Peptide Receptor Radionuclide Therapy as First-Line Systemic Treatment in Advanced Inoperable/Metastatic Neuroendocrine Tumors

Clinical characteristics and treatment patterns of patients with gastroenteropancreatic neuroendocrine neoplasia in Germany receiving peptide receptor radionuclide therapy: A real-world data registry-based study

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) are rare malignancies deriving from the endocrine system in the gastrointestinal tract including the pancreas. Prognosis is greatly heterogenous due to its dependency on various factors, most importantly stage and differentiation. Several studies report an alarming rise in incidence in the past decade. Despite there being some therapeutical options, best therapy sequence still needs to be defined, particularly for unresectable and/or intermediate and high-grade NENs. Peptide receptor radionuclide therapy (PRRT) was approved in Europe and USA in 2017 and 2018, respectively. Studies with real-world systematic data on characteristics and treatment patterns of PRRT-receiving patients was non-existent at the time of this writing. In this retrospective study, we identified within the German NET-Registry 203 patients diagnosed with GEP-NEN having received PRRT from 1995 to 2023. We assessed general clinical patient characteristics, disease-specific characteristics, treatments and outcomes. To obtain a more up-to-date picture of treatment modalities and outcomes, a subgroup of the study population was allocated to the "therapy cohort," defined by patients with date of first diagnosis between 2010 and 2023 (open cohort). Mean age of the study population was 58 years (SD 12 years) with 51.7% being men. Most patients had a WHO performance score of 0 to 1 (41.4% and 50.5%, respectively). Most NEN cases were of small intestine/pancreatic origin (46.3% and 45.3%, respectively) and displayed well/moderate differentiation (55.3%). Ki-67 was generally within the 3% to 20% range (57.92%). Most patients presented with metastasis at diagnosis (73.9%). Somatostatin analogs (SSAs), chemotherapy and surgery were the most common non-PRRT therapy options (65.3%, 60.2%, and 50.0%, respectively). PRRT was most often applied as third- or second-line therapy (42.3% and 36.6%, respectively), usually after surgery and/or SSA treatment. As PRRT had been administered using different regimens, tumor response evaluation showed mixed responses. Given the low sample size and considerable amount of missing response data, no correlation analysis between PRRT sequencing and tumor response could be performed. Overall, the clinical characteristics and treatment patterns tend to follow trends observed in other studies or medical guidelines. Finally, this study presents real-world data that more accurately describes GEP-NEN disease in Germany and treatment modalities after PRRT's approval.

Peptide receptor chemoradionuclide therapy for neuroendocrine neoplasms: A systematic review

Peptide receptor chemoradionuclide therapy (PRCRT), the addition of radiosensitising chemotherapy to peptide receptor radionuclide therapy (PRRT), has been used in individual centres for neuroendocrine neoplasms (NENs), but there are few data to date regarding its efficacy and safety. We conducted a systematic review to document the efficacy and side effect profile of this combination. We searched for studies including ≥5 patients with advanced NENs who received PRCRT. Major databases were searched and supplemented by handsearching of major conferences from 2019 to 2023. Data extracted included clinicopathological characteristics, trial setting and doses of chemotherapy and PRRT administered. Endpoints included overall survival (OS), progression-free survival (PFS) and adverse events (AEs); summarised qualitatively because of the marked heterogeneity in patient populations, trial designs and treatments administered. Eligible studies (24) included: 14 retrospective studies (643 patients) and 10 prospective studies (521 patients). For PRRT, most studies used 177Lu (n = 21), with combination 177Lu + 90Y (n = 2), 111In (n = 1) and 225Ac (n = 1). Chemotherapy regimens included capecitabine (n = 8), capecitabine and temozolomide (n = 5), 5-fluorouracil (n = 4) or a mixture of regimens (n = 6). Most studies included Grade 1-2 NENs. In prospective studies, median OS exceeded 2 years in most studies (range not reached by end of follow-up-86 months). In retrospective studies, median OS ranged from 7 months to 55 months and was not reached in many studies. PFS data ranged from 31 months-not reached in prospective cohorts and from 4 months-not reached in retrospective cohorts. Grade 3/4 AEs were commonly haematological, with majority being reversible or having no ongoing clinical impact. For advanced NENs, PRCRT treatment has demonstrated promising clinical outcomes and was well tolerated, although identified studies were heterogeneous. Further randomised trial data are required to clarify the place of this combination modality in the NEN treatment paradigm.

