Radioligand therapy (RLT) as neoadjuvant treatment for inoperable pancreatic neuroendocrine tumors: a literature review

Epidemiology of Neuroendocrine Neoplasms and Results of Their Treatment with [177Lu]Lu-DOTA-TATE or [177Lu]Lu-DOTA-TATE and [90Y]Y-DOTA-TATE-A Six-Year Experience in High-Reference Polish Neuroendocrine Neoplasm Center

Neuroendocrine neoplasms (NENs) are a group of neoplasms arising from neuroendocrine cells. The worldwide incidence and prevalence of the NENs are estimated to be 6/100,000 and 35/100,000, respectively. Those numbers are increasing every decade, requiring higher and higher diagnosis and treatment costs. Radioligand therapy (RLT) using beta-emitting radioisotopes is an efficient and relatively safe method of treatment, typically used as a second-line treatment. RLT tolerability is higher than other available pharmacotherapies (chemotherapy or tyrosine kinase inhibitors). Recent studies show an increase in overall survival among patients treated with RLT. The present study aimed to learn the epidemiology of NENs in Poland and assess the effectiveness of RLT in a high-reference center. A prospective analysis of 167 patients treated with RLT in one of Poland's highest-reference NEN centers was performed. The analysis covered 66 months of observation (1 December 2017-30 May 2023), during which 479 RLT single administrations of radioisotope were given. The standard procedure was to give four courses of [177Lu]Lu-DOTA-TATE alone, or tandem therapy-[177Lu]Lu-DOTA-TATE and [90Y]Y-DOTA-TATE. Grading analysis showed that most patients had non-functioning G2 NEN with a mean Ki-67 of 6.05% (SD ± 6.41). The most common primary tumor location was the pancreas. Over two-thirds of patients did undergo surgery due to primary tumors or distant metastases. The majority of patients were using lanreotide as a chronically injected somatostatin analog. Median progression-free survival (PFS) on somatostatin analogs was 21.0 (IQR = 29.0) months. Directly after the last course of RLT, disease stabilization was noted in 69.46% of patients, partial regression was noted in 20.36% of patients, complete regression was noted in 0.60% of patients, and progression was noted in 9.58% of patients. In long-term follow-up, the median observation time among patients who underwent four treatment cycles (n = 108) was 29.8 (IQR = 23.9) months. Stabilization of the disease was observed in 55.56% of the patients and progression was observed in 26.85% of the patients, while 17.59% of patients died. Median PFS was 29.3 (IQR 23.9), and the median OS was 34.0 months (IQR 16.0). The mean age of NEN diagnosis is the sixth decade of life. It takes almost three years from NEN diagnosis to the start of RLT. In long-term observation, RLT leads to disease stabilization in over half of the patients with progressive disease. No differences in PFS or OS depend on the radioisotope used for RLT. In Poland, organized coordination of NEN treatment in high-reference centers ensures the continuity of patient care.

Hepato-Biliary Imaging in an Acute Setting: Is There a Role for Nuclear Medicine?

Nuclear medicine (NM) is not commonly considered as a first-line imaging modality in hepato-biliary (HB) emergencies. The aim of this review is to provide an update on the potential of NM for the imaging of HB emergencies. 99mTc-HIDA scintigraphy showed high diagnostic accuracy for acute cholecystitis, thus being particularly useful in patients at high-risk for surgery due to comorbidities and with no clear findings at US or CT. Although limitedly explored, White blood cell (WBC) scan might have a role in case of acute pancreatitis, especially for the imaging of pancreatic leukocyte infiltration and the prediction of pancreatic necrosis. Scientific literature on 18F-FDG-PET/CT in HB acute disease mainly consists of case reports or case series, describing incidental findings in oncological PET/CT scans. In patients with obstructive jaundice, PET/CT has been proposed to disclose and characterize occult tumoral etiology. Further studies are needed to evaluate the clinical usefulness of the various NM approaches in HB acute settings, particularly with respect to the emerging new technologies (eg, PET/MRI) and radiopharmaceuticals.

