Safety and efficacy of peptide receptor radionuclide therapy in neuroendocrine tumors: A single center experience

Peptide receptor radionucleotide therapy (PRRT) with 177Lu-dotatate is widely used for the treatment of patients with neuroendocrine tumors (NETs). We analyzed data from 104 patients with NETs treated with 177Lu -dotatate at a US academic center between December 2017 and October 2020 to better understand patterns of long-term efficacy, safety, and toxicity in the real-world setting. 177Lu-dotatate (200 mCi) was administered every eight weeks for four doses. The most common sites of primary disease were small intestine NETs (n = 49, 47%), pancreatic NETs (n = 32, 31%), and lung NETs (n = 7, 7%). Twenty-seven percent had Ki-67 <3%, 49% had Ki-67 between 3-20%, and 13.5% had Ki-67 >20%. The cohort had been pretreated with a median of two prior lines of treatment. Forty percent had received prior liver-directed treatment. Seventy-four percent of patients completed all four doses of treatment. The objective response rate was 18%. The median time-to-treatment failure/death was significantly longer for small-bowel NETs when compared to pancreatic NETs (37.3 months vs. 13.2 months, p = 0.001). In a multivariate model, Ki-67, primary site, and liver tumor burden ≥50% were found to independently predict time-to-treatment failure/death. Around 40% of patients experienced adverse events of ≥grade 3 severity. Treatment-related adverse events leading to discontinuation of therapy happened in 10% of patients. Preexisting mesenteric/peritoneal disease was present in 33 patients; seven of these patients developed bowel-related toxicities including two grade 5 events. We also report two cases of delayed-onset minimal change nephrotic syndrome, which occurred 14 and 27 months after the last dose of PRRT. Lastly, we describe six patients who developed rapid tumor progression in the liver leading to terminal liver failure within 7.3 months from the start of PRRT, and identify potential risk factors associated with this occurrence, which will need further study.

Effectiveness and Safety of Retreatment with 177Lu-DOTATATE in Patients with Progressive Neuroendocrine Tumors: A Retrospective Real-World Study in the United States

Advanced neuroendocrine tumors (NETs) are associated with a poor prognosis. A regimen of 4 cycles of 177Lu-DOTATATE has been shown to improve both progression-free survival (PFS) and overall survival (OS) in patients with advanced NETs. To the best of our knowledge, this is the first study in the United States to evaluate the effectiveness and safety of additional cycles of 177Lu-DOTATATE therapy in patients with progressive NETs. Methods: This was a retrospective chart review of adults with advanced NETs. The patients had undergone initial treatment with up to 4 cycles of 177Lu-DOTATATE and, after disease progression and a period of at least 6 mo since the end of the initial treatment, were retreated with at least 1 additional cycle at a single center (2010-2020). Patient characteristics, treatment patterns, and clinical outcomes were evaluated descriptively. Response was evaluated according to RECIST 1.1; toxicity was defined using criteria from Common Terminology Criteria for Adverse Events, version 5.0. Kaplan-Meier plots were used to evaluate PFS and OS. Results: Of the 31 patients who received 177Lu-DOTATATE retreatment, 61% were male and 94% were White. Overall, patients received a median of 6 cycles (4 initial cycles and 2 retreatment cycles), and the mean administered activity was 41.9 GBq. Two patients also went on to receive additional retreatment (1 and 2 cycles, individually) after a second period of at least 6 mo and progression after retreatment. Best responses of partial response and stable disease were observed in 35% and 65% of patients after the initial treatment and 23% and 45% of patients after retreatment, respectively. The median PFS after the initial treatment was 20.2 mo and after retreatment was 9.6 mo. The median OS after the initial treatment was 42.6 mo and after retreatment was 12.6 mo. Hematologic parameters decreased significantly during both the initial treatment and retreatment but recovered such that there was little difference between the values before the initial treatment and before the retreatment. Clinically significant hematotoxicity occurred in 1 and 3 patients after the initial treatment and retreatment, respectively. No grade 3 or 4 nephrotoxicity was observed. Conclusion: Retreatment with 177Lu-DOTATATE after progression appeared to be well tolerated and offered disease control in patients with progressive NETs after initial 177Lu-DOTATATE treatment.

[Current developments in the treatment of neuroendocrine tumors]

BACKGROUND

Well-differentiated neuroendocrine tumors (NET) are rare malignancies that are clinically very heterogeneous. Accordingly, their treatment is also complex and dependent on various factors. With currently available systemic therapies, the prognosis is often favorable.

OBJECTIVES

This article aims to provide an overview of current treatment strategies for NET, addressing the most important NET locations.

METHODS

The current European guidelines and further relevant literature on the treatment of NET were reviewed for this purpose.

RESULTS

The therapeutic spectrum for NET is extremely broad: For NET of the stomach/duodenum, appendix, and rectum, endoscopic or surgical resection is often sufficient, and metastatic tumors are rare. NET of the pancreas, small intestine and lung should also undergo potentially curative resection in the early stages. In the metastatic stage, locoregional treatments such as surgery and liver tumor embolization play a role. Major advances have been made in drug therapy, with somatostatin analogs (octreotide and lanreotide), an mTOR inhibitor (everolimus), and a tyrosine kinase inhibitor (sunitinib) being widely used. Peptide receptor radionuclide therapy (PRRT) is also an invaluable option. In some cases, classic chemotherapy is indicated.

CONCLUSIONS

Many effective therapies are now available for NET. It is important to select the right therapy at the right time for each patient through interdisciplinary management.

Current and emerging strategies for the management of advanced/metastatic lung neuroendocrine tumors

Pulmonary neuroendocrine tumors represent a spectrum of disease ranging from typical carcinoid tumors to small cell lung cancers. The incidence of low-grade pulmonary NETs has been increasing, leading to improved awareness and the need for more treatment options for this rare cancer. Somatostatin analogs continue to be the backbone of therapy and may be followed or accompanied by targeted therapy, chemotherapy, and immune therapy. The recent addition of peptide receptor radionuclide therapy (PRRT) to the treatment armamentarium of NETs has led to the development of targeted alpha therapy to overcome PRRT resistance and minimize off-target adverse effects. Herein, we aim to highlight current treatment options for patients with advanced low grade pulmonary NETs along with emerging therapies, sequencing of therapies, upcoming clinical trials, and the importance of a multidisciplinary team to improve patient outcomes.

From biology to clinical practice: antiproliferative effects of somatostatin analogs in neuroendocrine neoplasms

Somatostatin analogs (SSA), specifically octreotide and lanreotide, have demonstrated antiproliferative effects in patients with neuroendocrine tumors (NET), a group of rare malignancies of diverse origin and presentation. A prominent feature of NET cells is the expression of G protein-coupled receptors called somatostatin receptors (SSTR). Although these SSTR are not uniformly present in NET, they can be instrumental in the diagnosis and treatment of NET. Apart from their application in nuclear imaging and radionuclide therapy, SSA have proven invaluable in the treatment of hormonal syndromes associated with certain NET (antisecretory effects of SSA), but it took more than two decades to convincingly demonstrate the antiproliferative effects of SSA in metastatic NET with the two pivotal studies PROMID and CLARINET. The current review summarizes three decades of SSA treatment and provides an overview of the clinical trial landscape for SSA monotherapy and combination therapy, including clinical implications and quality of life aspects, as well as ongoing fields of research.

