Additional information gained by positron emission tomography with (68)Ga-DOTATOC for suspected unknown primary or recurrent neuroendocrine tumors

Diagnostic performance of various imaging modalities in localizing ectopic ACTH syndrome: A systematic review

BACKGROUND

To elucidate the role of various imaging modalities for tumor localization in ectopic ACTH Cushing's syndrome (EAS).

DESIGN AND METHOD

Systematic review of the literature published between January 2015-2024 was performed. Patients (290 EAS patients, 23.8% Occult) who underwent contrast enhanced CT (CECT) and at least one PET/CT-scan (68Ga-SSTR, FDG and/or F-DOPA) were included.

RESULTS

The sensitivity for identifying EAS tumor was comparable across CECT (63.1%, n=290), SSTR-PET/CT (58.2%, n=187), and FDG-PET/CT (57.6%, n=191), but was poor for DOPA-PET/CT (30.8%, n=26). Sensitivity for detecting metastasis was also comparable across CECT (78%, n=73), SSTR-PET/CT (85.3%, n=41), and FDG-PET (73.7%, n=38). For localised lesions, sensitivity as per etiology and grade of NET were similar for three scans, with exception of Thymic NET and grade 1 NET where CECT was better than FDG PET/CT. In patients not localised on CECT, sensitivity of SSTR PET/CT was 33.3% (vs. 18.9% FDG-PET/CT) whereas for patients negative on CECT and FDG-PET, sensitivity of SSTR-PET/CT was 15%. In cases where CECT and SSTR-PET/CT failed to localize, the sensitivities of FDG-PET/CT and DOPA-PET/CT were only 5.7% (2/35) and 0% (0/9), respectively. SSTR-PET/CT has a distinct advantage with significantly lesser false positive (FP) lesions (2.6%, mostly in thyroid/or pancreas). In comparison, CECT and FDG-PET/CT had FP ∼11% (mostly in lung and/or mediastinum), most of which were negative on SSTR-PET/CT.

CONCLUSIONS

As per the current evidence, SSTR-PET/CT can be considered as the scan of choice in EAS evaluation, and further research is needed as one-fourth of the lesions remain occult.

68 Ga-DOTATATE PET/CT in the Initial Diagnosis of Patients With Clinical, Imaging, and/or Biochemical Suspicion of a Neuroendocrine Tumor

PURPOSE

The aim of this study was to assess the yield of somatostatin receptor PET in patients with clinical, imaging, and/or biochemical suspicion of a neuroendocrine tumor (NET).

PATIENTS AND METHODS

This analysis includes patients referred for the initial diagnosis of an unconfirmed NET, as part of a prospective, single-arm registry study (NCT03873870) assessing the utility of 68 Ga-DOTATATE PET/CT in the management of NETs. Inclusion criteria to this cohort consisted of elevated biomarkers and/or clinical presentation suspicious for a NET, with negative conventional cross-sectional imaging, or presence of a lesion suspicious for a NET on conventional imaging, not amenable for biopsy. Patients with histological confirmation of a NET were excluded.

RESULTS

There were 220 patients included between April 2019 and March 2022 with a mean age ± SD of 59.5 ± 16.1 years with biochemical, morphological, and/or clinical suspicion of a NET. Overall, 132/220 patients (60%) had a positive 68 Ga-DOTATATE PET/CT. 68 Ga-DOTATATE PET/CT confirmed a type 2 somatostatin receptor overexpressing tumor in 123/171 (71.9%) of patients with a radiographically suspicious abnormality. The positivity rate for pancreatic, small bowel/mesenteric, adrenal, and other sites was 78/96 (81.2%), 38/57 (66.7%), 7/7 (100%), and 1/11 (9.1%), respectively. 68 Ga-DOTATATE PET/CT was positive in 9/49 (18.4%) of those with a biochemical and/or clinical suspicion of a NET.

