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Abstract: We present a case of a 60-year-old woman diagnosed with metastasized small bowl NET G3 with high hepatic tumor burden and highly glucometabolic (FDG-avid) disease. In the postchemotherapy setting with progressive disease, the patient underwent PRRT with 177Lu-DOTA-octreotate and 225Ac-DOTA-octreotate initially resulting in stable disease. In a novel approach, 225Ac-DOTA-LM3 (somatostatin receptor antagonist) was administered, leading to a favorable treatment response in the 18F-FDG PET/CT scan. This interesting image illustrates the promising antitumor potential of alpha-sst2 antagonist PRRT with 225Ac-DOTA-LM3, and to the best of our knowledge, it is the first documented evidence of superiority over standard alpha-PRRT from intraindividual comparison., Competing Interests: Conflicts of interest and sources of funding: none declared., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

This study evaluated the impact of 68 Ga-DOTATOC PET/CT in detecting recurrence or metastases in differentiated thyroid carcinoma (DTC) patients with elevated serum thyroglobulin and both negative radioiodine imaging and negative 18 F-FDG PET/CT., Methods: 68 Ga-DOTATOC PET/CT (CT without contrast, low-dose) was performed on average 6 wk after negative 18 F-FDG PET/CT (CT contrast-enhanced, full-dose) in 15 consecutive radioiodine-negative DTC patients with elevated and rising thyroglobulin. Visual assessment of 68 Ga-DOTATOC PET/CT images used a 4-point scale for classification of lesions (0, no pathologic findings; 1, benign; 2, equivocal; 3, malignant). PET findings were correlated with the histologic subtype of tumor, levels of serum thyroglobulin, and morphologic findings on full-dose CT and neck ultrasound. Histology or clinical and imaging follow-up served as a reference standard. Analysis was performed on a patient and lesion basis., Results: 68 Ga-DOTATOC PET/CT was true-positive in 5 patients (10 tumor lesions) and was false-positive in 1 patient. The rate of positive 68 Ga-DOTATOC PET/CT was significantly higher in poorly differentiated/oxyphilic carcinomas (4/4 patients) than in papillary (1/5) or follicular (0/6) tumors. Thyroglobulin levels tended to be higher in patients with tumor localization on 68 Ga-DOTATOC PET/CT, but differences were not significant. In 2 of 5 patients with true-positive findings on 68 Ga-DOTATOC PET/CT, CT alone but not ultrasound identified 2 of 10 tumor lesions, but in both patients 68 Ga-DOTATOC-PET/CT revealed further tumor lesions not detected on CT alone., Conclusion: 68 Ga-DOTATOC PET/CT should be considered in the case of negative 18 F-FDG PET/CT in radioiodine-negative DTC patients with elevated and rising thyroglobulin. Imaging with 68 Ga-DOTATOC appears promising especially in poorly differentiated and oxyphilic subtypes of DTC., (© 2016 by the Society of Nuclear Medicine and Molecular Imaging, Inc.)

Peptide receptor radionuclide therapy (PRRT) with (90)Y-octreotide or (177)Lu-octreotate is an effective treatment for inoperable or metastatic neuroendocrine tumors (NETs), particularly well-differentiated gastroenteropancreatic or bronchopulmonary NETs. PRRT is generally extremely well tolerated, with modest toxicity to target organs, kidney and bone marrow. Nevertheless, a priori concerns regarding long-term effects lead clinicians such as Brieau and coworkers, in this ERC issue, to ascribe to the combination of alkylating agents and PRRT the apparently high occurrence (n=4) of myeloproliferative events (therapy-related myeloid neoplasms (t-MNs)) in a small cohort of 20 progressive, advanced digestive NETs treated with PRRT after chemotherapy. Anecdotal reports of myelotoxic events should be placed in the correct perspective of larger series, where the reported incidence of these events is ~2%, with the aim of promoting a balanced awareness of the issue and unbiased and reasonable overall conclusions. For a comprehensive definition of the issue, we provide an evaluation of the occurrence of t-MN in patients treated with various myelotoxic treatments., (© 2016 Society for Endocrinology.)