Theranostic Innovation by Humane N-of-One Cancer Care in Real-World Patients

Patients with relapsed or refractory metastatic cancer unresponsive to standard therapies have motivated nuclear physicians to develop innovative radioligands, precisely targeted to tumor molecular receptors, for effective treatment of specific advanced malignancies. Individual practitioners in departments of nuclear medicine across the world have performed first-in-human studies on compassionate patient usage N-of-One protocols. These physician-sponsored studies then evolved into early-phase clinical trials and obtained real-world data to demonstrate real-world evidence of effectiveness in prolonging survival and enhancing quality of life of many so-called "End-Stage" cancer patients. Virtually all the therapeutic radiopharmaceuticals in current clinical oncology have been discovered and developed into effective specific treatments of targetable cancers by individual doctors in the course of their hospital practice. Pharma industry was not involved until many years later when performance of mandated Phase 3 randomized controlled trials became necessary to achieve regulatory agency approval. This article traces the history of several novel theranostic agents developed from compassionate N-of-One studies by hospital physicians over the past 36 years. It acknowledges the collegiality and collaboration of individual nuclear medicine specialists, worldwide, in pioneering effective humane therapy of particular advanced cancers unresponsive to conventional treatments.

A radiomic- and dosiomic-based machine learning regression model for pretreatment planning in 177 Lu-DOTATATE therapy

BACKGROUND

Standardized patient-specific pretreatment dosimetry planning is mandatory in the modern era of nuclear molecular radiotherapy, which may eventually lead to improvements in the final therapeutic outcome. Only a comprehensive definition of a dosage therapeutic window encompassing the range of absorbed doses, that is, helpful without being detrimental can lead to therapy individualization and improved outcomes. As a result, setting absorbed dose safety limits for organs at risk (OARs) requires knowledge of the absorbed dose-effect relationship. Data sets of consistent and reliable inter-center dosimetry findings are required to characterize this relationship.

PURPOSE

We developed and standardized a new pretreatment planning model consisting of a predictive dosimetry procedure for OARs in patients with neuroendocrine tumors (NETs) treated with 177 Lu-DOTATATE (Lutathera). In the retrospective study described herein, we used machine learning (ML) regression algorithms to predict absorbed doses in OARs by exploiting a combination of radiomic and dosiomic features extracted from patients' imaging data.

METHODS

Pretreatment and posttreatment data for 20 patients with NETs treated with 177 Lu-DOTATATE were collected from two clinical centers. A total of 3412 radiomic and dosiomic features were extracted from the patients' computed tomography (CT) scans and dose maps, respectively. All dose maps were generated using Monte Carlo simulations. An ML regression model was designed based on ML algorithms for predicting the absorbed dose in every OAR (liver, left kidney, right kidney, and spleen) before and after the therapy and between each therapy session, thus predicting any possible radiotoxic effects.

RESULTS

We evaluated nine ML regression algorithms. Our predictive model achieved a mean absolute dose error (MAE, in Gy) of 0.61 for the liver, 1.58 for the spleen, 1.30 for the left kidney, and 1.35 for the right kidney between pretherapy 68 Ga-DOTATOC positron emission tomography (PET)/CT and posttherapy 177 Lu-DOTATATE single photon emission (SPECT)/CT scans. Τhe best predictive performance observed was based on the gradient boost for the liver, the left kidney and the right kidney, and on the extra tree regressor for the spleen. Evaluation of the model's performance according to its ability to predict the absorbed dose in each OAR in every possible combination of pretherapy 68 Ga-DOTATOC PET/CT and any posttherapy 177 Lu-DOTATATE treatment cycle SPECT/CT scans as well as any 177 Lu-DOTATATE SPECT/CT treatment cycle and the consequent 177 Lu-DOTATATE SPECT/CT treatment cycle revealed mean absorbed dose differences ranges from -0.55 to 0.68 Gy. Incorporating radiodosiomics features from the 68 Ga-DOTATOC PET/CT and first 177 Lu-DOTATATE SPECT/CT treatment cycle scans further improved the precision and minimized the standard deviation of the predictions in nine out of 12 instances. An average improvement of 57.34% was observed (range: 17.53%-96.12%). However, it's important to note that in three instances (i.e., Ga,C.1 → C3 in spleen and left kidney, and Ga,C.1 → C2 in right kidney) we did not observe an improvement (absolute differences of 0.17, 0.08, and 0.05 Gy, respectively). Wavelet-based features proved to have high correlated predictive value, whereas non-linear-based ML regression algorithms proved to be more capable than the linear-based of producing precise prediction in our case.

CONCLUSIONS

The combination of radiomics and dosiomics has potential utility for personalized molecular radiotherapy (PMR) response evaluation and OAR dose prediction. These radiodosiomic features can potentially provide information on any possible disease recurrence and may be highly useful in clinical decision-making, especially regarding dose escalation issues.

Radiometals in Imaging and Therapy: Highlighting Two Decades of Research

The present article highlights the important progress made in the last two decades in the fields of molecular imaging and radionuclide therapy. Advancements in radiometal-based positron emission tomography, single photon emission computerized tomography, and radionuclide therapy are illustrated in terms of their production routes and ease of radiolabeling. Applications in clinical diagnostic and radionuclide therapy are considered, including human studies under clinical trials; their current stages of clinical translations and findings are summarized. Because the metalloid astatine is used for imaging and radionuclide therapy, it is included in this review. In regard to radionuclide therapy, both beta-minus (β-) and alpha (α)-emitting radionuclides are discussed by highlighting their production routes, targeted radiopharmaceuticals, and current clinical translation stage.

Neuroendocrine carcinoma of tonsil presented with axillary lymph node metastasis: Management dilemma

ABSTRACT

High-grade neuroendocrine carcinoma (NEC) of the tonsil is rare and has a poor prognosis. The usual presentation is a neck mass with locoregional cervical lymphadenopathy. An axillary lymphadenopathy as a primary presentation of NEC of the tonsils is uncommon and challenging to treat. Tonsil neuroendocrine tumors display aggressive behaviors associated with early recurrence and metastasis after surgical resection. Managing this condition is demanding compared to NECs of gastrointestinal origin since, to date, the management of head-and-neck neuroendocrine tumors is still not well established. We present a 49-year-old female with a rare case of NEC of the tonsil presenting primarily with axillary lymph nodes metastasis. The patient's axillary lymph node was biopsied and revealed a Grade III neuroendocrine tumor. A positron emission tomography (PET) scan was done in searching of a primary lesion and showed a highly metabolic mass of the left tonsil as well as a left axillary lymph node suggestive of metastasis. The patient has been managed with a multimodality approach, with a combination of chemotherapy regimen and surgical resection of the axillary lymph node. Subsequent PET scan evaluation showed a complete response of the primary tumor with residual left axillary lymph node metastasis. NECs of tonsil presented with axillary lymph nodes metastasis is rare and has a poor prognostic outcome. It poses a dilemma with regard to management, as surgical resection of the metastasis is not promising given the possibility of early recurrence.

Peptide-Based Agents for Cancer Treatment: Current Applications and Future Directions

Peptide-based strategies have received an enormous amount of attention because of their specificity and applicability. Their specificity and tumor-targeting ability are applied to diagnosis and treatment for cancer patients. In this review, we will summarize recent advancements and future perspectives on peptide-based strategies for cancer treatment. The literature search was conducted to identify relevant articles for peptide-based strategies for cancer treatment. It was performed using PubMed for articles in English until June 2023. Information on clinical trials was also obtained from ClinicalTrial.gov. Given that peptide-based strategies have several advantages such as targeted delivery to the diseased area, personalized designs, relatively small sizes, and simple production process, bioactive peptides having anti-cancer activities (anti-cancer peptides or ACPs) have been tested in pre-clinical settings and clinical trials. The capability of peptides for tumor targeting is essentially useful for peptide-drug conjugates (PDCs), diagnosis, and image-guided surgery. Immunomodulation with peptide vaccines has been extensively tested in clinical trials. Despite such advantages, FDA-approved peptide agents for solid cancer are still limited. This review will provide a detailed overview of current approaches, design strategies, routes of administration, and new technological advancements. We will highlight the success and limitations of peptide-based therapies for cancer treatment.