177Lu-DOTATATE Plus Capecitabine Versus 177Lu-DOTATATE Alone in Patients with Advanced Grade 1/2 Gastroenteropancreatic Neuroendocrine Tumors (LuCAP): A Randomized, Phase 2 Trial

177Lu-DOTATATE has emerged as a viable treatment strategy for advanced well-differentiated grade 1/2 gastroenteropancreatic neuroendocrine tumors (GEP-NETs). Few retrospective studies have shown concomitant 177Lu-DOTATATE with radiosensitizing low-dose capecitabine to be effective in advanced NETs. However, this has not been validated in prospective randomized-controlled trials. Methods: In this investigator-initiated, parallel-group, open-label, phase 2 trial, patients with grade 1/2 GEP-NETs, having progressive somatostatin receptor-positive, locally advanced, or metastatic disease on 68Ga-DOTANOC PET/CT, were randomly assigned in a 1:1 ratio to 177Lu-DOTATATE plus capecitabine (experimental arm) or 177Lu-DOTATATE only (control arm). 177Lu-DOTATATE was administered at approximately 7.4 GBq/cycle intravenously, for up to 4 cycles, at 8 wk intervals, whereas capecitabine was given at 1,250 mg/m2/d orally from day 0 to day 14 of each cycle of 177Lu-DOTATATE. The primary endpoint was the objective response rate. Secondary endpoints included the disease control rate, progression-free survival, overall survival, and adverse events. Results: Seventy-two patients (median age, 53 y; range, 18-79 y) were enrolled. The objective response rate was 33.3% (95% CI, 18.6-50.9%) in the experimental arm versus 30.6% (95% CI, 16.4-48.1%) in the control arm (P = 0.800). The disease control rate was 88.9% (95% CI, 73.9-96.9%) and 91.7% (95% CI, 77.5-98.2%) in the experimental and control arms, respectively (P = 1.000). The estimated median progression-free survival in the experimental arm was 29 mo (95% CI, 22-29 mo) versus 31 mo (95% CI, 29-32 mo) in the control arm (P = 0.401). The median overall survival was not reached in either arm (P = 0.876). Overall, adverse events of at least grade 3 were noted in 7 patients in the experimental arm versus 6 patients in the control arm (P = 0.759). Conclusion: Based on the results of this trial, the addition of low-dose capecitabine to 177Lu-DOTATATE in advanced grade 1/2 GEP-NETs did not lead to superior radiographic responses. Further studies are needed to evaluate its potential role in high-grade NETs.

Short-Term Biological Toxicity Prediction of [177Lu]Lutetium-Oxodotreotide: An Original Retrospective Analysis

Introduction: [177Lu]Lutetium (Lu)-oxodotreotide is a radiopharmaceutical drug used as peptide receptor radionuclide therapy (PRRT) for somatostatin receptor-expressing neuroendocrine neoplasms. It provides an additional effective alternative treatment for these rare cancers. Although well tolerated, its safety profile must continue to be characterized to support its use as a first-line treatment or for additional cycles. This study evaluated factors associated with the occurrence of [177Lu]Lu-oxodotreotide induced short-term toxicity. Materials and Methods: A retrospective observational monocentric study was carried out from July 2013 to October 2021. Inclusion criteria were defined as follows: patients who received at least four cycles of [177Lu]Lu-oxodotreotide and were followed up for 6 months after the last injection. Graduated toxicity was defined using the National Cancer Institute Common Terminology Criteria for Adverse Events 5.0. Cox regression was used in the analysis. Results: Forty patients were included. The most frequent toxicities occurred during the first cycle and were graded as G1 or G2. As expected, toxicities were predominantly hematological and hepatic, with incomplete reversibility after each cycle. The following factors were significantly related to the occurrence of hematological or hepatic toxicity during PRRT: gastrointestinal primary tumor diagnosis, bone metastases, peritoneal metastases, pancreatic metastases or pulmonary metastases, and high tumor grade. Conclusion: Knowledge and consideration of these factors in adjusting [177Lu]Lu-oxodotreotide treatment regimen could help prevent or reduce the severity of these toxicities. Further studies are still warranted to refine these results and improve treatment management.