Background: Monocentric and retrospective studies indicate effectiveness of peptide receptor radionuclide therapy targeting somatostatin receptors of neuroendocrine neoplasms. We assessed overall and progression-free survival and adverse events of peptide receptor radionuclide therapy by a multi-institutional, board certified registry with prospective follow-up in five centres in Germany., Methods: A total of 450 patients were included and followed for a mean of 24.4 months. Most patients had progressive low- or intermediate grade neuroendocrine neoplasms and 73% were pretreated with at least one therapy. Primary neuroendocrine neoplasms were mainly derived of pancreas (38%), small bowel (30%), unknown primary (19%) or bronchial system (4%). Patients were treated with Lutetium-177 in 54%, with Yttrium-90 in 17% and with both radionuclides in 29%. Overall and progression-free survival was determined with Kaplan-Meier curves and uni-variate log rank test Cox models., Findings: Median overall survival of all patients was 59 (95% confidence interval [CI] 49-68.9) months. Overall survival was significantly inferior in the patients treated with Yttrium-90 solely (hazard ratio, 3.22; 95% CI, 1.83-5.64) compared to any peptide receptor radionuclide therapy with Lutetium-177. Grade II (hazard ratio, 2.06; 95% CI, 0.79-5.32) and grade III (hazard ratio, 4.22; 95% CI, 1.41-12.06) neuroendocrine neoplasms had significantly worse overall survival than grade I neuroendocrine neoplasms. Patients with small neuroendocrine neoplasms of small bowel had significantly increased survival (hazard ratio, 0.39; 95% CI, 0.18-0.87) compared to neuroendocrine neoplasms of other locations. Median progression-free survival was 41 (35.9-46.1) months and significantly inferior in patients treated with Yttrium solely (hazard ratio, 2.7; 95% CI, 1.71-4.55). Complete remission was observed in 5.6% of patients, 22.4% had a partial remission, 47.3% were stable and 4% were progressive as best response. Adverse events of bone marrow and kidney function higher than grade III occurred in 0.2-1.5% of patients., Interpretation: These results indicate that peptide receptor radionuclide therapy is a highly effective therapy for patients with low to intermediate grade neuroendocrine neoplasms with minor adverse events., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Purpose: Increasing evidence supports the value of peptide receptor radionuclide therapy (PRRT) in patients with metastatic neuroendocrine tumours (NET), but there are limited data on its specific efficacy in NET of small intestinal (midgut) origin. This study aims to define the benefit of PRRT with (177)Lu-octreotate for this circumscribed entity derived by a uniformly treated patient cohort., Methods: A total of 61 consecutive patients with unresectable, advanced small intestinal NET G1-2 stage IV treated with (177)Lu-octreotate (4 intended cycles at 3-month intervals, mean activity per cycle 7.9 GBq) were analysed. Sufficient tumour uptake on baseline receptor imaging and either documented tumour progression (n = 46) or uncontrolled symptoms (n = 15) were prerequisites for treatment. Response was evaluated according to modified Southwest Oncology Group (SWOG) criteria and additionally with Response Criteria in Solid Tumors (RECIST) 1.1. Assessment of survival was performed using Kaplan-Meier curves and Cox proportional hazards model for uni- and multivariate analyses. Toxicity was assessed according to standardized follow-up laboratory work-up including blood counts, liver and renal function, supplemented with serial (99m)Tc-diethylenetriaminepentaacetic acid (DTPA) clearance measurements., Results: The median follow-up period was 62 months. Reversible haematotoxicity (≥ grade 3) occurred in five patients (8.2%). No significant nephrotoxicity (≥ grade 3) was observed. Treatment response according to modified SWOG criteria consisted of partial response in 8 (13.1%), minor response in 19 (31.1%), stable disease in 29 (47.5%) and progressive disease in 5 (8.2%) patients. The disease control rate was 91.8%. Median progression-free survival (PFS) and overall survival (OS) was 33 [95% confidence interval (CI) 25-41] and 61 months (95% CI NA), respectively. Objective response was associated with longer survival (p = 0.005). Independent predictors of shorter PFS were functionality [hazard ratio (HR) 2.1, 95% CI 1.0-4.5, p = 0.05] and high plasma chromogranin A (CgA) levels > 600 ng/ml (HR 2.9, 95% CI 1.5-5.5, p < 0.001) at baseline., Conclusion: PRRT is well tolerated and very effective in advanced well-differentiated small intestinal (midgut) NET. A high disease control rate and long PFS can be achieved with this modality after failure of standard biotherapy with somatostatin analogues. Tumour functionality and high plasma CgA appear to be independent predictors of unfavourable patient outcome.