The relationship between tumour dosimetry, response, and overall survival in patients with unresectable Neuroendocrine Neoplasms (NEN) treated with 177Lu DOTATATE (LuTate)

Peptide Receptor Radionuclide Therapy (PRRT) delivers targeted radiation to Somatostatin Receptor (SSR) expressing Neuroendocrine Neoplasms (NEN). We sought to assess the predictive and prognostic implications of tumour dosimetry with respect to response by 68 Ga DOTATATE (GaTate) PET/CT molecular imaging tumour volume of SSR (MITVSSR) change and RECIST 1.1, and overall survival (OS).

METHODS

Patients with gastro-entero-pancreatic (GEP) NEN who received LuTate followed by quantitative SPECT/CT (Q-SPECT/CT) the next day (Jul 2010 to Jan 2019) were retrospectively reviewed. Single time-point (STP) lesional dosimetry was performed for each cycle using population-based pharmacokinetic modelling. MITVSSR and RECIST 1.1 were measured at 3-months post PRRT.

RESULTS

Median of 4 PRRT cycles were administered to 90 patients (range 2-5 cycles; mean 27.4 GBq cumulative activity; mean 7.6 GBq per cycle). 68% received at least one cycle with radiosensitising chemotherapy (RSC). RECIST 1.1 partial response was 24%, with 70% stable and 7% progressive disease. Cycle 1 radiation dose in measurable lesions was associated with local response (odds ratio 1.5 per 50 Gy [95% CI: 1.1-2.0], p = 0.002) when adjusted by tumour grade and RSC. Median change in MITVSSR was -63% (interquartile range -84 to -29), with no correlation with radiation dose to the most avid lesion on univariable or multivariant analyses (5.6 per 10 Gy [95% CI: -1.6, 12.8], p = 0.133). OS at 5-years was 68% (95% CI: 56-78%). Neither baseline MITVSSR (hazard ratio 1.1 [95% CI: 1.0, 1.2], p = 0.128) nor change in baseline MITVSSR (hazard ratio 1.0 [95% CI: 1.0, 1.1], p = 0.223) were associated with OS when adjusted by tumour grade and RSC but RSC was (95% CI: 0.2, 0.8, p = 0.012).

CONCLUSION

Radiation dose to tumour during PRRT was predictive of radiologic response but not survival. Survival outcomes may relate to other biological factors. There was no evidence that MITVSSR change was associated with OS, but a larger study is needed.

Next generation radiotheranostics promoting precision medicine

Radiotheranostics is a field of rapid growth with some approved treatments including 131I for thyroid cancer, 223Ra for osseous metastases, 177Lu-DOTATATE for neuroendocrine tumors, and 177Lu-PSMA (prostate-specific membrane antigen) for prostate cancer, and several more under investigation. In this review, we will cover the fundamentals of radiotheranostics, the key clinical studies that have led to current success, future developments with new targets, radionuclides and platforms, challenges with logistics and reimbursement and, lastly, forthcoming considerations regarding dosimetry, identifying the right line of therapy, artificial intelligence and more.

Preclinical Evaluation of [155/161Tb]Tb-Crown-TATE—A Novel SPECT Imaging Theranostic Agent Targeting Neuroendocrine Tumours

Terbium radioisotopes (149Tb, 152Tb, 155Tb, 161Tb) offer a unique class of radionuclides which encompass all four medicinally relevant nuclear decay modalities (α, β+, γ, β−/e−), and show high potential for the development of element-matched theranostic radiopharmaceuticals. The goal of this study was to design, synthesise, and evaluate the suitability of crown-TATE as a new peptide-conjugate for radiolabelling of [155Tb]Tb3+ and [161Tb]Tb3+, and to assess the imaging and pharmacokinetic properties of each radiotracer in tumour-bearing mice. [155Tb]Tb-crown-TATE and [161Tb]Tb-crown-TATE were prepared efficiently under mild conditions, and exhibited excellent stability in human serum (>99.5% RCP over 7 days). Longitudinal SPECT/CT images were acquired for 155Tb- and 161Tb- labelled crown-TATE in male NRG mice bearing AR42J tumours. The radiotracers, [155Tb]Tb-crown-TATE and [161Tb]Tb-crown-TATE, showed high tumour targeting (32.6 and 30.0 %ID/g, respectively) and minimal retention in non-target organs at 2.5 h post-administration. Biodistribution studies confirmed the SPECT/CT results, showing high tumour uptake (38.7 ± 8.0 %ID/g and 38.5 ± 3.5 %ID/g, respectively) and favourable tumour-to-background ratios. Blocking studies further confirmed SSTR2-specific tumour accumulation. Overall, these findings suggest that crown-TATE has great potential for element-matched molecular imaging and radionuclide therapy using 155Tb and 161Tb.

225Ac-Labeled Somatostatin Analogs in the Management of Neuroendocrine Tumors: From Radiochemistry to Clinic

The widespread use of peptide receptor radionuclide therapy (PRRT) represents a major therapeutic breakthrough in nuclear medicine, particularly since the introduction of ¹⁷⁷Lu-radiolabeled somatostatin analogs. These radiopharmaceuticals have especially improved progression-free survival and quality of life in patients with inoperable metastatic gastroenteropancreatic neuroendocrine tumors expressing somatostatin receptors. In the case of aggressive or resistant disease, the use of somatostatin derivatives radiolabeled with an alpha-emitter could provide a promising alternative. Among the currently available alpha-emitting radioelements, actinium-225 has emerged as the most suitable candidate, especially regarding its physical and radiochemical properties. Nevertheless, preclinical and clinical studies on these radiopharmaceuticals are still few and heterogeneous, despite the growing momentum for their future use on a larger scale. In this context, this report provides a comprehensive and extensive overview of the development of ²²⁵Ac-labeled somatostatin analogs; particular emphasis is placed on the challenges associated with the production of ²²⁵Ac, its physical and radiochemical properties, as well as the place of ²²⁵Ac-DOTATOC and ²²⁵Ac-DOTATATE in the management of patients with advanced metastatic neuroendocrine tumors.

Requirements for Meaningful Progress in the Therapy of Neuroendocrine Cancers

This Viewpoint discusses the role of data interpretation and clinical trial design in improving therapy of neuroendocrine cancers.

Systemic Therapy for Pancreatic Neuroendocrine Tumors

Patients with metastatic or advanced pancreatic neuroendocrine tumors (NETs) carry poorer prognoses relative to patients with other NETs due to bulkier and often, more proliferative baseline disease. Patients with these tumors also possess more approved treatment options relative to patients with other NETs, making therapeutic sequencing nuanced. As such, defining optimal therapeutic sequencing and developing more potent cytoreductive treatments for patients are significant areas of research need in the field. Herein this review, we discuss the current systemic therapy landscape, our approach to therapeutic sequencing in the clinic and ongoing studies seeking to define optimal sequencing of systemic therapies, and novel therapeutics in development, for patients with pancreatic NETs. We limit the scope of this latter topic to agents with preclinical or clinical rationale over the last 8 years to provide a contemporary view of the drug development landscape and focus primarily on new types of peptide receptor radionuclide therapy, anti-vascular endothelial growth factor receptor tyrosine kinase inhibitors and anti-vascular endothelial growth receptor tyrosine kinase inhibitor plus immunotherapy combinations.

