Current Practices and Novel Techniques in the Diagnosis and Management of Neuroendocrine Tumors of Unknown Primary

Emerging Treatment Options for Neuroendocrine Neoplasms of Unknown Primary Origin: Current Evidence and Future Perspectives

Among neuroendocrine neoplasms (NENs), a non-negligible proportion (9-22%) is represented by sufferers of NENs of unknown primary origin (UPO), a poor prognostic group with largely unmet clinical needs. In the absence of standard therapeutic algorithms, current guidelines suggest that the treatment of UPO-NENs should be based on tumor clinical-pathological characteristics, disease burden, and patient conditions. Chemotherapy represents the backbone for the treatment of high-grade poorly differentiated UPO-NENs, usually providing deep but short-lasting responses. Conversely, the spectrum of available systemic therapy options for well-differentiated UPO-NENs may range from somatostatin analogs in indolent low-grade tumors, to peptide receptor radioligand therapy, tyrosine kinase inhibitors (TKIs), or chemotherapy for more aggressive tumors or in case of high disease burden. In recent years, molecular profiling has provided deep insights into the molecular landscape of UPO-NENs, with both diagnostic and therapeutic implications. Although preliminary, interesting activity data have been provided about upfront chemoimmunotherapy, the use of immune checkpoint inhibitors (ICIs), and the combination of ICIs plus TKIs in this setting. Here, we review the literature from the last 30 years to examine the available evidence about the treatment of UPO-NENs, with a particular focus on future perspectives, including the expanding scenario of targeted agents in this setting.

Neuroendocrine tumour of the lesser omentum

A man in his early 20s presented to us in the outpatient department with a history of diarrhoea for 4 months. Investigations revealed elevated serum chromogranin levels and an intensely avid lesion in the gastrohepatic ligament in Gallium DOTATATE positron emission tomography (PET). The tumour was excised laparoscopically, and no other lesions were seen. The patient improved clinically and had a normal serum chromogranin level postoperatively. He is currently much improved at the 1year follow-up. We did an extensive workup to look for a primary tumour. It was concluded that it was a de novo tumour arising from the lesser sac. The recommended investigations in case of neuroendocrine tumour (NET) with unknown primary include blood investigations to look for the functional status of the tumour, histopathological examination, including immunohistochemistry, and radiological imaging, which must include a Gallium DOTATATE PET. An isolated NET of the lesser sac has not been reported in the literature.

Diagnostic Approaches to Neuroendocrine Neoplasms of Unknown Primary Site

ABSTRACT

Neuroendocrine tumors (NETs) are relatively uncommon heterogeneous neoplasms arising from endocrine and neuronal origin cells showing highly variable clinical behavior. By the time these tumors are discovered, up to 14% of patients with histologically proven NETs have metastasis, with the liver as the most frequently affected organ. Sometimes, no known primary site can be identified via routine imaging. Neuroendocrine tumors of unknown origin carry a poorer prognosis (compared with metastatic NETs with a known primary site) because of a lack of tailored surgical intervention and appropriate medical therapy (eg, chemotherapy or targeted therapy). A multimethod approach is frequently used in the trial to accurately determine the primary site for NETs of unknown primary sites and may include clinical, laboratory, radiological, histopathological, and surgical data. New molecular techniques using the genomic approach to identify the molecular signature have shown promising results. Various imaging modalities include ultrasound, computed tomography (CT), dual-energy CT, magnetic resonance imaging, and functional and hybrid imaging (positron emission tomography/CT, positron emission tomography/magnetic resonance imaging); somatostatin receptor imaging with new tracers is frequently used in an attempt for localization of the primary site.

Primary Renal Well-Differentiated Neuroendocrine Tumors: Analyis of Six Cases from a Tertiary Care Center in North India with Review of Literature

Well-differentiated renal neuroendocrine tumors are rare tumors. As their biologic behavior is not fully known, there is a need to know more about these cases. We performed a retrospective chart review of all the cases diagnosed with renal neuroendocrine tumors from January 2016 to December 2020 (five years) in order to understand their clinical features, morphological characteristics and outcome. We included six cases with mean age of 46.2 years (4 males) in our study. All patients underwent radical nephrectomy. Histologically all showed tumor disposed in nests and trabeculae and majority of the tumors belonged to well-differentiated neuroendocrine tumor Grade 1 (WHO criteria of gastoroenteropancreatic neuroendocrine neoplasms). Lymph node metastasis was seen in two cases at the time of clinical presentation. All the tumors were diffusely positive for neuroendocrine tumor markers (synaptophysin, chromogranin, NSE, CD56). Follow-up data was available in all cases with an average follow-up of two years and neither has shown evidence of metastasis or relapse till last follow-up. Role of morphological patterns and immunohistochemical markers is highlighted with the importance of including Ki-67 index in grading them to better understand their outcome.