Purpose: The clinical benefit of peptide receptor radionuclide therapy (PRRT) in patients with pancreatic neuroendocrine tumours (pNET) has not yet been well described and defined in its full extent due to limited data in this tumour subgroup. This study was intended to obtain robust, comparative data on the outcome and toxicity of standardized PRRT with (177)Lu-octreotate in a well-characterized population of patients with advanced pNET of grade 1/2 (G1/2)., Methods: We retrospectively analysed a cohort of 68 pNET patients with inoperable metastatic disease consecutively treated with (177)Lu-octreotate (four intended cycles at 3-monthly intervals; mean activity per cycle 8.0 GBq). Of these 68 patients, 46 (67.6 %) had documented morphological tumour progression during the 12 months before initiation of treatment, and PRRT was the first-line systemic therapy in 35 patients (51.5 %). Response was evaluated according to modified Southwest Oncology Group (SWOG) criteria and additionally with Response Criteria in Solid Tumors (RECIST) 1.1. Survival was analysed using Kaplan-Meier curves and Cox proportional hazards model for univariate and multivariate analyses. Toxicity was assessed by standard follow-up laboratory work-up including blood count, and liver and renal function, supplemented with serial (99m)Tc-DTPA clearance measurements., Results: The median follow-up period was 58 months (range 4 - 112). Reversible haematotoxicity (grade 3 or more) occurred in four patients (5.9 %). No significant nephrotoxicity (grade 3 or more) was observed. Treatment responses (SWOG criteria) consisted of a partial response in 41 patients (60.3 %), a minor response in 8 (11.8 %), stable disease in 9 (13.2 %), and progressive disease in 10 (14.7 %). Median progression-free survival (PFS) and overall survival (OS) were 34 (95 % CI 26 - 42) and 53 months (95 % CI 46 - 60), respectively. A G1 proliferation status was associated with longer PFS (p = 0.04) and OS (p = 0.044) in the multivariate analysis. Variables linked to impaired OS, on the other hand, were a reduced performance status (Karnofsky score ≤ 70 %, p = 0.007), a high hepatic tumour burden (≥ 25 % liver volume, p = 0.017), and an elevated plasma level of neuron-specific enolase (NSE >15 ng/ml, p = 0.035)., Conclusion: The outstanding response rates and survival outcomes suggest that PRRT is highly effective in advanced G1/2 pNET when compared to data of other treatment modalities. Independent predictors of survival are the tumour proliferation index, the patient's performance status, tumour burden and baseline plasma NSE level.

Purpose: Renal radiation during peptide receptor radionuclide therapy (PRRT) may result in glomerular damage, a potential reduction of glomerular filtration rate (GFR) and ultimately lead to renal failure. While reported PRRT nephrotoxicity is limited to data derived from serum creatinine-allowing only approximate estimates of GFR-the aim of this study is to accurately determine PRRT-induced long-term changes of renal function and associated risk factors according to state-of-the-art GFR measurement., Methods: Nephrotoxicity was analysed using (99m)Tc-diethylenetriaminepentaacetic acid (DTPA) clearance data of 74 consecutive patients with gastroenteropancreatic neuroendocrine tumours (GEP NET) undergoing PRRT with (177)Lu-octreotate. The mean follow-up period was 21 months (range 12-50) with a median of five GFR measurements per patient. The change of GFR was analysed by linear curve fit. Potential risk factors including diabetes mellitus, arterial hypertension, previous chemotherapy, renal impairment at baseline and cumulative administered activity were analysed regarding potential impact on renal function loss. In addition, Common Terminology Criteria for Adverse Events (CTCAE) v3.0 were used to compare nephrotoxicity determined by (99m)Tc-DTPA clearance versus serum creatinine., Results: The alteration in GFR differed widely among the patients (mean -2.1 ± 13.1 ml/min/m(2) per year, relative yearly reduction -1.8 ± 18.9%). Fifteen patients (21%) experienced a mild (2-10 ml/min/m(2) per year) and 16 patients (22%) a significant (>10 ml/min/m(2) per year) decline of GFR following PRRT. However, 11 patients (15%) showed an increase of >10 ml/min/m(2) per year. Relevant nephrotoxicity according to CTCAE (grade ≥3) was observed in one patient (1.3%) with arterial hypertension and history of chemotherapy. Nephrotoxicity according to serum creatinine was discordant to that defined by GFR in 15% of the assessments and led to underestimation in 12% of patients. None of the investigated factors including cumulative administered activity contributed to the decline of renal function., Conclusion: Serious nephrotoxicity after PRRT with (177)Lu-octreotate is rare (1.3%). However, slight renal impairment (GFR loss >2 ml/min/m(2) per year) can frequently (43%) be detected by (99m)Tc-DTPA clearance assessments. Cumulative administered activity of (177)Lu-octreotate is not a major determinant of renal impairment in our study.

