Correlation of somatostatin receptor PET/CT imaging features and immunohistochemistry in neuroendocrine tumors of the lung: a retrospective observational study

Histologic Ex Vivo Validation of the [18F]SITATE Somatostatin Receptor PET Tracer

Radiolabeled somatostatin analogs (SSAs), such as [68Ga]Ga-DOTA SSAs, have transformed imaging and therapeutic strategies. However, their use is constrained by the high cost of generators and their short half-life. In contrast, [18F]SITATE presents a promising alternative, offering the advantage of a longer half-life than 68Ga, along with the cost-effectiveness of cyclotron-based production. This study evaluated the first histologic ex vivo validation of [18F]SITATE. Methods: This study retrospectively included 47 patients (57% male; mean age, 66.9 ± 14.9 y) with histologically confirmed well-differentiated neuroendocrine neoplasms who underwent [18F]SITATE PET followed by surgery within 4 mo. Lesion uptake was quantified using SUVmean, SUVpeak, SUVmax, and tumor-to-liver ratio (TLR). Histologic somatostatin receptor (SSTR) type 2 expression was determined using histological scores (H-scores), with thresholds defining SSTR scores 1-3. The accuracy of PET imaging for preoperative metastatic detection was evaluated against surgical histology. Results: PET imaging demonstrated a significant correlation between [18F]SITATE uptake (SUVmean and TLR) and SSTR type 2 H-scores (r = 0.618 and 0.622, respectively; P < 0.0001). SSTR score 3 correlated with increased SUVmean and TLR (P < 0.0001). Among 35 patients with primary resection and lymphadenectomy, PET achieved a sensitivity of 73.9% and specificity of 100%. Conclusion: [18F]SITATE PET imaging strongly correlates with histologic SSTR expression, demonstrating utility in staging and guiding therapeutic decisions in neuroendocrine neoplasms. This 18F-labeled tracer shows specificity comparable to historical [68Ga]Ga-DOTA SSA data, whereas an increase in sensitivity for the detection of locoregional metastases appears possible. Further head-to-head comparisons of [18F]SITATE with traditional [68Ga]Ga-DOTA SSA and histologic validation are warranted to optimize its diagnostic accuracy and clinical impact.

Identification of Defined Molecular Subgroups on the Basis of Immunohistochemical Analyses and Potential Therapeutic Vulnerabilities of Pulmonary Carcinoids

INTRODUCTION

Multi-omic studies have identified three molecular separated pulmonary carcinoid (PC) subgroups (A1, A2, B) with distinctive mRNA expression profiles (e.g., orthopedia homeobox protein [OTP], achaete-scute homolog [ASCL1], and hepatocyte nuclear factor 1 homeobox A [HNF1A]). We aimed to establish an immunohistochemical (IHC) biomarker panel that enables subgroup identification, and assessment of its potential clinical relevance.

METHODS

All patients with resected pulmonary carcinoids (2003-2012) were identified from the Dutch Cancer/Pathology Registry, and tumors were revised. The IHC expression of OTP, ASCL1, and HNF1A was scored in a blinded fashion in a mRNA-profiled (n = 5 per subgroup) and national carcinoid cohort (N = 478). The expression of potential therapeutic targets (somatostatin receptor type 2a [SSTR2A] and delta-like canonical Notch ligand 3 [DLL3]) was assessed. Immunohistochemistry was assessed using H-scoring.

RESULTS

OTP, ASCL1, and HNF1A reported similar IHC and mRNA expression patterns in the matched primary samples. In the national cohort, IHC separated PCs into subgroups A1 (n = 224 [53%], OTPhigh-ASCL1high-HNF1Alow), A2 (n = 161 [38%], OTPhigh-ASCL1low-HNF1Ahigh), and B (n = 37 [9%], OTPlow-ASCL1low-HNF1Ahigh). In 12% of PCs, no distinct classification could be provided. Patients with A1 were enriched for older age (83% > 50 y), female individuals (83%), and peripheral location (55%) with low SSTR2A (median = 10) and high DLL3 (median = 52) expression. A2 included younger patients (34% < 40 y) and endobronchial/central (87%) tumors with high SSTR2A (median = 160), but low DLL3 (median 0) expression. Group B included more male individuals (59%) and recurrence was more frequent (19%) than in groups A1 (8%) and A2 (6%). Neuroendocrine cell hyperplasia was enriched in A1 (25%) compared with A2 (3%) and B (0%).