Current and upcoming radionuclide therapies in the direction of precision oncology: A narrative review

As new molecular tracers are identified to target specific receptors, tissue, and tumor types, opportunities arise for the development of both diagnostic tracers and their therapeutic counterparts, termed "theranostics." While diagnostic tracers utilize positron emitters or gamma-emitting radionuclides, their theranostic counterparts are typically bound to beta and alpha emitters, which can deliver specific and localized radiation to targets with minimal collateral damage to uninvolved surrounding structures. This is an exciting time in molecular imaging and therapy and a step towards personalized and precise medicine in which patients who were either without treatment options or not candidates for other therapies now have expanded options, with tangible data showing improved outcomes. This manuscript explores the current state of theranostics, providing background, treatment specifics, and toxicities, and discusses future potential trends.

A Primer on Radiopharmaceutical Therapy

The goal of this article is to serve as a primer for the United States-based radiation oncologist who may be interested in learning more about radiopharmaceutical therapy (RPT). Specifically, we define RPT, review the data behind its current and anticipated indications, and discuss important regulatory considerations for incorporating it into clinical practice. RPT represents an opportunity for radiation oncologists to leverage 2 key areas of expertise, namely therapeutic radiation therapy and oncology, and apply them in a distinct context in collaboration with nuclear medicine and medical oncology colleagues. Although not every radiation oncologist will incorporate RPT into their day-to-day practice, it is important to understand the role for this modality and how it can be appropriately used in select patients.

Use of imaging-based dosimetry for personalising radiopharmaceutical therapy of cancer

Theranostics - i.e., the combination of molecular imaging and radiopharmaceutical therapy of cancer targeting a common biological feature - is a rapidly expanding field owing the recent successes of novel radiopharmaceutical therapies, such as ¹⁷⁷Lu-based prostate-specific membrane antigen radioligand therapy of prostate cancer and peptide receptor radionuclide therapy of neuroendocrine tumours. Despite the ongoing technical developments in imaging-based dosimetry, the existence of tumour absorbed dose-efficacy and organ absorbed dose-toxicity relationships, as well as the high interpatient variability in absorbed doses per unit activity, radiopharmaceutical therapies are still mostly administered in a fixed-activity, one-size-fits-all fashion. This is at odds with the principles of radiation oncology, where the absorbed doses to tissues are prescribed and their delivery is carefully planned and controlled for each individual patient to maximise the clinical benefits. There is a growing body of clinical evidence that dosimetry-based radiopharmaceutical therapy allows to safely optimise tumour irradiation, which translates into improved clinical outcomes. In this narrative review, we will present the reported prospective clinical experience to date on the use of imaging-based dosimetry to personalise radiopharmaceutical therapies.

Treatment Sequencing Strategies in Advanced Neuroendocrine Tumors: A Review

Neuroendocrine tumor (NET) incidence has grown. The treatment landscape for advanced NETs is rapidly evolving, but there are limited head-to-head data to guide treatment sequencing decisions. We assessed the available clinical data to aid practicing clinicians in their routine clinical decision-making. Clinical trials have demonstrated efficacy benefits for new therapies in advanced NETs. Emerging long-term data from these trials have enabled clinicians to make more accurate risk-benefit assessments, particularly for patients receiving multiple lines of therapy. However, clinical data specifically regarding treatment sequencing are limited. In lieu of definitive data, treatment sequencing should be based on disease-related factors (e.g., site of tumor origin, volume of disease) and patient-related characteristics (e.g., comorbidities, patient preferences). Clinical decision-making in advanced NETs remains highly individualized and complex; important evidence gaps regarding treatment sequencing remain. Given this, advanced NET management should be a joint effort of multidisciplinary teams at referring and high-volume centers. Additional clinical trial and real-world evidence are needed to meet the challenge of understanding how to sequence available NET therapies. Until these trials are conducted, the best practices provided in this review may serve as a guide for clinicians making treatment sequencing decisions based on the available data.

Key Factors to Attract More U.S. Diagnostic Radiology Residents into the Field of Nuclear Medicine and Molecular Imaging: A National Survey

RATIONALE AND OBJECTIVES

To understand the current state of radiology residents' exposure to nuclear medicine and molecular imaging (NM/MI), determine key factors that may attract more trainees into the field, and identify differentiating aspects between those specializing in NM/MI and those who are not.

MATERIALS AND METHODS

An anonymous web-based survey was sent to contacts at all diagnostic radiology residency programs in the United States for dissemination to their residents, collecting information about trainees' NM/MI exposure during residency and factors that may attract them to NM/MI.

RESULTS

A total of 198 trainees responded to the survey, 34 of whom plan on pursuing a career in NM/MI. Most trainees reported early exposure to NM/MI during residency; most (97.4%) reported ample exposure to general NM/MI and oncologic studies. Less than 3% of trainees reported adequate exposure to therapies, neurological applications, molecular imaging/research advances, and physics. Respondents reported a need for better quality education (38.9%) and exposure to mentors (28.8%) as ways to attract trainees to NM/MI. Routinely encountered clinical pathology was the most interesting for those specializing in NM/MI (29.4%), whereas lifestyle was the most attractive aspect of NM/MI for those not pursuing a career in the field (27.4%). NM/MI-associated research was the least attractive for those specializing in NM/MI (35.3%), while job market concerns was the least attractive aspect for those not specializing in NM/MI (37.2%). Trainees planning to specialize in NM/MI reported higher satisfaction with their orientation to NM/MI during their first clinical rotation compared to those who do not plan to specialize in the field (3.03/5.00 and 2.67/5.00, respectively, p = 0.04).

CONCLUSION

This survey highlights several factors that training programs and national societies can target to improve interest in NM/MI among radiology residents. We found that optimized education initiatives, including improved orientation to the field, increased mentoring, and career opportunities are essential levers for recruiting radiology trainees into the NM/MI workforce.

Prognostic and Predictive Biomarkers for Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine tumors (PanNETs) represent a clinically challenging disease because these tumors vary in clinical presentation, natural history, and prognosis. Novel prognostic biomarkers are needed to improve patient stratification and treatment options. Several putative prognostic and/or predictive biomarkers (eg, alternative lengthening of telomeres, alpha-thalassemia/mental retardation, X-linked (ATRX)/Death Domain Associated Protein (DAXX) loss) have been independently validated. Additionally, recent transcriptomic and epigenetic studies focusing on endocrine differentiation have identified PanNET subtypes that display similarities to either α-cells or β-cells and differ in clinical outcomes. Thus, future prospective studies that incorporate genomic and epigenetic biomarkers are warranted and have translational potential for individualized therapeutic and surveillance strategies.

Systemic Therapy of Advanced Well-differentiated Small Bowel Neuroendocrine Tumors Progressive on Somatostatin Analogues

OPINION STATEMENT

Neuroendocrine neoplasms (NENs) are a heterogeneous group of tumors whose management requires a nuanced and multi-disciplinary approach in order to control symptoms, halt tumor growth, and improve survival outcomes. Of late, the treatment landscape of NENs has advanced considerably as a result of several pivotal clinical trials, which have established somatostatin analogues as first-line therapy for advanced, metastatic, well-differentiated neuroendocrine tumors (NETs). However, an evolving classification system as well as an increased understanding of distinct clinical, molecular, and biologic features contribute to complexity in management. In particular, there remains limited randomized prospective data in the somatostatin analogue (SSA)-refractory setting for patients with primary tumors that originate in the small bowel. For well-differentiated small bowel neuroendocrine tumors (SBNETs), treatment beyond SSAs includes radionuclide therapy, targeted agents, liver-directed therapy, and to a lesser extent, cytotoxic chemotherapy. In the current era, selection of these agents is largely based on expert opinion in the context of patient and tumor characteristics without definitive data on the preferred order of agents to administer. In this review, we aim to describe the treatment landscape of metastatic SBNETs beyond SSAs and provide an overview of novel treatments which are currently under clinical evaluation.