Purpose: We assessed the outcome and toxicity of salvage therapy (repeat treatment) with (177)Lu-octreotate and high cumulative activities in patients with metastatic gastroenteropancreatic neuroendocrine tumours (GEP-NET)., Methods: We retrospectively analysed a consecutive cohort of 33 patients with metastatic GEP-NET who underwent salvage peptide receptor radionuclide therapy (PRRT) in our institution. All patients had progressive NET prior to salvage treatment and had shown an initial response to PRRT. The mean cumulative activity was 44.3 GBq (30.0-83.7 GBq). Radiographic response was assessed using CT and/or MRI according to modified SWOG criteria. Toxicity was evaluated using laboratory data, including complete blood counts and renal function tests using CTCAE 3.0. Survival analysis was performed with the Kaplan-Meier curve method and a significance level at p < 0.05., Results: Radiographic responses consisted of complete response in 1 patient (3.0%), partial response in 6 patients (18.2%), minor response in 1 patient (3.0%), stable disease in 14 patients (42.4%), and progressive disease in 11 patients (33.3%). Median progression-free survival (PFS) from the start of salvage therapy was 13 months (95% CI 9-18) and patients with a history of a durable PFS after initial PRRT tended to have long-lasting PFS after salvage treatment (p = 0.04). None of the patients developed severe nephrotoxicity (grade 3/4) or a myelodysplastic syndrome during follow-up. Relevant albeit reversible haematotoxicity (grade 3/4) occurred in 7 patients (21.2%). The cumulative administered activity was not associated with an increased incidence of haematotoxicity., Conclusion: PRRT with (177)Lu-octreotate in the re-treatment setting is safe and effective in patients with metastatic GEP-NET.

Unlabelled: Outcome analyses for patients with gastroenteropancreatic neuroendocrine tumors (GEP NET) after peptide receptor radionuclide therapy (PRRT) are still limited, especially with regard to the impact of the Ki-67 index. Using a single-center analysis, we aimed to establish predictors of survival., Methods: We retrospectively analyzed a consecutive cohort of 74 patients who had metastatic GEP NET and underwent PRRT with (177)Lu-octreotate (mean activity of 7.9 GBq per cycle, aimed at 4 treatment cycles at standard intervals of 3 mo). Patients (33 with pancreatic NET and 41 with nonpancreatic GEP NET) had unresectable metastatic disease graded as G1 or G2 (G1/G2) and documented morphologic or clinical progression within less than 12 mo or uncontrolled disease under somatostatin analog treatment. Responses were evaluated according to modified Southwest Oncology Group criteria. Potential predictors of survival were analyzed with the Kaplan-Meier curve method (log-rank test) and multivariate analysis (P < 0.05)., Results: The response rates were 36.5% partial response, 17.6% minor response, 35.1% stable disease, and 10.8% progressive disease for the entire cohort; 54.5% partial response, 18.2% minor response, 18.2% stable disease, and 9.1% progressive disease for pancreatic NET; and 22.0% partial response, 17.1% minor response, 48.8% stable disease, and 12.2% progressive disease for nonpancreatic GEP NET. The median progression-free survival and overall survival were 26 mo (95% confidence interval, 18.3-33.7) and 55 mo (95% confidence interval, 48.8-61.2), respectively. Besides the Ki-67 index, a Karnofsky performance score of less than or equal to 70%, a hepatic tumor burden of greater than or equal to 25%, and a baseline plasma level of neuron-specific enolase of greater than 15 ng/mL independently predicted shorter overall survival (hazard ratio, 2.1-3.1). Patients with a Ki-67 index of greater than 10% still had median progression-free survival and overall survival of 19 and 34 mo, respectively., Conclusion: The results of this study demonstrated the favorable response and long-term outcome of patients with G1/G2 GEP NET after PRRT. Independent predictors of survival were the Ki-67 index, the patient's performance status (Karnofsky performance scale score), the tumor burden, and the baseline neuron-specific enolase level. Even patients with a Ki-67 index of greater than 10% seemed to benefit from PRRT, with a good response and a notable long-term outcome. We present the first evidence, to our knowledge, that even in patients with metastatic disease the distinction between G1 and G2-in particular, between G1 (Ki-67 index of 1%-2%) and low-range G2 (Ki-67 index of 3%-10%)-provides prognostic stratification.