CONCLUSIONS

An OTP, ASCL1, and HNF1A IHC panel enables the identification of molecular-defined pulmonary carcinoid subgroups with distinct clinical phenotypes and diverging therapeutic vulnerabilities that require further prospective evaluation.

Comparison of 68Ga-DOTANOC and 18F-FDOPA PET/CT for Detection of Recurrent or Metastatic Paragangliomas

Purpose To evaluate the diagnostic performance of gallium 68 (68Ga)-DOTA-NaI3-octreotide (68Ga-DOTANOC) and fluorine 18 (18F)-fluoro-l-3,4-dihydroxyphenylalanine (18F-FDOPA) PET/CT in detecting recurrent or metastatic paragangliomas. Materials and Methods This single-center retrospective study included patients with paragangliomas who underwent both 68Ga-DOTANOC PET/CT and 18F-FDOPA PET/CT between August 2021 and December 2023. The diagnostic performance of these two tracers in detecting recurrent or metastatic tumors was compared using several metrics, including sensitivity, negative predictive value, and accuracy. Results This study included 36 patients (median age, 52 years [range, 14-78 years]; 16 female, 20 male). Of these, nine underwent initial 68Ga-DOTANOC and 18F-FDOPA PET/CT examinations before treatment, and the remaining 27 underwent posttreatment examinations. Twenty-two of those 27 patients had recurrence or metastasis. According to lesion-level analysis, 68Ga-DOTANOC had higher sensitivity, negative predictive value, and accuracy for diagnosis of bone metastases than did 18F-FDOPA PET/CT (97% vs 78% [P < .001], 85% vs 42% [P = .02], and 97% vs 81% [P < .001], respectively). 18F-FDOPA PET/CT had higher sensitivity, negative predictive value, and accuracy for the diagnosis of liver metastases than did 68Ga-DOTANOC PET/CT (73% vs 15% [P < .001], 68% vs 41% [P = .04], and 83% vs 46% [P < .001], respectively). According to patient-level analysis, the sensitivity of 18F-FDOPA PET/CT for diagnosing liver metastases was higher than that of 68Ga-DOTANOC PET/CT (88% vs 25%; P = .04). Conclusion In patients with recurrent or metastatic paragangliomas, 68Ga-DOTANOC PET/CT showed better performance than 18F-FDOPA PET/CT in detecting bone metastases, and 18F-FDOPA PET/CT performed better in detecting liver metastases. Keywords: 68Ga-DOTANOC, 18F-FDOPA, Pheochromocytoma, Paraganglioma Published under a CC BY 4.0 license.

Somatostatin Receptor Imaging in the Diagnosis and Management of Parathyroid Neuroendocrine Neoplasia

BACKGROUND

Parathyroid tumors are classified as parathyroid neuroendocrine neoplasia (NEN) by the IARC-WHO classification. These tumors can occur with NENs from other sites, which often require total-body [68Ga]-DOTA-peptides PET/CT. This study aimed to assess the utility of [68Ga]-DOTA-peptide PET/CT in imaging parathyroid NENs and to evaluate the underlying mechanisms.

METHODS

Fifty patients with primary hyperparathyroidism (PHPT) and parathyroid NENs histologically confirmed as parathyroid adenomas (PAs) were included. PET/CT with [68Ga]-DOTA-peptide was performed in 16 patients with localized PAs, including 10 with MEN1 syndrome. Somatostatin receptor types 2 and 5 (SST2 and SST5) staining was performed on PAs from 48 patients. Somatostatin analogs (SSA) were prescribed in four patients with MEN 1 syndrome and 1 with persistent acromegaly, all with PAs and PHPT. The therapy effects on calcium and parathyroid hormone (iPTH) were evaluated.

RESULTS

[68Ga]-DOTA-peptide PET/CT detected 20 PAs with high radiopharmaceutical uptake. SST2 expression was negative on PA cell membranes in all cases and positive on endothelium in 39 (81%) PAs. Membrane SST5 expression was positive in 25 (52%) PAs and endothelial was positive in 40 (83%). Serum calcium levels decreased in patients on SSA therapy, while iPTH did not.

CONCLUSIONS

PET/CT with [68Ga]-DOTA-peptides can detect parathyroid NENs. The incidental detection of high [68Ga]-DOTA-peptide uptake in the parathyroid region during whole-body PET/CT may prompt biochemical evaluation for PHPT. We suggest that endothelial SST expression mediates high radiopharmaceutical uptake by PAs and that SSA treatment can reduce hypercalcemia in PHPT patients.