Comparison of Choi, RECIST and Somatostatin Receptor PET/CT Based Criteria for the Evaluation of Response and Response Prediction to PRRT

Aim: The most suitable method for assessment of response to peptide receptor radionuclide therapy (PRRT) of neuroendocrine tumors (NET) is still under debate. In this study we aimed to compare size (RECIST 1.1), density (Choi), Standardized Uptake Value (SUV) and a newly defined ZP combined parameter derived from Somatostatin Receptor (SSR) PET/CT for prediction of both response to PRRT and overall survival (OS). Material and Methods: Thirty-four NET patients with progressive disease (F:M 23:11; mean age 61.2 y; SD ± 12) treated with PRRT using either Lu-177 DOTATOC or Lu-177 DOTATATE and imaged with Ga-68 SSR PET/CT approximately 10–12 weeks prior to and after each treatment cycle were retrospectively analyzed. Median duration of follow-up after the first cycle was 63.9 months (range 6.2–86.2). A total of 77 lesions (2–8 per patient) were analyzed. Response assessment was performed according to RECIST 1.1, Choi and modified EORTC (MORE) criteria. In addition, a new parameter named ZP, the product of Hounsfield unit (HU) and SUVmean (Standard Uptake Value) of a tumor lesion, was tested. Further, SUV values (max and mean) of the tumor were normalized to SUV of normal liver parenchyma. Tumor response was defined as CR, PR, or SD. Gold standard for comparison of baseline parameters for prediction of response of individual target lesions to PRRT was change in size of lesions according to RECIST 1.1. For prediction of overall survival, the response after the first and second PRRT were tested. Results: Based on RECIST 1.1, Choi, MORE, and ZP, 85.3%, 64.7%, 61.8%, and 70.6% achieved a response whereas 14.7%, 35.3%, 38.2%, and 29.4% demonstrated PD (progressive disease), respectively. Baseline ZP and ZPnormalized were found to be the only parameters predictive of lesion progression after three PRRT cycles (AUC ZP 0.753; 95% CI 0.6–0.9, p 0.037; AUC ZPnormalized 0.766; 95% CI 0.6–0.9; p 0.029). Based on a cut-off-value of 1201, ZP achieved a sensitivity of 86% and a specificity of 67%, while ZPnormalized reached a sensitivity of 86% and a specificity of 76% at a cut-off-value of 198. Median OS in the total cohort was not reached. In univariate analysis amongst all parameters, only patients having progressive disease according to MORE after the second cycle of PRRT were found to have significantly shorter overall survival (median OS in objective responders not reached, in PD 29.2 months; p 0.015). Patients progressive after two cycles of PRRT according to ZP had shorter OS compared to those responding (median OS for responders not reached, for PD 47.2 months, p 0.066). Conclusions: In this explorative study, we showed that Choi, RECIST 1.1, and SUVmax-based response evaluation varied significantly from each other. Only patients showing progressive disease after two PRRT cycles according to MORE criteria had a worse prognosis while baseline ZP and ZPnormalized performed best in predicting lesion progression after three cycles of PRRT.

Advances in medical treatment for pancreatic neuroendocrine neoplasms

Pancreatic neuroendocrine neoplasms (PanNENs) are rare neoplasms with strong heterogeneity that have experienced an increasing incidence rate in recent years. For patients with locally advanced or distant metastatic PanNENs, systemic treatment options vary due to the different differentiations, grades and stages. The available options for systemic therapy include somatostatin analogs, mole-cularly targeted agents, cytotoxic chemotherapeutic agents, immune checkpoint inhibitors, and peptide receptor radionuclide therapy. In addition, the development of novel molecularly targeted agents is currently in progress. The sequence of selection between different chemotherapy regimens has been of great interest, and resistance to chemotherapeutic agents is the major limitation in their clinical application. Novel agents and high-level clinical evidence continue to emerge in the field of antiangiogenic agents. Peptide receptor radionuclide therapy is increasingly employed for the treatment of advanced neuroendocrine tumors, and greater therapeutic efficacy may be achieved by emerging radio-labeled peptides. Since immune checkpoint inhibitor monotherapies for PanNENs appear to have limited antitumor activity, dual immune checkpoint inhibitor therapies or combinations of antiangiogenic therapies and immune checkpoint inhibitors have been applied in the clinic to improve clinical efficacy. Combining the use of a variety of agents with different mechanisms of action provides new possibilities for clinical treatments. In the future, the study of systemic therapies will continue to focus on the screening of the optimal benefit population and the selection of the best treatment sequence strategy with the aim of truly achieving individualized precise treatment of PanNENs.

In patients with well-differentiated neuroendocrine tumours, there is no apparent benefit of somatostatin analogues after disease control by peptide receptor radionuclide therapy

PURPOSE

Peptide receptor radionuclide therapy (PRRT) and somatostatin analogues (SSAs) are commonly combined as primary treatment for neuroendocrine neoplasms (NEN), and SSAs given as maintenance. We sought to evaluate whether sequential therapy with PRRT followed by SSAs has progression or survival benefits in patients with NEN after disease control by PRRT.

METHODS

This prospective, randomised, single-centre study had as principal eligibility criteria: unresectable, locally advanced, or metastatic, histologically confirmed well-differentiated NEN; no symptoms/biochemical diagnosis of carcinoid syndrome; no SSAs or ≤ 3 months of SSAs before PRRT; and stable disease or partial or complete response after PRRT. Altogether, 115 patients were randomised 2:1 to an SSA group (n = 74) given octreotide acetate LAR every 4 weeks, or a control group (n = 41) receiving only best supportive care. Octreotide treatment was to stop upon intolerable toxicity or patient refusal, or, at physician/patient discretion, upon NEN progression. The primary endpoint was progression-free survival (PFS), the secondary endpoint, and overall survival (OS).

RESULTS

Median (25th-75th percentile) follow-up from the first PRRT activity to death or latest observation was 6.6 (3.18-10.22) years. During that time, 71/115 patients (62%) progressed, 52/74 (70%) in the SSA group, and 19/41 (46%) in the control group (p = 0.01). Eighty-eight/115 patients (76%) died, 58/74 (78%) in the SSA group, and 30/41 (73%) in the control group (p = 0.52). Median (95% CI) PFS was 4.7 (2.8-7.7) years in the SSA group, and 6.4 (4.1-not reached) years in controls. Overall, median OS was 6.6 years. Neither PFS nor OS differed between groups (p = 0.129, p = 0.985, respectively).

CONCLUSIONS

In patients with disease control after PRRT, subsequent SSA treatment appeared not to be associated with better PFS or OS. Whether to continue SSA administration upon progression after PRRT requires evaluation in a prospective, randomised, controlled multicentre study with a relatively homogeneous sample.

Medical management of gastrointestinal neuroendocrine tumors

PURPOSE OF REVIEW

To summarize the recent developments in the medical treatment of gastrointestinal neuroendocrine neoplasms.

RECENT FINDINGS

The medical management of gastrointestinal neuroendocrine tumors (GI-NETs) continues to evolve with advances in the management of symptoms related to hormone hypersecretion and therapeutic control of disease progression. Systemic therapy options include somatostatin analogs (SSAs), radiolabeled SSAs, molecularly targeted agents, and cytotoxic therapy. Recent progress has focused on new targeted therapies, the sequencing of therapy and the role of immunotherapy.