Aim: Highly advanced metastatic bone disease with extensive osseous infiltration of neuroendocrine tumours (NET) may preclude patients from treatment with peptide receptor radionuclide therapy (PRRT) in concern about haematotoxicity. This study aims to assess the safety and efficacy of PRRT with 177Lu-octreotate in a patient cohort with this condition., Patients, Methods: 41 PRRT courses were performed in 11 patients with gastroenteropancreatic neuroendocrine tumours (GEP-NET) and florid bone metastases (severely advanced widespread metastatic bone disease). A mean activity of 6.95 GBq 177Lu-octreotate was administered per treatment cycle, aimed at four courses with standard intervals of 3 months. Haematological parameters were determined prior to each treatment course, in 2-4 weeks intervals between the courses, 8-12 weeks after the last course of PRRT and in 3 monthly intervals thereafter. Toxicity was recorded using Common Terminology Criteria for Adverse Events v3.0. Restaging was performed 3 months after termination of PRRT with CT/MRI and functional imaging (modified MDA criteria)., Results: Significant (grade III-IV), reversible haematotoxicity occurred in 4 (35%) patients and after 10 (24%) administrations. It either resolved spontaneously (1 patient) or was controlled by supportive measures (3 patients), such as blood transfusions (3 patients) or deferral of the subsequent therapy cycle (1 patient). Patients returned to baseline blood values within up to 23 months after termination of PRRT. The observed treatment response of bone metastases consisted of a partial response in 2, a minor response in 1, stable disease in 7, and progressive disease in 1 patient. Of the 4 patients with metastatic bone pain, 1 experienced complete and 3 partial resolution of symptoms within 3-10 weeks after commencement of PRRT., Conclusion: These preliminary data indicate that PRRT with 177Lu-octreotate can be safely applied even in florid bone metastases with extensive, severely advanced osseous replacement. The higher myelosuppression rate was not associated with serious complications and should not preclude patients from being treated and potentially experiencing remarkable treatment efficacy despite the very advanced stage.

Unlabelled: Myelosuppression may be the dose-limiting toxicity in peptide receptor radionuclide therapy (PRRT). The aim of this study was to investigate the incidence, severity, and reversibility of long-term hematotoxicity in a large cohort of patient undergoing PRRT with (177)Lu-octreotate for metastatic neuroendocrine tumors. The impact of potential risk factors, including initial cytopenia, advanced bone metastatic disease, previous chemotherapy, and cumulative administered activity, and the protective effects of splenectomy were of particular interest., Methods: A total of 632 PRRT courses were performed in 203 patients with metastatic neuroendocrine tumors. A mean activity of 7.9 GBq of (177)Lu-octreotate was administered per treatment cycle, with a goal of 4 courses at standard intervals of 3 mo. Hematologic parameters were determined before each treatment course, at 2- to 4-wk intervals between the courses, 8-12 wk after the last course of PRRT, and at 3-month intervals for further follow-up. Toxicity was recorded with Common Terminology Criteria for Adverse Events (version 3.0)., Results: Myelodysplastic syndrome as a delayed adverse event was documented in 3 patients (1.4%). Relevant but reversible hematotoxicity (grade 3 or 4) occurred in 23 patients (11.3%) and 29 administrations (4.6%), with leukopenia in 2.7% and thrombocytopenia in 1.7%. The mean time to blood count recovery was 12 mo after the termination of PRRT (range, 3-22 mo). The only preexisting factor that contributed to hematotoxicity was initial cytopenia (P < 0.001). A high level of cumulative administered activity (>29.6 GBq) was associated with relevant leukopenia (P < 0.001). None of the patients with a history of splenectomy developed grade 3 or 4 hematotoxicity, and splenectomy was inversely associated with the incidence and degree of leukopenia (P = 0.02) and thrombocytopenia (P = 0.03)., Conclusion: PRRT-induced myelosuppression is almost invariably reversible and rarely requires clinical measures. Administered activity and initial cytopenia are the only factors contributing to myelosuppression, whereas splenectomy may exert a protective effect.