CONCLUSIONS

68 Ga-DOTATATE PET/CT is positive in nearly 3 of 4 patients with morphological suspicion of a NET, with the highest yield in those with pancreatic and small bowel or mesenteric masses, and in approximately 1 of 6 patients with biochemical and/or clinical suspicion of a NET.

Prognostic Implications of PET-Derived Tumor Volume and Uptake in Patients with Neuroendocrine Tumors

Historically, molecular imaging of somatostatin receptor (SSTR) expression in patients with neuroendocrine tumors (NET) was performed using SSTR scintigraphy (SRS). Sustained advances in medical imaging have led to its gradual replacement with SSTR positron-emission tomography (SSTR-PET). The higher sensitivity in comparison to SRS on the one hand and conventional cross-sectional imaging, on the other hand, enables more accurate staging and allows for image quantification. In addition, in recent years, a growing body of evidence has assessed the prognostic implications of SSTR-PET-derived prognostic biomarkers for NET patients, with the aim of risk stratification, outcome prognostication, and prediction of response to peptide receptor radionuclide therapy. In this narrative review, we give an overview of studies examining the prognostic value of advanced SSTR-PET-derived (semi-)quantitative metrics like tumor volume, uptake, and composite metrics. Complementing this analysis, a discussion of the current trends, clinical implications, and future directions is provided.

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.

Treatment Outcomes in Patients with Metastatic Neuroendocrine Tumors: a Retrospective Analysis of a Community Oncology Database

Purpose

Metastatic neuroendocrine tumors (mNETs) are rare, heterogeneous tumors that present diagnostic and treatment challenges, with limited data on the management of mNETs in clinical practice. The present study was designed to identify current diagnostic and treatment patterns in mNET patients treated in the US community oncology setting.

Methods

Patient-level data was collected from medical records of adults with mNETs from the Vector Oncology Data Warehouse, a comprehensive US community oncology network database.

Results

Of the 263 patients included (median follow-up, 22 months; range, 0.1–193.9), 30.4% (80/263) had intestinal tumors, 11.0% (29/263) had pancreatic, and 58.6% (154/263) had tumors of other or unknown location. Progression-free survival (PFS) from the start of first-line therapy differed significantly by tumor grade (log rank P = 0.0016) and location (P = 0.0044), as did overall survival (OS) (grade, P < 0.0001; location, P = 0.0068). Median PFS and OS for patients with undocumented tumor grade were shorter than for patients with G1/G2 tumors and longer than patients with G3 tumors. Median PFS and OS for patients with other or unknown tumors were shorter than for patients with intestinal tumors.

Conclusions

While potentially confounded by the high number of patients with other or unknown tumor locations, this retrospective study of patients in a US community oncology setting identified the importance of awareness of tumor grade and tumor location at diagnosis, as these were direct correlates of PFS and OS.

Diagnostic utility of Gallium-68-somatostatin receptor PET/CT in ectopic ACTH-secreting tumors: a systematic literature review and single-center clinical experience

PURPOSE

Tumors causing ectopic Cushing's syndrome (ECS) are often not visible with conventional imaging. Gallium-68-DOTATATE, DOTATOC, and DOTANOC positron emission tomography/computed tomography (⁶⁸Ga-SSTR PET/CT) reportedly exhibits greater sensitivity in identifying an ECS source, however, evidence is limited to mainly case reports and a few small retrospective studies. Previous systematic ECS imaging review has shown ⁶⁸Ga-SSTR PET/CT sensitivity is similar to CT (81.8%) in histologically-proven cases and is 100% in covert-cases, however, the number of patients was small and no occult cases were reported.

METHODS

We performed a systematic literature review of ⁶⁸Ga-SSTR PET/CT use in ECS patients. We also report 6 consecutive patients with confirmed active and occult ECS who underwent ⁶⁸Ga-DOTATATE PET/CT and were followed at our institution between 2014 and 2019.