SUMMARY

This review will focus on treatment of GI-NETs and highlight new developments published over the last year.

Orchestrating Treatment Modalities in Metastatic Pancreatic Neuroendocrine Tumors-Need for a Conductor

Simple Summary

Pancreatic neuroendocrine tumors (pNET) are a heterogeneous and challenging entity, and today’s guidelines offer a variety of treatment modalities, while surgery has a clear role for patients with resectable tumors and early stages, advanced, or metastatic pNET may benefit from treatments that were evaluated in randomized controlled studies during the last year. With this review, we aim to provide an updated view on treatment options for metastatic pNET.

Abstract

Pancreatic neuroendocrine tumors (pNETs) are a vast growing disease. Over 50% of these tumors are recognized at advanced stages with lymph node, liver, or distant metastasis. An ongoing controversy is the role of surgery in the metastatic setting as dedicated systemic treatments have emerged recently and shown benefits in randomized trials. Today, liver surgery is an option for advanced pNETs if the tumor has a favorable prognosis, reflected by a low to moderate proliferation index (G1 and G2). Surgery in this well-selected population may prolong progression-free and overall survival. Optimal selection of a treatment plan for an individual patient should be considered in a multidisciplinary tumor board. However, while current guidelines offer a variety of modalities, there is so far only a limited focus on the right timing. Available data is based on small case series or retrospective analyses. The focus of this review is to highlight the right time-point for surgery in the setting of the multimodal treatment of an advanced pancreatic neuroendocrine tumor.

Peptide receptor radionuclide therapy implementation and results in a predominantly gastrointestinal neuroendocrine tumor population: A two-year experience in a nonuniversity setting

Neuroendocrine tumors (NETs) are rare, but the incidence and prevalence of NETs are increasing in the United States. While surgery is the preferred treatment for NETs, it is not a viable option for metastatic disease. Lutathera (177Lu-DOTATATE) is approved by the United States Food and Drug Administration and the European Medicines Agency for the treatment of gastroenteropancreatic (GEP)-NETs in adults. There is limited information on GEP-NET treatment responses to Lutathera.Our institution launched a peptide receptor radionuclide therapy (PRRT) service line using Lutathera with involvement from a multidisciplinary team and complete collaboration between hospital administration and clinical providers. A prospective registry study was also established in order to collect patient demographics and clinical data regarding the treatment of GEP primary NETs with Lutathera.Between August 2018 and July 2020, 35 GEP-NET patients were treated with Lutathera, of which 65.71% received 4 complete cycles and 25.71% received 3 cycles; 5.71% and 2.86% received 2 and 1 cycles of PRRT, respectively. Most adverse events during the course of our study were low grade using the common terminology criteria for adverse events system. Of the patients who completed all 4 cycles: 22% showed partial response to Lutathera, 44% showed stable disease, and 13% showed disease progression based on a qualitative assessment of positron emission tomography/computed tomography imaging.From our experience, Lutathera was well tolerated in patients with GEP-NET. Additional studies are needed to examine long-term clinical and patient-reported outcomes associated with GEP-NET treatment as well as financial considerations for hospitals embarking on a PRRT program.

Radiolabeled Somatostatin Analogues for Diagnosis and Treatment of Neuroendocrine Tumors

Simple Summary

Neuroendocrine neoplasms (NENs) are rare and heterogeneous tumors, presenting in often challenging clinical scenarios, and require multidisciplinary discussion for optimal care. The theranostic approach (DOTA peptides labelled with ⁶⁸Ga for imaging well-differentiated neuroendocrine tumors NETs, and labelled with ⁹⁰Y or ¹⁷⁷Lu for therapy) plays a crucial role in the management of NENs to assess disease extension and criteria for peptide receptor radionuclide therapy (PRRT) eligibility of based on somatostatin receptor (SSTR) expression. The present paper is an overview of currently employed radiolabeled SSTR analogues used for both diagnosis and therapy of NENs. Further emerging radiopharmaceuticals targeting SSTRs (e.g., fluorinated SSTR agonists, radiolabeled SSTR antagonists) as well as strategies to improve PRRT efficacy (by means of implementation of personalized treatment schemes, dosimetry, amelioration of response assessment strategies, and optimization of treatment sequencing) are also discussed. Finally, although very preliminary, some studies employing radiomic features in various kinds of NET are reported.

Abstract

Neuroendocrine neoplasms (NENs) are rare and heterogeneous tumors that require multidisciplinary discussion for optimal care. The theranostic approach (DOTA peptides labelled with ⁶⁸Ga for diagnosis and with ⁹⁰Y or ¹⁷⁷Lu for therapy) plays a crucial role in the management of NENs to assess disease extension and as a criteria for peptide receptor radionuclide therapy (PRRT) eligibility based on somatostatin receptor (SSTR) expression. On the diagnostic side, [⁶⁸Ga]Ga-DOTA peptides PET/CT (SSTR PET/CT) is the gold standard for imaging well-differentiated SSTR-expressing neuroendocrine tumors (NETs). [¹⁸F]FDG PET/CT is useful in higher grade NENs (NET G2 with Ki-67 > 10% and NET G3; NEC) for more accurate disease characterization and prognostication. Promising emerging radiopharmaceuticals include somatostatin analogues labelled with ¹⁸F (to overcome the limits imposed by ⁶⁸Ga), and SSTR antagonists (for both diagnosis and therapy). On the therapeutic side, the evidence gathered over the past two decades indicates that PRRT is to be considered as an effective and safe treatment option for SSTR-expressing NETs, and is currently included in the therapeutic algorithms of the main scientific societies. The positioning of PRRT in the treatment sequence, as well as treatment personalization (e.g., tailored dosimetry, re-treatment, selection criteria, and combination with other alternative treatment options), is warranted in order to improve its efficacy while reducing toxicity. Although very preliminary (being mostly hampered by lack of methodological standardization, especially regarding feature selection/extraction) and often including small patient cohorts, radiomic studies in NETs are also presented. To date, the implementation of radiomics in clinical practice is still unclear. The purpose of this review is to offer an overview of radiolabeled SSTR analogues for theranostic use in NENs.

Treatment of Neuroendocrine Neoplasms with Radiolabeled Peptides-Where Are We Now

Peptide receptor radionuclide therapy (PRRT) has been one of the most successful and exciting examples of theranostics in nuclear medicine in recent decades and is now firmly embedded in many treatment algorithms for unresectable or metastatic neuroendocrine neoplasms (NENs) worldwide. It is widely considered to be an effective treatment for well- or moderately differentiated neoplasms, which express high levels of somatostatin receptors that can be selectively targeted. This review article outlines the scientific basis of PRRT in treatment of NENs and describes its discovery dating back to the early 1990s. Early treatments utilizing Indium-111, a γ-emitter, showed promise in reduction in tumor size and improvement in biochemistry, but were also met with high radiation doses and myelotoxic and nephrotoxic effects. Subsequently, stable conjugation of DOTA-peptides with β-emitting radionuclides, such as Yttrium-90 and Lutetium-177, served as a breakthrough for PRRT and studies highlighted their potential in eliciting progression-free survival and quality of life benefits. This article will also elaborate on the key trials which paved the way for its approval and will discuss therapeutic considerations, such as patient selection and administration technique, to optimize its use.

Association of Upfront Peptide Receptor Radionuclide Therapy With Progression-Free Survival Among Patients With Enteropancreatic Neuroendocrine Tumors

IMPORTANCE

Data about the optimal timing for the initiation of peptide receptor radionuclide therapy (PRRT) for advanced, well-differentiated enteropancreatic neuroendocrine tumors are lacking.