Trends in incidence and survival in patients with gastrointestinal neuroendocrine tumors: A SEER database analysis, 1977-2016

Objectives

We aimed to determine trends in incidence and survival in patients with gastrointestinal neuroendocrine tumors (GI-NETs) from 1977 to 2016, and then analyze the potential risk factors including sex, age, race, grade, Socioeconomic status (SES), site, and stage.

Methods

Data were obtained from Surveillance, Epidemiology, and End Results Program (SEER) database. Kaplan-Meier survival analysis, relative survival rates (RSRs), and Cox proportional risk regression model were used to evaluate the relationship between these factors and prognosis.

Results

Compared with other sites, the small intestine and rectum have the highest incidence, and the appendix and rectum had the highest survival rate. The incidence was higher in males than in females, and the survival rate in males was close to females. Blacks had a higher incidence rate than whites, but similar survival rates. Incidence and survival rates were lower for G3&4 than for G1 and G2. Age, stage, and grade are risk factors.

Conclusions

This study described changes in the incidence and survival rates of GI-NETs from 1977 to 2016 and performed risk factor analyses related to GI-NETs.

An abdominal wall neuroendocrine tumor of unknown primary origin: A case report and review of the literature

Background

Neuroendocrine tumors (NETs) are neoplasms that arise from cells of the endocrine and nervous system. NETs, often found in the gastrointestinal tract, can be found anywhere in the body, and have metastatic potential. NETs occasionally present with metastatic disease without an identifiable primary tumor.

Case

A 79‐year‐old female patient presented with an abdominal wall mass. Percutaneous biopsy was consistent with a NET. Preoperative endoscopy and PillCam were unremarkable. PET Dotatate demonstrated uptake in the abdominal wall as well as vague uptake in the pelvis. Intraoperatively, we identified a suspicious nodule on the sigmoid colon, which was consistent with a drop metastasis on final pathology.

Conclusion

In this case report we present a patient with a NET metastasis to the abdominal wall without a known primary site. This case highlights the limitations of endoscopy and imaging in the workup of metastatic NETs. Additionally, this is a novel case report of a metastatic NET to the abdominal wall without an identifiable primary site.

Incidence, prevalence, and survival trends for neuroendocrine neoplasms in Victoria, Australia, from 1982 to 2019: Based on site, grade, and region

AIMS

Neuroendorcine neoplasms (NENs) are rare tumors characterised by variable biology and delayed diagnosis. Several population studies have reported a marked increased incidence over time. The objectives of this analysis were to describe within Victoria (the second largest Australian state, 6.4 Million) the trends for NENs incidence/survival over nearly 38 years (1982-2019), and regional differences in survival.

METHODS

All NEN cases were identified from the Victorian Cancer Registry over four time periods: 1982-1989, 1990-1999, 2000-2009, and 2010-2019. Data collected included primary tumor site, histological grade, gender, overall survival (OS), and place of residence. Incidence data were analyzed with the generation of annual standardized rates (ASR). OS was assessed for the entire cohort and between geographical regions.

RESULTS

The overall NEN population (1982-2019) included 8,106 patients: over 60% grade 1/2 NENs, especially small bowel and colorectal. The number of new diagnoses increased over three-fold over time for the overall cohort and by tumoral categories. The ASR increased similarly, especially pancreatic NENs (4.3-fold) and differed between genders. The 5-year OS rates and median OS increased over time for the overall cohort: from 52% to 67% (p < 0.001). OS was greater for NEN patients residing in major cities relative to regional/remote areas (p = 0.01).

CONCLUSION

This population-wide analysis with over 38 years of data has confirmed the international trends of the increased incidence, prevalence, and OS of NEN patients regardless of primary site or histological grade. The analysis also observed a difference in survival outcome in rural/remote versus urban areas.