Sunitinib in Tandem With 177 Lu-DOTATATE Therapy in Advanced Pancreatic Neuroendocrine Tumor : A New Treatment Approach

ABSTRACT

Various systemic treatment options are available for advanced pancreatic neuroendocrine tumors (NETs); however, individual treatment may be suboptimally effective. Sunitinib inhibits multiple kinases and signaling pathways with delay in tumor growth, whereas peptide radioreceptor therapy (PRRT) delivers targeted radiation to the tumors in pancreatic NETs. There is a dearth of literature on the combined or tandem use of these systemic treatment modalities. We present a case of 40-year-old man with advanced pancreatic NET where PRRT or sunitinib as monotherapy had a suboptimal treatment response, but the use of sunitinib in tandem with 177 Lu-PRRT reinforced the response to the treatment.

Peptide Receptor Radionuclide Therapy (PRRT): Innovations and Improvements

Neuroendocrine neoplasms (NENs) are tumors originating from neuroendocrine cells distributed throughout the human body. With an increasing incidence over the past few decades, they represent a highly heterogeneous group of neoplasms, mostly expressing somatostatin receptors (SSTRs) on their cell surface. Peptide receptor radionuclide therapy (PRRT) has emerged as a crucial strategy for treating advanced, unresectable neuroendocrine tumors by administering radiolabeled somatostatin analogs intravenously to target SSTRs. This article will focus on the multidisciplinary theranostic approach, treatment effectiveness (such as response rates and symptom relief), patient outcomes, and toxicity profile of PRRT for NEN patients. We will review the most significant studies, such as the phase III NETTER-1 trial, and discuss promising new radiopharmaceuticals, including alpha-emitting radionuclide-labeled somatostatin analogs and SSTR antagonists.

Peptide Receptor Radionuclide Therapy (PRRT): Innovations and Improvements

Neuroendocrine neoplasms (NENs) are tumors originating from neuroendocrine cells distributed throughout the human body. With an increasing incidence over the past few decades, they represent a highly heterogeneous group of neoplasms, mostly expressing somatostatin receptors (SSTRs) on their cell surface. Peptide receptor radionuclide therapy (PRRT) has emerged as a crucial strategy for treating advanced, unresectable neuroendocrine tumors by administering radiolabeled somatostatin analogs intravenously to target SSTRs. This article will focus on the multidisciplinary theranostic approach, treatment effectiveness (such as response rates and symptom relief), patient outcomes, and toxicity profile of PRRT for NEN patients. We will review the most significant studies, such as the phase III NETTER-1 trial, and discuss promising new radiopharmaceuticals, including alpha-emitting radionuclide-labeled somatostatin analogs and SSTR antagonists.

Gastro-Enteric-Pancreatic Neuroendocrine Tumor Treatment: Actinium-225-DOTATATE and Combined Therapies

The role of lutetium-177-DOTATATE in advanced well-differentiated gastro-entero-pancreatic neuroendocrine tumors is well established. However, there is a scope for improving treatment outcomes. Actinium-225-DOTATATE is a form of targeted alpha therapy (TAT) that results in more efficient tumor cell killing owing to the substantially higher linear energy transfer of alpha particles. Systemic TAT is also safe given that the shorter path length of the alpha particles spares the surrounding healthy tissue and results in relatively fewer adverse events. Combination therapies with radiosensitizing and other chemotherapeutic agents have also gained popularity, especially in the setting of higher grade and fluorodeoxyglucose-avid tumors.