OBJECTIVE

To evaluate the association of upfront PRRT vs upfront chemotherapy or targeted therapy with progression-free survival (PFS) among patients with advanced enteropancreatic neuroendocrine tumors who experienced disease progression after treatment with somatostatin analogues (SSAs).

DESIGN, SETTING, AND PARTICIPANTS

This retrospective, multicenter cohort study analyzed the clinical records from 25 Italian oncology centers for patients aged 18 years or older who had unresectable, locally advanced or metastatic, well-differentiated, grades 1 to 3 enteropancreatic neuroendocrine tumors and received either PRRT or chemotherapy or targeted therapy after experiencing disease progression after treatment with SSAs between January 24, 2000, and July 1, 2020. Propensity score matching was done to minimize the selection bias.

EXPOSURES

Upfront PRRT or upfront chemotherapy or targeted therapy.

MAIN OUTCOMES AND MEASURES

The main outcome was the difference in PFS among patients who received upfront PRRT vs among those who received upfront chemotherapy or targeted therapy. A secondary outcome was the difference in overall survival between these groups. Hazard ratios (HRs) were fitted in a multivariable Cox proportional hazards regression model to adjust for relevant factors associated with PFS and were corrected for interaction with these factors.

RESULTS

Of 508 evaluated patients (mean ([SD] age, 55.7 [0.5] years; 278 [54.7%] were male), 329 (64.8%) received upfront PRRT and 179 (35.2%) received upfront chemotherapy or targeted therapy. The matched group included 222 patients (124 [55.9%] male; mean [SD] age, 56.1 [0.8] years), with 111 in each treatment group. Median PFS was longer in the PRRT group than in the chemotherapy or targeted therapy group in the unmatched (2.5 years [95% CI, 2.3-3.0 years] vs 0.7 years [95% CI, 0.5-1.0 years]; HR, 0.35 [95% CI, 0.28-0.44; P < .001]) and matched (2.2 years [95% CI, 1.8-2.8 years] vs 0.6 years [95% CI, 0.4-1.0 years]; HR, 0.37 [95% CI, 0.27-0.51; P < .001]) populations. No significant differences were shown in median overall survival between the PRRT and chemotherapy or targeted therapy groups in the unmatched (12.0 years [95% CI, 10.7-14.1 years] vs 11.6 years [95% CI, 9.1-13.4 years]; HR, 0.81 [95% CI, 0.62-1.06; P = .11]) and matched (12.2 years [95% CI, 9.1-14.2 years] vs 11.5 years [95% CI, 9.2-17.9 years]; HR, 0.83 [95% CI, 0.56-1.24; P = .36]) populations. The use of upfront PRRT was independently associated with improved PFS (HR, 0.37; 95% CI, 0.26-0.51; P < .001) in multivariable analysis. After adjustment of values for interaction, upfront PRRT was associated with longer PFS regardless of tumor functional status (functioning: adjusted HR [aHR], 0.39 [95% CI, 0.27-0.57]; nonfunctioning: aHR, 0.29 [95% CI, 0.16-0.56]), grade of 1 to 2 (grade 1: aHR, 0.21 [95% CI, 0.12-0.34]; grade 2: aHR, 0.52 [95% CI, 0.29-0.73]), and site of tumor origin (pancreatic: aHR, 0.41 [95% CI, 0.24-0.61]; intestinal: aHR, 0.19 [95% CI, 0.11-0.43]) (P < .001 for all). Conversely, the advantage was not retained in grade 3 tumors (aHR, 0.31; 95% CI, 0.12-1.37; P = .13) or in tumors with a Ki-67 proliferation index greater than 10% (aHR, 0.73; 95% CI, 0.29-1.43; P = .31).

CONCLUSIONS AND RELEVANCE

In this cohort study, treatment with upfront PRRT in patients with enteropancreatic neuroendocrine tumors who had experienced disease progression with SSA treatment was associated with significantly improved survival outcomes compared with upfront chemotherapy or targeted therapy. Further research is needed to investigate the correct strategy, timing, and optimal specific sequence of these therapeutic options.

Peptide Receptor Radionuclide Therapy Targeting the Somatostatin Receptor: Basic Principles, Clinical Applications and Optimization Strategies

Simple Summary

Peptide receptor radionuclide therapy (PRRT) is a systemic treatment consisting of the administration of a tumor-targeting radiopharmaceutical into the circulation of a patient. The radiopharmaceutical will bind to a specific peptide receptor leading to tumor-specific binding and retention. This will subsequently cause lethal DNA damage to the tumor cell. The only target that is currently used in widespread clinical practice is the somatostatin receptor, which is overexpressed on a range of tumor cells, including neuroendocrine tumors and neural-crest derived tumors. Academia played an important role in the development of PRRT, which has led to heterogeneous literature over the last two decades, as no standard radiopharmaceutical or regimen has been available for a long time. This review focuses on the basic principles and clinical applications of PRRT, and discusses several PRRT-optimization strategies.

Abstract

Peptide receptor radionuclide therapy (PRRT) consists of the administration of a tumor-targeting radiopharmaceutical into the circulation of a patient. The radiopharmaceutical will bind to a specific peptide receptor leading to tumor-specific binding and retention. The only target that is currently used in clinical practice is the somatostatin receptor (SSTR), which is overexpressed on a range of tumor cells, including neuroendocrine tumors and neural-crest derived tumors. Academia played an important role in the development of PRRT, which has led to heterogeneous literature over the last two decades, as no standard radiopharmaceutical or regimen has been available for a long time. This review provides a summary of the treatment efficacy (e.g., response rates and symptom-relief), impact on patient outcome and toxicity profile of PRRT performed with different generations of SSTR-targeting radiopharmaceuticals, including the landmark randomized-controlled trial NETTER-1. In addition, multiple optimization strategies for PRRT are discussed, i.e., the dose–effect concept, dosimetry, combination therapies (i.e., tandem/duo PRRT, chemoPRRT, targeted molecular therapy, somatostatin analogues and radiosensitizers), new radiopharmaceuticals (i.e., SSTR-antagonists, Evans-blue containing vector molecules and alpha-emitters), administration route (intra-arterial versus intravenous) and response prediction via molecular testing or imaging. The evolution and continuous refinement of PRRT resulted in many lessons for the future development of radionuclide therapy aimed at other targets and tumor types.

[177Lu]Lu-DOTA-TATE versus standard of care in adult patients with gastro-enteropancreatic neuroendocrine tumours (GEP-NETs): a cost-consequence analysis from an Italian hospital perspective

Purpose

To assess and compare clinical outcomes and costs, to the Italian healthcare system, of three therapeutic options approved in the management of adult patients with gastro-enteropancreatic neuroendocrine tumours (GEP-NETs).

Methods

We compared the efficacy, safety, and costs of [177Lu]Lu-DOTA-TATE, everolimus (both originator and generic products), and sunitinib in patients with advanced GEP-NETs (NET G1 and G2) that had progressed following treatment with somatostatin analogs (SSAs). A cost-consequence model was developed and validated by a panel of clinical experts from three NET reference centres in Italy. The clinical outcomes included in the model were median progression-free survival and the incidence of grade 3 or 4 adverse events (AEs), as reported in pivotal clinical trials. The costs for acquisition and administration of each treatment, and of managing AEs, were calculated from the perspective of the Italian national health service. Treatment costs per progression-free month were calculated separately for patients with NETs of pancreatic (PanNETs; all three treatments) and gastrointestinal (GI-NETs; [177Lu]Lu-DOTA-TATE and everolimus only) origin.