RESULTS

We identified 33 articles (23 case-reports, 4 case-series, 5 retrospective studies and 1 prospective study) detailing ⁶⁸Ga-SSTR PET/CT in 69 ECS patients. Overall ⁶⁸Ga-SSTR PET/CT sensitivity was 64.0%, while in histologically confirmed cases (67 lesions), sensitivity was 76.1%. There were two false-positives cases, both in the adrenal glands. In covert cases, ⁶⁸Ga-SSTR PET/CT identified 50% of lesions. There were ten occult cases where all imaging failed to identify an adrenocorticotropic hormone source; source remains unknown. In our case series, ⁶⁸Ga-DOTATATE PET/CT showed decreased uptake in pancreatic neuroendocrine tumor in one patient and did not help identify an ECS source in 5 patients.

CONCLUSION

Both this systematic literature review, the largest to date, and our single- center experience demonstrate a lower than previously reported ⁶⁸Ga-SSTR PET/CT sensitivity for ECS, especially in occult lesions. We suggest that the data on ⁶⁸Ga-SSTR PET/CT in ECS is subject to publication bias, and false-negatives are likely underreported; it's diagnostic value for ECS needs further study.

Detection rate of unknown primary tumour by using somatostatin receptor PET/CT in patients with metastatic neuroendocrine tumours: a meta-analysis

PURPOSE

The high diagnostic performance of somatostatin receptor positron emission tomography with computed tomography (PET/CT) in neuroendocrine tumours (NETs) was demonstrated by several articles. However, only some studies evaluated the detection rate (DR) of this imaging method in patients with metastatic NETs and unknown primary tumours (CUP-NETs). Therefore, we aimed to perform a meta-analysis to add evidence-based data in this setting.

METHODS

A comprehensive computer literature search of studies listed in PubMed/MEDLINE, EMBASE, and Cochrane library databases through December 2018 and regarding the use of somatostatin receptor PET/CT in patients with CUP-NETs was carried out. Pooled DR of CUP-NETs by using somatostatin receptor PET/CT was calculated. A pooled analysis evaluating the percentage of change of management by using somatostatin receptor PET/CT in these patients was also performed.

RESULTS

Twelve studies on the use of somatostatin receptor PET/CT in detecting CUP-NETs in 383 metastatic patients were included. The meta-analysis of all these studies provided the following DR on a per patient-based analysis: 56% (95% confidence interval (95% CI): 48-63%). Moderate heterogeneity among the selected studies was found (I² = 50%), whereas a significant publication bias was excluded by Egger's test (p = 0.45). The most common primary tumour sites were the bowel and the pancreas. A change of management by using somatostatin receptor PET/CT was demonstrated in 20% (95% CI: 10-33%) of patients with CUP-NET.

CONCLUSIONS

Somatostatin receptor PET/CT is very useful in detecting CUP-NETs in patients with metastatic disease. More studies on the change of management by using this imaging method in this setting are needed.

68Ga-DOTATOC and 18F-FDG PET/CT for identifying the primary lesions of suspected and metastatic neuroendocrine tumors: A prospective study in Taiwan

BACKGROUND/PURPOSE

To investigate the diagnostic accuracy of 68Ga-DOTATOC and 18F-FDG PET/CT to identify the primary foci in Taiwanese patients with clinically suspected neuroendocrine tumors (NET) and NET of unknown primary site.

METHODS

Patients with clinically suspected NET and NET of unknown primary site were eligible. All participants underwent a conventional workup (including CT, MR, endoscopic ultrasound), 68Ga-DOTATOC, and 18F-FDG PET/CT. The results of pathology and findings on clinical follow-up served as the gold standard.

RESULTS

Among the 36 patients included in the study, we were able to identify the primary tumor in 17 participants (47.2%). The overall sensitivity values of 68Ga-DOTATOC, 18F-FDG, and conventional workup were 88%, 41%, and 53%, respectively, whereas the specificities were 100%, 100%, 68%, respectively. The areas under curve of 68Ga-DOTATOC, 18F-FDG, and conventional workup were 0.941, 0.706, and 0.607, respectively. 68Ga-DOTATOC was more sensitive than 18F-FDG and more specific than conventional workup. Treatment changes as a result of 68Ga-DOTATOC PET/CT findings occurred in 12 (33.3%) of the 36 study participants.

