Long-acting octreotide treatment has no impact on tumor uptake of 99mTc-HYNIC-TOC in patients with neuroendocrine tumors

Quantitative uptake in 99m Tc-EDDA/HYNIC-TOC somatostatin receptor imaging - the effect of long-acting release somatostatin analogue therapy

PURPOSE

Withdrawal of long-acting release somatostatin analogue (LAR-SSA) treatment before somatostatin receptor imaging is based on empirical reasoning that it may block uptake at receptor sites. This study aims to quantify differences in uptake of 99m Tc-EDDA/HYNIC-TOC between patients receiving LAR-SSA and those who were not.

METHODS

Quantification of 177 patients (55 on LAR-SSA) imaged with 99m Tc-EDDA/HYNIC-TOC was performed, with analysis of pathological tissue and organs with physiological uptake using thresholded volumes of interest. Standardised uptake values (SUVs) and tumour/background (T/B) ratios were calculated and compared between the two patient groups.

RESULTS

SUVs were significantly lower for physiological organ uptake for patients on LAR-SSA (e.g. spleen: SUV max 13.3 ± 5.9 versus 33.9 ± 9.0, P  < 0.001); there was no significant difference for sites of pathological uptake (e.g. nodal metastases: SUV max 19.2 ± 13.0 versus 17.4 ± 11.5, P  = 0.552) apart from bone metastases (SUV max 14.1 ± 13.5 versus 7.7 ± 8.0, P  = 0.017) where it was significantly higher.

CONCLUSION

LAR-SSA has an effect only on physiological organ uptake of 99m Tc-EDDA/HYNIC-TOC, reducing uptake. It has no significant effect on pathological uptake for most sites of primary and metastatic disease. This should be taken into account if making quantitative measurements, calculating T/B ratios or assigning Krenning Scores. There is the potential for improved dosimetric results in Peptide Receptor Radionuclide Therapy by maintaining patients on LAR-SSA.

Multimodality imaging differentiation of pancreatic neuroendocrine tumors and solid pseudopapillary tumors with a nomogram model: A large single-center study

Background

Pancreatic neuroendocrine tumors (pNETs) and solid pseudopapillary tumors (SPTs) are two of the most common pancreatic neoplasms with different treatment procedures. However, the broad heterogeneity of pNETs and SPTs in clinical manifestations and radiological features often confuse the presurgical discrimination in clinical practice, and the clinical and molecular differentiation of the two tumors remains elusive to date. We presume that a large and comprehensive study into the multimodality features of pNETs and SPTs is necessary for precise clinical management.

Methods

We collected and analyzed the clinicopathological information and multimodality features of nonfunctional pNET and SPT patients, for a total of 631 cases from 2006 to 2021. Univariate analysis of imaging features, including contrast-enhanced computed tomography (CT), magnetic resonance imaging, endoscopic ultrasound (EUS) and nuclear medicine imaging, and clinical characteristics was performed, and CT features and clinical information were integrated to establish a nomogram model.

Results

We recruited 354 nonfunctional pNET and 277 SPT patients in our cohort. Regarding demographic information, pNET patients had a lower female percentage (55.4% vs. 72.9%), smaller tumor size (2.8 vs. 4.8 cm), and older age (53.4 vs. 35.3 years). In CT imaging and EUS, pNETs tended to appear as solid and homogenous lesions with strong enhancement intensity. Multifocal lesions, duct dilation, and lymph node (LN) enlargement were more likely to be observed in pNETs, while calcification was more common in SPT lesions. On positron emission tomography (PET)/CT, pNETs exhibited significant sensitivity to somatostatin receptor scintigraphy (SRS), with positive rates of 81.4% and 95% on ⁹⁹mTc-HYNIC-TOC and ⁶⁸Ga-DOTATATE PET/CT, respectively, while SPTs were all negative on SRS. Multivariate analysis identifies tumor size, age, enhancement intensity, calcification, and LN enlargement as statistically significant variables.

Conclusions

Compared to SPT patients, pNET patients exhibit an older age and smaller tumor size. CT manifestations of strong intensity, LN enlargement, and no calcification could indicate a higher possibility of pNET. Meanwhile, the similarity in the immunohistochemical profile indicates that the two tumors could potentially develop from the same origin.

Knowns and unknowns of bone metastases in patients with neuroendocrine neoplasms: A systematic review and meta-analysis

OBJECTIVE

This systematic review and meta-analysis aimed to develop an evidence-based summary of current knowledge of bone metastases (BMs) in neuroendocrine neoplasms (NENs), inform diagnosis and treatment and standardise management between institutions.

METHODS

PubMed, Medline, EMBASE and meeting proceedings were searched for eligible studies reporting data on patients with BMs and NENs of any grade of differentiation and site; poorly-differentiated large/small cell lung cancer were excluded. Data were extracted and analysed using STATA v.12. Meta-analysis of proportions for calculation of estimated pooled prevalence of BM and calculation of weighted pooled frequency and weighted pooled mean for other variables of interest was performed .

RESULTS

A total of 149 studies met the eligibility criteria. Pooled prevalence of BMs was 18.4% (95% CI 15.4-21.5). BMs were mainly metachronous with initial diagnosis of NEN (61.2%) and predominantly osteoblastic; around 61% were multifocal, with a predisposition in axial skeleton. PET/CT seemed to provide (together with MRI) the highest sensitivity and specificity for BM detection. Almost half of patients (46.4%) reported BM-related symptoms: pain (66%) and skeletal-related events (SREs, fracture/spinal cord compression) (26.2%; weightedweighted mean time-to-SRE 9.9 months). Management of BMs was multimodal [bisphosphonates and bone-modifying agents (45.2%), external beam radiotherapy (34.9%), surgery (14.8%)] and supported by little evidence. Overall survival (OS) from the time of diagnosis of BMs was long [weighted mean 50.9 months (95% CI 40.0-61.9)]. Patients with BMs had shorter OS [48.8 months (95% CI 37.9-59.6)] compared to patients without BMs [87.4 months (95% CI 74.9-100.0); p = 0.001]. Poor performance status and BM-related symptoms were also associated with worse OS.

CONCLUSIONS

BMs in patients with NENs remain underdiagnosed and undertreated. Recommendations for management of BMs derived from current knowledge are provided. Prospective studies to inform management are required.