Gastro-Enteric-Pancreatic Neuroendocrine Tumor Treatment: 177Lu-DOTATATE

177Lu-DOTA-TATE therapy is a highly effective therapy in metastatic, well-differentiated, somatostatin receptor-positive GEP-neuroendocrine tumors (NETs) with mostly tolerable adverse effects. Guidelines generally refer to peptide receptor radionuclide therapy as a second-line therapy after SSA in gastroenteric and second- or third-line therapy in pancreatic NETs to improve survival rates and quality of life. Although we do not have sufficient data, 177Lu-DOTA-TATE therapy may also have a role in high-grade NET therapy, mostly in combination with other treatments such as chemotherapy.

Surgery, Liver Directed Therapy and Peptide Receptor Radionuclide Therapy for Pancreatic Neuroendocrine Tumor Liver Metastases

Pancreatic neuroendocrine tumors (PNETs) are described by the World Health Organization (WHO) classification by grade (1–3) and degree of differentiation. Grade 1 and 2; well differentiated PNETs are often characterized as relatively “indolent” tumors for which locoregional therapies have been shown to be effective for palliation of symptom control and prolongation of survival even in the setting of advanced disease. The treatment of liver metastases includes surgical and non-surgical modalities with varying degrees of invasiveness; efficacy; and risk. Most of these modalities have not been prospectively compared. This paper reviews literature that has been published on treatment of pancreatic neuroendocrine liver metastases using surgery; liver directed embolization and peptide receptor radionuclide therapy (PRRT). Surgery is associated with the longest survival in patients with resectable disease burden. Liver-directed (hepatic artery) therapies can sometimes convert patients with borderline disease into candidates for surgery. Among the three embolization modalities; the preponderance of data suggests chemoembolization offers superior radiographic response compared to bland embolization and radioembolization; but all have similar survival. PRRT was initially approved as salvage therapy in patients with advanced disease that was not amenable to resection or embolization; though the role of PRRT is evolving rapidly

Predictive Factors for Resistant Disease with Medical/Radiologic/Liver-Directed Anti-Tumor Treatments in Patients with Advanced Pancreatic Neuroendocrine Neoplasms: Recent Advances and Controversies

Purpose: Recent advances in the diagnosis, management and nonsurgical treatment of patients with advanced pancreatic neuroendocrine neoplasms (panNENs) have led to an emerging need for sensitive and useful prognostic factors for predicting responses/survival. Areas covered: The predictive value of a number of reported prognostic factors including clinically-related factors (clinical/laboratory/imaging/treatment-related factors), pathological factors (histological/classification/grading), and molecular factors, on therapeutic outcomes of anti-tumor medical therapies with molecular targeting agents (everolimus/sunitinib/somatostatin analogues), chemotherapy, radiological therapy with peptide receptor radionuclide therapy, or liver-directed therapies (embolization/chemoembolization/radio-embolization (SIRTs)) are reviewed. Recent findings in each of these areas, as well as remaining controversies and uncertainties, are discussed in detail, particularly from the viewpoint of treatment sequencing. Conclusions: The recent increase in the number of available therapeutic agents for the nonsurgical treatment of patients with advanced panNENs have raised the importance of prognostic factors predictive for therapeutic outcomes of each treatment option. The establishment of sensitive and useful prognostic markers will have a significant impact on optimal treatment selection, as well as in tailoring the therapeutic sequence, and for maximizing the survival benefit of each individual patient. In the paper, the progress in this area, as well as the controversies/uncertainties, are reviewed.