Results

In patients with PanNETs, total costs per progression-free month were €2989 for [177Lu]Lu-DOTA-TATE, €4975 for originator everolimus, €3472 for generic everolimus, and €5337 for sunitinib. In patients with GI-NETs, total costs per progression-free month were €3189 for [177Lu]Lu-DOTA-TATE, €4990 for originator everolimus, and €3483 for generic everolimus.

Conclusions

[177Lu]Lu-DOTA-TATE was associated with lower costs per progression-free month versus relevant treatment options in patients with GI-NETs or PanNETs (NET G1–G2; progressed following SSA treatment), although acquisition and administration costs are higher. These findings provide further economic arguments in the overall context of treatment decision-making.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-021-05656-x.

Expanding Theranostic Radiopharmaceuticals for Tumor Diagnosis and Therapy

Radioligand theranostics (RT) in oncology use cancer-type specific biomarkers and molecular imaging (MI), including positron emission tomography (PET), single-photon emission computed tomography (SPECT) and planar scintigraphy, for patient diagnosis, therapy, and personalized management. While the definition of theranostics was initially restricted to a single compound allowing visualization and therapy simultaneously, the concept has been widened with the development of theranostic pairs and the combination of nuclear medicine with different types of cancer therapies. Here, we review the clinical applications of different theranostic radiopharmaceuticals in managing different tumor types (differentiated thyroid, neuroendocrine prostate, and breast cancer) that support the combination of innovative oncological therapies such as gene and cell-based therapies with RT.

Peptide receptor radionuclide therapy as a tool for the treatment of severe hypoglycemia in patients with primary inoperable insulinoma

Objectives

Severe hypoglycemia in a course of inoperable insulinoma may be life-threating and often it is not well controlled, even by high doses of diazoxide requiring second line treatment. Among available methods PRRT is characterized by relatively low toxicity and is connected with favorable antitumor effect. The aim of the study was an evaluation of the PRRT effectiveness in control of hypoglycemia in patients with primary inoperable insulinoma.

Methods

Three patients (female with metastatic insulinoma, male with primary inoperable pancreatic tumor, female with MEN1 syndrome and hepatic metastases) were treated with PRRT due to severe hypoglycemia poorly controlled by diazoxide in course of primary inoperable insulinoma.

Results

Patient 1 baseline fasting glucose concentration increased from 2.4 mmol/L [3.30–5.60] to 5.9 mmol/L after PRRT. In patient 2 fasting glucose level 2.30 mmol/L increased after PRRT to 7.0 mmol/L, while baseline insulin level initially 31.15 uU/mL [2.6–24.9] decreased to 15.4 uU/mL. In patients 3, baseline fasting glucose level 2.5 mmol/L increased after PRRT to 7.9 mmol/L, and insulin decreased from 57.9 uU/mL to 6.3 uU/mL. In imaging there was partial response (PR) in patient 1 and 2 and stabilization of the tumor size in patient 3. In patient 2 reduction of tumor infiltration let for curative surgery performed 4 months after PPRT.

Conclusions

PRRT may be effective as a first or second line treatment in management of hypoglycemia for patients with hormonally active inoperable insulinoma.

Making Sense of a Complex Disease: A Practical Approach to Managing Neuroendocrine Tumors

Neuroendocrine tumors (NETs) are a heterogeneous clinical entity with a broad range of grade, pace of disease, functional status, and primary sites. Pathologic classification, diagnostic modalities, and therapeutic options for NETs have evolved considerably in the past decade. In part driven by these advances, incidence and prevalence of NETs are rising in the United States and the practicing oncologist is likely to encounter these in the clinic. However, there are no clear lines of therapy for unresectable or metastatic NETs, and sequencing of systemic therapies depends on consideration of patient and tumor characteristics including extent of disease, grade, pace of growth, functional status, primary site, somatostatin receptor status, performance status, and comorbidities. Familiarity with ongoing clinical trials will guide therapeutic decision making as well. In this review, we seek to provide a framework to formulate and tailor an individualized treatment plan for each patient with a NET.

[Endocrine and neuroendocrine tumors]

Endokrine Tumoren und hier im Speziellen neuroendokrine Neoplasien des Gastrointestinaltraktes (GEP-NETs), Phäochromozytome (PCs), Paragangliome (PGL) und Schilddrüsentumoren sind Paradebeispiele für die Bedeutung von Molekularpathologie und Molekularbiologie für Diagnostik, Klassifikation und letztendlich auch die (chirurgische) Therapie dieser Erkrankungen. Bei GEP-NETs erfolgt das Grading anhand des Ki-67-Index. Dieser bestimmt die Art der molekularen Bildgebung (DOTA [1,4,7,10-Tetraazacyclododecan‑1,4,7,10-tetraessigsäure]/DOPA [3,4-Dihydroxyphenylalanin]/FDG[Fluordesoxyglukose]-PET[Positronenemissionstomographie]/CT [Computertomographie]), die mögliche Therapie (chirurgisch und/oder Radiopeptidtherapie), antiproliferative und symptomkontrollierende Therapie mit Somatostatinanaloga und letztendlich auch die Prognose. PC/PGL können hereditär auftreten (MEN2A [multiple endokrine Neoplasie Typ 2A], VHL [Von-Hippel-Lindau-Tumorsuppressor], NF1 [Neurofibromatose Typ 1], SDH[Succinat-Dehydrogenase]-Mutationen), was die chirurgische Therapie und die präoperative Medikation maßgeblich beeinflusst. Die molekulare Bildgebung hat einen hohen Stellenwert und kann bei grenzwertiger Biochemie wegweisend sein. Auch Nebennierenrindenkarzinome können genetisch determiniert sein. Bei Schilddrüsentumoren ist v. a. die Pathologie der C‑Zelle (C-Zell-Hyperplasie, medulläres Schilddrüsenkarzinom) hervorzuheben. Bei hereditärer Erkrankung (FMTC [familiäres medulläres Schilddrüsenkarzinom], MEN[multiple endokrine Neoplasie]2) ist häufig eine frühe prophylaktische Operation notwendig und verhindert das Auftreten von fortgeschrittenen Karzinomen. Aber auch die Bestimmung des Resektionsausmaßes bei follikulären Läsionen bzw. die Unterscheidung zwischen „non-invasive follicular thyroid neoplasm with papillary-like nuclear features“ (NIFTPs) und follikulären Varianten des papillären Schilddrüsenkarzinoms kann mithilfe spezifischer Marker erfolgen. Insgesamt hat die Molekularpathologie eine zunehmende Bedeutung bei diesen Entitäten und ist auch Inhalt laufender Forschungsprojekte.

Combination Therapies with PRRT

Peptide receptor radionuclide therapy (PRRT) is a successful targeted radionuclide therapy in neuroendocrine tumors (NETs). However, complete responses remain elusive. Combined treatments anticipate synergistic effects and thus better responses by combining ionizing radiation with other anti-tumor treatments. Furthermore, multimodal therapies often have a balanced toxicity profile. To date, few studies have evaluated the effect of combination therapies with PRRT, some of them phase I/II trials. This review will focus on several clinically tested, tailored approaches to improving the effects of PRRT. The aim is to help clinicians in the treatment planning of NETs to choose the most effective and safe treatment for each patient in the sense of personalized medicine. Current promising combination partners of PRRT are somatostatin analogues (SSAs), chemotherapy, molecular targeted treatment, liver radioembolization, and dual radionuclide PRRT (Lutetium-177-PRRT combined with Yttrium-90-PRRT).