CONCLUSION

Our data confirm the usefulness of 68Ga-DOTATOC in the identification of NET. In addition, treatment modifications as a result of 68Ga-DOTATOC PET/CT findings were evident in approximately one third of NET patients.

The influence of elevated hormone levels on physiologic accumulation of 68Ga-DOTATOC

OBJECTIVE

PET/CT imaging with ⁶⁸Ga-1,4,7,10-tetraazacyclododecane-N,N',N″,N‴-tetraacetic acid-D-Phe¹-Tyr³-octreotide (DOTATOC) is useful in patients with neuroendocrine tumors (NETs). Functioning NETs by definition secrete abnormal levels of hormones, causing clinical symptoms. It is known that physiologic accumulation can be seen in some organs, but it remains unknown whether elevated hormone levels can affect the physiologic accumulation pattern of ⁶⁸Ga-DOTATOC. We aimed to investigate the influence of higher hormone levels on physiologic accumulation of ⁶⁸Ga-DOTATOC.

METHODS

A total of 167 patients with known or suspected NET lesions were enrolled in this study. The numbers of patients with elevations of ACTH, gastrin, insulin, and no elevation were 10, 25, 7, and 125, respectively. We compared the maximum standardized uptake value (SUVmax) in various organs of each group.

RESULTS

In the group with elevated ACTH levels, SUVmax in the pituitary gland, the uncinate process of the pancreas and adrenal glands was lower than those in the group with no elevation (5.7 ± 1.9 vs. 8.4 ± 3.1, P = 0.015; 4.7 ± 3.5 vs. 6.4 ± 2.8, P = 0.037; 10.8 ± 4.8 vs. 13.9 ± 4.7, P = 0.020, respectively). There were no differences in physiologic uptake of ⁶⁸Ga-DOTATOC in the thyroid gland, the pancreatic body, the liver, the spleen, the bowel, or the kidney.

CONCLUSIONS

In NET patients with elevated ACTH levels, physiologic uptake of ⁶⁸Ga-DOTATOC in the pituitary gland, the uncinate process of the pancreas and adrenal glands was significantly decreased. Other organs were unaffected.

68Ga-DOTATOC Imaging of Neuroendocrine Tumors: A Systematic Review and Metaanalysis

68Ga-DOTATOC, a somatostatin receptor-targeted ligand, has been used clinically in Europe over the past decade for imaging neuroendocrine tumors (NETs). It appears to be quite sensitive and effective for clinical management decision making. This metaanalysis summarizes the efficacy of 68Ga-DOTATOC for several distinct indications and is intended to support approval of this agent by the U.S. Food and Drug Administration. Methods: The major electronic medical databases were searched for relevant papers over the period from January 2001 to November 2015. Papers were selected for review in 3 categories: clinical trials that reported sensitivity and specificity, comparison studies with 111In-octreotide, and change of management studies. All the eligible papers underwent Quality Assessment of Diagnostic Accuracy Studies (QUADAS) assessment, which was useful in the final selection of papers for review. Results: The initial search yielded 468 papers. After detailed evaluation, 17 papers were finally selected. Five types of studies emerged: workup of patients with symptoms and biomarker findings suggestive of NET, but with negative conventional imaging (3 papers, yield was only 13%); sensitivity (12 papers; sensitivity, 92%) and specificity (7 papers; specificity, 82%); identification of site of unknown primary in patients with metastatic NET (4 papers, yield was 44%); impact on subsequent NET patient management (4 papers, change in management in 51%); and comparison with 111In-octreotide (2 papers, sensitivity of DOTATOC on a per-lesion basis was 100%, for 111In-octreotide it was 78.2%; specificity was not available). Safety was not explicitly addressed in any study, but there were no reports of adverse events. Conclusion:68Ga-DOTATOC is useful for evaluating the presence and extent in disease for staging and restaging and for assisting in treatment decision making for patients with NET. It is also effective in locating the site of an unknown primary in NET patients who present with metastatic NET, but no known primary tumor. It also appears to be more accurate than 111In-octreotide. Although 68Ga-DOTATOC would seem to be useful in evaluating patients with suggestive symptoms and biomarker findings, it does not perform well in this setting and has low yield. Overall, it appears to be an excellent imaging agent to assess patients with known NET and frequently leads to a change in management.