Unlabelled: [177Lu-DOTA0,Tyr3]-octreotate (177Lu-octreotate) in peptide receptor radionuclide therapy (PRRT) offers direct intra-therapeutic dosimetry. The aim of this study was to compare tumour and non-tumour parameters and assess intra-individual variations., Patients, Methods: Retrospective analysis of 53 consecutive PRRT treatment cycles (mean activity of 7.53 ± 0.46 GBq 177Lu-octreotate, intended four cycles at intervals of 10-14 weeks, standard nephroprotection) in 27 GEP NET patients. Extended planar dosimetry with serial whole-body imaging on selected, non-superimposed tumour and non-tumour regions; liver (LM), bone (BM), and other (OM) metastases. The per-cycle variation was compared with post-treatment response (CT/MRI three months post-treatment, modified SWOG criteria)., Results: Residence time in tumor lesions (133-147 h) exceeded that in kidneys (93 h). Tumour-to-kidney absorbed dose ratios ranged from 14 to 28 (LM, BM, OM). Intra-individual per-cycle dose variation was insignificant for kidneys, but significant for metastases (LM, BM, and OM; p < 0.05). The mean per-cycle decrease of tumour absorbed dose (ΔD/A0[%]) was linked to morphologic response after PRRT. A mean decrease of >20% was predictive of a partial or minor remission in all 11 evaluable patients, while absent significant dose reduction indicated stable or progressive disease in 4/5 patients. The dose decrease was unrelated to volume effects and also observed for BM., Conclusion: Besides confirmation of a favourable tumour-to-kidney parameter relation for 177Lu-octreotate, stepwise intra-lesional comparison seems to imply a prognostic impact of tumor dosimetry: The early per-cycle change ΔD/A0 between treatment cycles may predict the outcome after PRRT. Larger studies are needed to confirm this finding.

Purpose: Selection of candidates for peptide receptor radionuclide therapy (PRRT) is increasingly based on receptor positron emission tomography (PET) imaging, including the common tracer 68Ga DOTATOC. However, no studies have yet compared standardized uptake values (SUVs) and absorbed doses in this field., Materials and Methods: We retrospectively analyzed a consecutive cohort of 21 patients with 61 evaluable tumor lesions undergoing both pretherapeutic 68Ga DOTATOC-PET/CT (Biograph Duo [Siemens Medical Solutions, Erlangen, Germany]; PET acquisition, 75.3 ± 15.4 minutes postinjection; 117.3 ± 33.9 MBq 68Ga DOTATOC) and PRRT with Lu octreotate (7.47 ± 1.39 GBq; intratherapeutic tumor dosimetry with serial whole-body scans; 1, 2, and 4 days postinjection) at our institution. SUVs were compared with the tumor-absorbed doses per injected activity (D/A0) of the subsequent first treatment cycle., Results: The correlation of SUV and D/A0 was r = 0.72 (SUVmean) and r = 0.71 (SUVmax), both P < 0.001. Pancreatic origin and hepatic localization were associated with higher D/A0, and chromogranin A level and Ki-67 index had no influence on SUV or D/A0. High-SUV lesions (SUVmean >15; SUVmax >25) resulted in high D/A0 (>10 Gy/GBq) in 66.7% to 70.8% and low D/A0 (<5 Gy/GBq) in only 8.3% to 12.5% on subsequent PRRT. The mentioned low D/A0 range, on the other hand, was achieved by all lesions with SUVmean <7 or SUVmax <9., Conclusions: Somatostatin receptor PET imaging may predict tumor-absorbed doses. The ability to indicate insufficient target irradiation by a low SUV could aid in selection of appropriate candidates for PRRT. However, larger series are needed to confirm and validate these initial findings.