Therapeutic strategies for gastroenteropancreatic neuroendocrine neoplasms: State-of-the-art and future perspectives

Although gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) have always been considered rare tumors, their incidence has risen over the past few decades. They represent a highly heterogeneous group of neoplasms with several prognostic factors, including disease stage, proliferative index (Ki67), and tumor differentiation. Most of these neoplasms express somatostatin receptors on the cell surface, a feature that has important implications in terms of prognosis, diagnosis, and therapy. Although International Guidelines propose algorithms aimed at guiding therapeutic strategies, GEP-NEN patients are still very different from one another, and the need for personalized treatment continues to increase. Radical surgery is always the best option when feasible; however, up to 80% of cases are metastatic upon diagnosis. Regarding medical treatments, as GEP-NENs are characterized by relatively long overall survival, multiple therapy lines are adopted during the lifetime of these patients, but the optimum sequence to be followed has never been clearly defined. Furthermore, although new molecular markers aimed at predicting the response to therapy, as well as prognostic scores, are currently being studied, their application is still far from being part of daily clinical practice. As they represent a complex disease, with therapeutic protocols that are not completely standardized, GEP-NENs require a multidisciplinary approach. This review will provide an overview of the available therapeutic options for GEP-NENs and attempts to clarify the possible approaches for the management of these patients and to discuss future perspectives in this field.

Hematological Markers as Predictors of Treatment Outcomes with Lutetium 177 (177Lu)-DOTATATE in Patients with Advanced Neuroendocrine Tumors

Background: Chronic inflammation has been linked to the development and prognosis of neuroendocrine tumors (NETs). The current study intended to evaluate the role of peripheral hematological inflammatory markers, viz. the platelet-lymphocyte ratio (PLR), neutrophil-lymphocyte ratio, and monocyte-lymphocyte ratio, as predictors of treatment outcomes in patients with advanced NETs after Lutetium-177(177Lu)-DOTATATE therapy. Materials and Methods: Data of consecutive patients with advanced metastatic and/or inoperable NETs treated with 177Lu-DOTATATE from the year 2012 to 2019 at the authors' center were retrospectively analyzed. Results: Forty-two NET patients (median age: 49.5 years) received a median cumulative activity of 29.6 GBq of 177Lu-DOTATATE over 2-5 cycles at 8-12-week intervals. The median progression-free survival (PFS) of the study cohort was 30 months (95% confidence interval, CI: 18.2-41.9 months). A baseline PLR ≥173.1 was found to be a significant predictor of poor PFS with a univariate hazard ratio of 3.82 (95% CI: 1.21-12.03); however, the association was not significant on multivariate analysis. The median overall survival was not reached and none of the parameters were significantly associated with it. Conclusions: A higher baseline PLR was shown to be associated with a negative outcome on PFS after 177Lu-DOTATATE therapy and is a promising marker for future larger studies.

Alpha Before Beta: Exceptional Response to First-Line 225Ac-DOTATATE in a Patient of Metastatic Neuroendocrine Tumor With Extensive Skeletal Involvement

ABSTRACT

The utility of β-emitter 177Lu-DOTATATE in patients of neuroendocrine tumors (NETs) with widespread skeletal metastases is limited by its relatively modest response rates and a significant concern for hematotoxicity. In such situations, targeted α therapy with 225Ac-DOTATATE can be potentially beneficial. In this report, a 46-year-old man with rectal NET and extensive skeletal metastases was treated upfront with 6 cycles of 225Ac-DOTATATE at 8 weeks' intervals. The patient showed excellent symptomatic, biochemical, and radiological response with no grade 3/4 adverse events. The first-line use of 225Ac-DOTATATE, therefore, presents a novel strategy for metastatic NETs with high skeletal disease burden.

Theranostic Options for Radioiodine-Refractory Differentiated Thyroid Carcinoma: Recent Advances, Challenges, and Road Ahead

Radioiodine-refractory differentiated thyroid cancer (RAIR-DTC), though uncommon, presents a considerable therapeutic challenge with poor long-term outcomes. Currently, tyrosine kinase inhibitors are the mainstay of treatment for advanced RAIR-DTC patients. However, these agents are associated with a multitude of adverse events with resultant deterioration in the quality-of-life of the patients. Targeted theranostic approaches with radiolabelled integrin binders and fibroblast activation protein- (FAP)-inhibitors seem to have a promising role in the management of such patients. This mini-review focuses on these novel theranostic strategies in RAIR-DTC, with emphasis on recent advances, existing challenges, and future directions.

