2)) if tumour uptake was more than four times higher than that of muscle. RESULTS: All patients were eligible and received the therapeutic dose of Tenarad. Only one patient developed grade 4 thrombocytopenia and leucocytopenia, requiring hospitalization and therapeutic intervention. All other patients had haematological toxicity of grade 3 or lower, which resolved spontaneously. At the first response assessment (4 - 6 weeks after therapy), one patient showed a complete response, one showed a partial response (PR) and five had disease stabilization (SD). Five patients were given up to three repeated Tenarad treatments. One patient showed SD which then improved to a PR, three showed clinical benefit while maintaining SD and one patient showed disease progression. CONCLUSION: Tenarad RIT is effective in chemorefractory HL and resulted in objective responses or clinical benefit in the majority of patients. Toxicity was acceptable despite the high load of prior treatments, previous ASCT and multiple Tenarad administrations. Further studies are planned to define the most effective schedule for this type of RIT in HL patients.

Twenty years of radiobiology in clinical practice: the Italian contribution.

AIMS AND BACKGROUND: To present the Italian state-of-the-art contribution to radiobiology of external beam radiotherapy, brachytherapy, and radionuclide radiotherapy. METHODS AND STUDY DESIGN: A survey of the literature was carried out, using PubMed, by some independent researchers of the Italian group of radiobiology. Each paper was reviewed by researchers of centers not comprising its authors. The survey was limited to papers in English published over the last 20 years, written by Italian investigators or in Italian institutions, excluding review articles. RESULTS: A total of 135 papers have been published in journals with an impact factor, with an increase in the number of published papers over time, for external beam radiotherapy rather than radionuclide radiotherapy. The quantity and quality of the papers researched constitutes a proof of the enduring interest in clinical radiobiology among Italian investigators. CONCLUSIONS: The survey could be useful to individuate expert partners for an Italian network on clinical radiobiology, addressing future collaborative investigations.

Comparison of the binding and internalization properties of 12 DOTA-coupled and ¹¹¹In-labelled CCK2/gastrin receptor binding peptides: a collaborative project under COST Action BM0607.

PURPOSE: Specific overexpression of cholecystokinin 2 (CCK2)/gastrin receptors has been demonstrated in several tumours of neuroendocrine origin. In some of these cancer types, such as medullary thyroid cancer (MTC), a sensitive diagnostic modality is still unavailable and therapeutic options for inoperable lesions are needed. Peptide receptor radionuclide therapy (PRRT) may be a viable therapeutic strategy in the management of these patients. Several CCK2R-targeted radiopharmaceuticals have been described in recent years. As part of the European Union COST Action BM0607 we studied the in vitro and in vivo characteristics of 12 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-conjugated CCK2R binding peptides. In the present study, we analysed binding and internalization characteristics. Stability, biodistribution and imaging studies have been performed in parallel by other centres involved in the project. METHODS: Determination of IC(50) values was performed using autoradiography, with DOTA-peptides displacing (125)I-CCK from receptors on tissue sections from human tumours. Saturation binding and internalization experiments were performed using (111)In-labelled peptides. The rat AR42J cell line and the human A431-CCK2R transfected cell line were utilized for in vitro experiments; dissociation constants (K(d)) and apparent number of binding sites (B(max)) were determined. Internalization was determined in receptor-expressing cells by incubating with tracer amounts of peptide at 37 and 4°C for different times up to 120 min. Surface-bound peptide was then stripped either by acid wash or subsequent incubation with 1 µM unlabelled peptide at 4°C. RESULTS: All peptides showed high receptor affinity with IC(50) values ranging from 0.2 to 3.4 nM. Saturation experiments also showed high affinity with K(d) values in the 10(-9)-10(-8) M range. B(max) values estimated in A431-CCK2R cells ranged from 0.6 to 2.2 × 10(6) per cell. All peptides showed high levels of internalization when incubated at 37°C. CONCLUSION: All DOTA-conjugated peptides showed high receptor binding and internalization properties and appear suitable for further characterization, as described in other articles of this issue.