Aim: Peptide receptor radionuclide therapy with 177Lu-octreotate is an effective treatment option for metastatic gastroenteropancreatic neuroendocrine tumors (GEP NET) and allows intratherapeutic imaging through a 177Lu-octreotate scan (LuS). The diagnostic value of this treatment scan is not yet established. This study aims to compare the sensitivity of LuS and bone scintigraphy (BS) regarding bone metastases and investigate potential implications of functional imaging results., Patients, Methods: We retrospectively analyzed 29 consecutive GEP NET patients with bone metastases and baseline BS treated with 177Lu-octreotate. A semi-quantitative scoring system was used for the comparative evaluation. Treatment outcome (time-to-progression of bone metastases) was correlated with the intra-individual imaging discrepancy (Kaplan-Meyer curves, log-rank test, p < 0.05)., Results: In 19 of 29 patients (65.5%) LuS was superior (LuS > BS), whereas in 10 patients (34.5%) both modalities were comparable. BS showed no additional (LuS-negative) metastatic bone lesions in our cohort. None of the investigated baseline characteristics was associated with imaging discrepancy. On the other hand, functional imaging discrepancy had no impact on treatment response (p = 0.43) or time-to-progression (p = 0.92)., Conclusions: Intra-therapeutic 177Lu-octreotate imaging is superior over bone scintigraphy for detection of bone metastases in GEP NET. BS may help to distinguish osseous from non-osseous localization. The presence of an osteoblastic correlate in BS seems to have no impact on therapeutic outcome.

Unlabelled: Peptide receptor radionuclide therapy (PRRT) is an efficient treatment for gastroenteropancreatic neuroendocrine tumors (GEP NETs), with outstanding overall response rates and survival. However, little is known about the particular efficacy regarding bone metastasis (BM)., Methods: We retrospectively analyzed a consecutive subgroup of 42 patients with BM of GEP NETs treated with PRRT ((177)Lu-octreotate, 4 intended cycles at 3 monthly intervals [10-14 wk]; mean activity per cycle, 8.1 GBq). Availability of restaging and outcome data was required for patient inclusion. Baseline characteristics, including age, tumor origin, performance score, Ki-67 index, tumor load, tumor uptake, plasma chromogranin A, and neuron-specific enolase, were analyzed regarding impact on tumor regression (modified M.D. Anderson criteria) and time to progression. Survival analyses were performed using Kaplan-Meier curves, log-rank test at a significance level of P less than 0.05, and Cox proportional hazards model for uni- and multivariate analyses., Results: Median follow-up was 32 mo. The observed response of BMs consisted of complete remission in 2 (4.8%), partial remission in 14 (33.3%), minor response in 5 (11.9%), stable disease in 16 (38.1%), and progressive disease in 5 (11.9%) patients. Median progression-free survival and overall survival (OS) were 35 mo (26-44, 95% confidence interval) and 51 mo (37-65, 95% confidence interval), respectively. Patients with responding BMs (complete remission, partial remission, or minor response) exhibited a trend toward better OS (median OS not reached after 53 mo) when compared to nonresponding patients (39 mo, P = 0.076). Only Ki-67 index (>10%) and chromogranin A level (>600 ng/mL) contributed to regression analysis., Conclusion: BM of GEP NETs is effectively controlled by PRRT, with long progression-free survival and OS. Poor patient condition and multifocality of BMs do not clearly affect treatment efficacy, possibly encouraging the use of PRRT in advanced bone metastatic disease. Larger studies are needed to assess predictors of treatment outcome in these patients.

Purpose: The medical treatment of metastatic medullary thyroid carcinoma (MTC) is still questionable. The aim of this study was to evaluate a combined imaging protocol using 111In-DTPA-octreotide and 131I/123I-MIBG to decide whether targeted radiotherapy would be useful, and which radiopharmaceutical (90Y-DOTATOC or 131I-MIBG) would be more effective., Methods: Eight patients (four men, four women; mean age 61 years) with metastatic MTC were included. Treatments were performed with 3,330 MBq 90Y-DOTATOC at 6-week intervals, or 11.1 GBq 131I-MIBG with a minimum interval of 3 months., Results: The imaging procedure was positive in all eight patients: 111In-DTPA-octreotide imaging in five patients, 131I/123I-MIBG imaging in four patients. With respect to the number of metastatic lesions, MIBG imaging was less effective than octreotide. According to the results of combined imaging, we identified one patient to be treated with 90Y-DOTATOC, and three patients with 131I-MIBG. An overall antitumor effect was observed in all four patients, one with partial remission and three with stable disease. No relevant toxicity was observed., Conclusions: The combined imaging can increase the detection rate of metastatic foci in patients with MTC and identify more patients for effective radionuclide treatment. The treatment with 90Y-DOTATOC or 131I-MIBG is well tolerated and may improve the fate of patients with metastatic MTC.