Lutathera® Orphans: State of the Art and Future Application of Radioligand Therapy with 177Lu-DOTATATE

Lutathera® is the first EMA- and FDA-approved radiopharmaceutical for radioligand therapy (RLT). Currently, on the legacy of the NETTER1 trial, only adult patients with progressive unresectable somatostatin receptor (SSTR) positive gastroenteropancreatic (GEP) neuroendocrine neoplasms (NET) can be treated with Lutathera®. Conversely, patients with SSTR-positive disease arising from outside the gastroenteric region do not currently have access to Lutathera® treatment despite several papers in the literature reporting the effectiveness and safety of RLT in these settings. Moreover, patients with well-differentiated G3 GEP-NET are also still “Lutathera orphans”, and retreatment with RLT in patients with disease relapse is currently not approved. The aim of this critical review is to summarize current literature evidence assessing the role of Lutathera® outside the approved indications. Moreover, ongoing clinical trials evaluating new possible applications of Lutathera® will be considered and discussed to provide an updated picture of future investigations.

Relevance of Volumetric Parameters Applied to [68Ga]Ga-DOTATOC PET/CT in NET Patients Treated with PRRT

BACKGROUND

this study aims to explore the prognostic and predictive role of volumetric parameters on [⁶⁸Ga]Ga-DOTATOC PET/CT in neuroendocrine tumors (NET) patients treated with peptide receptor radionuclide therapy (PRRT).

METHODS

We retrospectively evaluated 39 NET patients (21 male, 18 female; mean age 60.7 y) within the FENET-2016 trial (CTiD:NCT04790708). PRRT was proposed with [¹⁷⁷Lu]Lu-DOTATOC alone or combined with [⁹⁰Y]Y-DOTATOC. [⁶⁸Ga]Ga-DOTATOC PET/CT was performed at baseline and 3 months after PRRT. For each PET/CT, we calculated SUVmax, SUVmean, somatostatin receptor expressing tumor volume (SRETV), and total lesion somatostatin receptor expression (TLSRE), as well as their percentage of changes (Δ), both for liver (_L) and for total tumor burden (_WB). Early clinical response (3 months after PRRT) and PFS were evaluated according to RECIST 1.1 and institutional NET board.

RESULTS

Early clinical response identified 9 partial response (PR), 25 stable disease (SD), and 5 progressive disease (PD). Post-SRETV_WB and ΔSRETV_WB were progressively increased among response groups (p = 0.02 and p = 0.03, respectively). Likewise, median post-SRETV_L was significantly higher in PD patients (p = 0.03). SUVmax and TLSRE did not correlate with early clinical response. Median PFS was 31 months. Patients with ΔSRETV_WB lower than -4.17% as well as those with post-SRETV_WB lower than 34.8 cm³ showed a longer PFS (p = 0.006 and p = 0.06, respectively). Finally, multivariate analysis identified ΔSRETV_WB as an independent predictor for PFS.

CONCLUSIONS

our results could strengthen the importance of evaluating the burden of disease on [⁶⁸Ga]Ga-DOTATOC PET/CT in NET patients treated with PRRT.

Detection of Bone Metastases by 68Ga-DOTA-SSAs and 18F-FDG PET/CT: A Two-Center Head-to-Head Study of Gastroenteropancreatic Neuroendocrine Neoplasms

Purpose

This study aimed to assess the efficacy of dual-tracer [⁶⁸Ga-DOTA-somatostatin receptor analogs (SSAs) and ¹⁸F-fluorodeoxyglucose (FDG)] positron emission tomography/computed tomography (PET/CT) imaging for detecting bone metastases (BMs) in patients with gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs).

Methods

We retrospectively enrolled 74 GEP-NEN patients with BMs from two centers, who underwent dual-tracer PET/CT from January 2014 to March 2021. We compared and analyzed effectiveness of the dual PET/CT imaging techniques on the BMs, based on ¹⁸F-FDG and ⁶⁸Ga-DOTA-SSAs. Specifically, we analyzed the imaging results using χ ² tests for classification variables, paired-sample tests for number of BMs, Wilcoxon's signed rank test for number of lesions, and the Kruskal-Wallis test for standard uptake value (SUV) ratio comparison. The correlation of dual-tracer SUVmax with Ki-67 index was analyzed by Spearman's correlation coefficient.