177Lu-DOTATATE Plus Radiosensitizing Capecitabine Versus Octreotide Long-Acting Release as First-Line Systemic Therapy in Advanced Grade 1 or 2 Gastroenteropancreatic Neuroendocrine Tumors: A Single-Institution Experience

PURPOSE

To compare the efficacy and safety of 177Lu-DOTATATE plus radiosensitizing capecitabine and octreotide long-acting release (LAR) as first-line systemic therapy in advanced well-differentiated gastroenteropancreatic neuroendocrine tumors (GEP-NETs).

MATERIALS AND METHODS

Data of consecutive patients of advanced inoperable or metastatic grade 1 or 2 GEP-NETs treated with first-line 177Lu-DOTATATE plus radiosensitizing capecitabine or octreotide LAR from September 2012 to December 2019 were collected and analyzed for response, toxicity, and survival outcomes.

RESULTS

Seventy-six patients (median age: 53 years; range 14-81 years) with treatment-naïve advanced grade 1 or 2 GEP-NETs were included. Thirty-six patients received a median cumulative dose of 27.3 GBq of 177Lu-DOTATATE intravenously at 8-12 weeks' intervals along with 1,250 mg/m2 oral capecitabine on days 0-14 of each cycle of 177Lu-DOTATATE, whereas 40 patients were administered 30 mg octreotide LAR intramuscularly every 4 weeks. Using response evaluation criteria in solid tumor 1.1, the objective response rate was 38% in the 177Lu-DOTATATE arm compared with 15% in the octreotide LAR arm (P = .025), whereas the disease control rates were 88% and 67% in 177Lu-DOTATATE and octreotide LAR arms, respectively (P = .035). The median durations of progression-free survival in the 177Lu-DOTATATE and octreotide LAR arms were 54 months and 16 months, respectively (P = .017), whereas the median overall survival was not reached and not significantly different across both the arms. Of the treatment-related adverse events, no major difference was observed in the occurrence of grade 3 or 4 toxicities between the two treatment arms.

CONCLUSION

First-line systemic 177Lu-DOTATATE plus radiosensitizing capecitabine achieved better radiologic response and longer progression-free survival compared with octreotide LAR in patients with advanced grade 1 or 2 GEP-NETs. Future randomized controlled trials are, however, required to determine the best treatment sequence for the treatment-naïve patients with advanced GEP-NETs.

Strategies Towards Improving Clinical Outcomes of Peptide Receptor Radionuclide Therapy

PURPOSE OF REVIEW

Peptide receptor radionuclide therapy (PRRT) with [177Lu-DOTA0,Tyr3] octreotate is an effective and safe second- or third-line treatment option for patients with low-grade advanced gastroenteropancreatic (GEP) neuroendocrine neoplasms (NEN). In this review, we will focus on possible extensions of the current use of PRRT and on new approaches which could further improve its treatment efficacy and safety.

RECENT FINDINGS

Promising results were published regarding PRRT in other NENs, including lung NENs or high-grade NENs, and applying PRRT as neoadjuvant or salvage therapy. Furthermore, a diversity of strategic approaches, including dosimetry, somatostatin receptor antagonists, somatostatin receptor upregulation, radiosensitization, different radionuclides, albumin binding, alternative renal protection, and liver-directed therapy in combination with PRRT, have the potential to improve the outcome of PRRT. Also, novel biomarkers are presented that could predict response to PRRT. Multiple preclinical and early clinical studies have shown encouraging potential to advance the clinical outcome of PRRT in NEN patients. However, at this moment, most of these strategies have not yet reached the clinical setting of randomized phase III trials.