Guidelines for the management of neuroendocrine tumours by the Brazilian gastrointestinal tumour group

Neuroendocrine tumours are a heterogeneous group of diseases with a significant variety of diagnostic tests and treatment modalities. Guidelines were developed by North American and European groups to recommend their best management. However, local particularities and relativisms found worldwide led us to create Brazilian guidelines. Our consensus considered the best feasible strategies in an environment involving more limited resources. We believe that our recommendations may be extended to other countries with similar economic standards.

[Management of gastrinoma]

Gastrinoma is a very rare tumor leading to gastrin hypersecretion and characterised by Zollinger-Ellisson syndrome (ZES) i.e. severe gastric and duodenal ulceration and profuse diarrhea. This disease can be sporadic or familial within a multiple endocrine neoplasia type 1 (MEN-1) syndrome. Diagnosis is based on hypergastrinemia/hypercholrhydria. Tumors are usually located in the duodeno-pancreas. Preoperative tumor location by CT, echoendoscopy and fibroscopy is not always possible because of the small size of the lesion that are frequently multiple. The aim of gastrinoma treatment is 1/to control the hormonal hypersecretion 2/to remove the neoplasm when it is possible. Surgery is the only chance to cure. Gastrinoma is a slow-growing tumor, and overall survival is good with a median survival above 10years and a 5-year survival above 80 % in surgically resected patients. Recurrence is frequent, a biochemical recurrence is observed in 65 % of cases and morphological recurrence in 40 % of patients at 2years. Metastases are associated with a dismal prognosis.

Clinical efficacy of dual-phase scanning using (68)Ga-DOTATOC-PET/CT in the detection of neuroendocrine tumours

AIM

To investigate whether delayed scanning at approximately 90 minutes post-injection of (68)Ga-labelled 1,4,7,10-tetraazacyclododecane-N,N',N″,N‴-tetraacetic acid-d-Phe(1)-Tyr(3)-octreotide (DOTATOC) had any clinical benefits regarding the evaluation of neuroendocrine tumours (NETs), relative to conventional combined positron-emission tomography (PET) and computed tomography (CT) at 60 minutes post-injection.

MATERIALS AND METHODS

Fifty-four patients who underwent DOTATOC-PET/CT for suspected or known NETs were retrospectively reviewed. PET/CT was performed twice at approximately 60 and 90 minutes post-injection. For visual analysis, a five-point grading scale (0: definitely normal to 4: definitely abnormal) was used, and grade 3-4 lesions were regarded as positive. For quantitative analysis, the time course of the maximum standardised uptake value (SUVmax) in each lesion and the mean SUV of physiological uptake in the liver were evaluated.

RESULTS

Of the 54 patients, 43 had a total of 132 lesions. In interpreting the early images, there were four grade 3 lesions, and the remaining 128 lesions were grade 4. All 132 lesions were grade 4 in the delayed images. SUVs and tumour-to-liver ratios for hepatic lesions were slightly higher in delayed scanning than in early scanning (SUV, 26.8±21.2 versus 28.2±21.2 [p<0.01]; tumour-to-liver ratio, 5.9±4.5 versus 6.2±4.6 [p<0.01]), which did not affect the detection rate. Additionally, bone and peritoneal metastases had slightly higher SUVs at delayed imaging (p<0.05), but there was no difference in diagnostic performance. No significant difference in the SUVs for pancreatic lesions and primary sites in the bowel were observed between the early and delayed scans.

CONCLUSION

Delayed scanning may be helpful for improving diagnostic confidence in some cases, although it provided no specific merits for diagnostic accuracy in detecting primary or metastatic NETs.