Results

The detection efficiencies of dual-tracer PET/CT imaging in patients with different pathologies showed discordant for detecting liver metastases and BMs in group neuroendocrine tumor (NET) G3, ⁶⁸Ga-DOTA-SSAs was better at detecting BMs for NET G3 (P=0.049 for SUV_T/B and P=0.026 for the number of metastatic lesions). In addition, statistical significance was found among osteogenesis group, osteolysis group, and the no-change group (for bone SUV_T/B value detected by ¹⁸F-FDG and Ki-67 index, osteogenesis group < osteolysis group; for bone SUV_T/B detected by ⁶⁸Ga-DOTA-SSAs, osteogenesis group > the no-change group). What is more, liver and bone SUVmax and Ki-67 index were positively correlated in ¹⁸F-FDG imaging (P < 0.001 for liver; P=0.002 for bone), and negatively correlated in ⁶⁸Ga-DOTA-SSAs imaging (P < 0.001 for liver; P=0.039 for bone).

Conclusions

⁶⁸Ga-DOTA-SSAs was superior to ¹⁸F-FDG for detecting BMs in NET G1/G2 (well and moderately differentiated NETs), as well as in NET G3 (poorly differentiated NETs). Relatively good differentiation was observed in the osteogenesis group. In addition, dual-tracer PET/CT imaging results were observably correlated with tumor differentiation.

Glucose Metabolism Modification Induced by Radioligand Therapy with [177Lu]Lu/[90Y]Y-DOTATOC in Advanced Neuroendocrine Neoplasms: A Prospective Pilot Study within FENET-2016 Trial

[18F]F-FDG (FDG) PET is emerging as a relevant diagnostic and prognostic tool in neuroendocrine neoplasms (NENs), as a simultaneous decrease in [68Ga]Ga-DOTA peptides and increase in FDG uptake (the “flip-flop” phenomenon) occurs during the natural history of these tumors. The aim of this study was to evaluate the variations on FDG PET in NEN patients treated with two different schemes of radioligand therapy (RLT) and to correlate them with clinical−pathologic variables. A prospective evaluation of 108 lesions in 56 patients (33 males and 23 females; median age, 64.5 years) affected by NENs of various primary origins (28 pancreatic, 13 gastrointestinal, 9 bronchial, 6 unknown primary (CUP-NENs) and 1 pheochromocytoma) and grades (median Ki-67 = 9%) was performed. The patients were treated with RLT within the phase II clinical trial FENET-2016 (CTID: NCT04790708). RLT was offered for 32 patients with the MONO scheme (five cycles of [177Lu]Lu-DOTATOC) and for 24 with the DUO scheme (three cycles of [177Lu]Lu-DOTATOC alternated with two cycles of [90Y]Y-DOTATOC). Variations in terms of the ΔSUVmax of a maximum of three target lesions per patient (58 for MONO and 50 for DUO RLT) were assessed between baseline and 3 months post-RLT FDG PET. In patients with negative baseline FDG PET, the three most relevant lesions on [68Ga]Ga-DOTA-peptide PET were assessed and matched on post-RLT FDG PET, to check for any possible changes in FDG avidity. Thirty-five patients (62.5%) had at least one pathological FDG uptake at the baseline scans, but the number was reduced to 29 (52%) after RLT. In the patients treated with DUO-scheme RLT, 20 out of 50 lesions were FDG positive before therapy, whereas only 14 were confirmed after RLT (p = 0.03). Moreover, none of the 30 FDG-negative lesions showed an increased FDG uptake after RLT. The lesions of patients with pancreatic and CUP-NENs treated with the DUO scheme demonstrated a significant reduction in ΔSUVmax in comparison to those treated with MONO RLT (p = 0.03 and p = 0.04, respectively). Moreover, we found a mild positive correlation between the grading and ΔSUVmax in patients treated with the MONO scheme (r = 0.39, p < 0.02), while no evidence was detected for patients treated with the DUO scheme. Our results suggest that RLT, mostly with the DUO scheme, could be effective in changing NEN lesions’ glycometabolism, in particular, in patients affected by pancreatic and CUP-NENs, regardless of their Ki-67 index. Probably, associating [90Y]Y-labelled peptides, which have high energy emission and a crossfire effect, and [177Lu]Lu ones, characterized by a longer half-life and a safer profile for organs at risk, might represent a valid option in FDG-positive NENs addressed to RLT. Further studies are needed to validate our preliminary findings. In our opinion, FDG PET/CT should represent a potent tool for fully assessing a patient’s disease characteristics, both before and after RLT.