The new WHO classification of gastrointestinal neuroendocrine tumors and immunohistochemical expression of somatostatin receptor 2 and 5

The 2019 World Health Organization (WHO) classification of gastrointestinal tumors defines well-differentiated grade 3 neuroendocrine tumors, the mixed neuroendocrine-non-neuroendocrine tumors (MiNENs) and classifies goblet cell carcinoid as goblet cell adenocarcinoma. The expression of somatostatin receptors (SSTRs) is the foundation for somatostatin analogue therapy. At present, there are only a few studies that have analyzed the immunohistochemical reactivity of SSTRs in gastrointestinal neuroendocrine neoplasms (NENs). The aim of the present study was to evaluate the immunohistochemical expression of SSTR2 and SSTR5 in gastrointestinal NENs and goblet cell adenocarcinomas and the correlation of these markers with clinical and morphological factors. The study included 67 patients with NENs and 4 patients with adenocarcinoma ex-goblet cell carcinoid diagnosed between January 2008 and December 2018. Tumors were reclassified according to the 2019 WHO classification. Immunohistochemical staining for chromogranin A, synaptophysin, Ki-67, p53, SSTR2, and SSTR5 were performed in all the cases. The results showed that, G1 and G2 neuroendocrine tumors were more common SSTR2-positive in comparison with G3 carcinomas (P<0.0001). In addition, 33.3% of neuroendocrine carcinomas and 2 cases of low-grade adenocarcinoma ex-goblet cell carcinoid were SSTR2-positive. Neuroendocrine carcinomas had significantly lower SSTR2 and SSTR5 expression compared with well-differentiated neuroendocrine tumors (P=0.0130; P=0.0437, respectively). The SSTR2 expression in the early tumor stages was 100%, more often than in advanced stages (55.6%; P=0.0011). The results demonstrated the decrease in SSTR2 expression with increasing malignancy and tumor stage. The SSTR2-positive expression in neuroendocrine carcinomas and adenocarcinoma ex-goblet cell carcinoid provides evidence for the benefits of somatostatin analog treatment associated with surgery and chemotherapy.

Clinical value of 68Ga-DOTA-SSTR PET/CT in the diagnosis and detection of neuroendocrine tumors of unknown primary origin: a systematic review and meta-analysis

BACKGROUND

The ability of ⁶⁸Ga-DOTA-SSTR to detect the primary sites of neuroendocrine tumors (NETs) remains undetermined, and the clinical benefit of this imaging agent is not clear.

PURPOSE

To evaluate the diagnostic accuracy of ⁶⁸Ga-DOTA-SSTR for carcinoma unknown primary (CUP) neuroendocrine tumors and to further analyze the detection rate of ⁶⁸Ga-DOTA-SSTR for primary and metastatic sites.

MATERIAL AND METHODS

A comprehensive literature search of PubMed/MEDLINE and ScienceDirect was performed in October 2019 in accordance with the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) guidelines. We critically reviewed all studies based on the PICOS criteria. QUADAS-2 was used to evaluate the quality of the methodology of the included studies.

RESULTS

A total of 10 studies (484 patients, mean age = 56.6 ± 4.3 years) were included in the study. The pooled sensitivity and specificity of ⁶⁸Ga-DOTA-SSTR in identifying CUP-NETs were 82% and 55%, respectively. The area under the receiver operating characteristic curve was 69%. Regarding metastasis sites, ⁶⁸Ga-DOTA-SSTR found the most metastases in the liver (57.9%), followed by the lymph nodes (22.8%), bones (12.8%), lung (2.8%), and others (1.7%). The pooled detection rate of ⁶⁸Ga-DOTA-SSTR for CUP-NETs was 61%.

CONCLUSION

The present study demonstrated the high diagnostic sensitivity of ⁶⁸Ga-DOTA-SSTR for CUP-NETs. ⁶⁸Ga-DOTA-SSTR PET/CT was highly effective in locating the primary and metastatic sites of CUP-NETs.

Cancers Metastatic to the Liver

The liver is a common site of metastatic cancer spread, and metastatic lesions are the most common malignant liver tumors. Diagnosis of liver metastases often is established based on clinical assessment, laboratory tests, and appropriate imaging. Surgical resection is the treatment of choice for resectable colorectal and neuroendocrine liver metastases. Long-term survival outcome data after treatment of hepatic metastases of noncolorectal non-neuroendocrine tumors are less robust. The treatment strategy for patients with liver metastases should be determined case by case in a multidisciplinary setting.