Gallium-68 labeled somatostatin receptor antagonist PET/CT in over 500 patients with neuroendocrine neoplasms: experience from a single center in China

PURPOSE

Somatostatin receptor antagonists have shown promising performance for imaging neuroendocrine neoplasms. However, there is a lack of studies exploring the diagnostic performance of SSTR antagonists or comparing them with agonists in a large cohort of patients with NENs. This study aimed to retrospectively review all SSTR antagonist PET/CT scans conducted at Peking Union Medical College Hospital since November 2018 in patients with confirmed or suspected NENs.

METHODS

Four types of SSTR antagonists were utilized, including [68Ga]Ga-NODAGA-LM3, [68Ga]Ga-DOTA-LM3, [68Ga]Ga-NODAGA-JR11, and [68Ga]Ga-DOTA-JR11. The reference standard was based on a combination of histopathology, clinical evaluation, imaging results, and follow-up. Patient-based sensitivity, specificity, and accuracy were evaluated. The SUVmax and tumor-to-liver ratio (TLR) of the hottest lesions was recorded and compared between antagonists and [68Ga]Ga-DOTATATE.

RESULTS

A total of 622 antagonist scans from 549 patients were included in the analysis. The patient-level sensitivity, specificity, and accuracy of antagonist imaging (all tracers combined) were 91.0% (443/487), 91.9% (57/62), and 91.1% (500/549), respectively. In 181 patients with a comparative [68Ga]Ga-DOTATATE PET/CT scan, the patient-level sensitivity, specificity, and accuracy were 87.5% (147/168), 76.9% (10/13), and 86.7% (157/181), respectively. For the hottest lesions, SSTR antagonists all tracers combined demonstrated an overall comparable SUVmax to [68Ga]Ga-DOTATATE (40.1 ± 32.5 vs. 39.4 ± 23.8, p = 0.772). While [68Ga]Ga-NODAGA-LM3 showed significantly higher uptake than [68Ga]Ga-DOTATATE (57.4 ± 38.5 vs. 40.0 ± 22.8, p<0.001), [68Ga]Ga-NODAGA-JR11 (39.7 ± 26.5 vs. 34.3 ± 23.9, p = 0.108) and [68Ga]Ga-DOTA-LM3 (38.9 ± 32.1 vs. 37.2 ± 22.1, p = 0.858) showed comparable uptake to [68Ga]Ga-DOTATATE, and [68Ga]Ga-DOTA-JR11 showed lower uptake (28.9 ± 26.1 vs. 44.0 ± 25.7, p = 0.001). All antagonists exhibited significantly higher TLR than [68Ga]Ga-DOTATATE (12.1 ± 10.8 vs. 5.2 ± 4.5, p<0.001).

CONCLUSION

Gallium-68 labeled SSTR antagonists could serve as alternatives to SSTR agonists for imaging of NENs. Among various antagonists, [68Ga]Ga-NODAGA-LM3 seems to have the best imaging profile.

Percutaneous computed tomography-guided core needle biopsy can be used to histologically confirm the clinical features and long-term prognosis of pulmonary neuroendocrine neoplasms

PURPOSE

We investigated the clinical features and prognosis outcomes of pulmonary neuroendocrine neoplasms (PNENs) which were histologically confirmed after percutaneous computed tomography-guided core needle biopsy (PCT-CNB).

MATERIALS AND METHODS

We retrospectively investigated 173 patients who had PNENs which were histologically confirmed after PCT-CNB; patients were split into low and intermediate-grade neuroendocrine tumor (LIGNET) (typical carcinoid (TC) and atypical carcinoid (AC)) and high-grade neuroendocrine carcinoma-tumor (HGNEC) groups. In this latter group, patients were further subdivided into large-cell neuroendocrine carcinoma (LCNEC), small-cell lung cancer (SCLC), and high-grade neuroendocrine carcinoma-not otherwise specified (HGNEC-NOS) groups. Complications after biopsy were recorded. We also assessed overall survival (OS) rates using Kaplan-Meier curves, with prognostic factors determined using univariate and multivariate analyses.

RESULTS

Complications were mainly pneumothorax (22.5; 39/173 patients), chest tube placement (4.0; 7/173 patients), and pulmonary bleeding (33.5%; 58/173 procedures)-no patient mortality was recorded. Definitive diagnoses were ascribed to 102 SCLC, 10 LCNEC, 43 HGNEC-NOS, 7 TC, and 11 AC patients. The 1- and 3-year OS rates in the LIGNET group were 87.5% and 68.1%, respectively, and 59.2 and 20.9% in the HGNEC group, respectively these data were statistically significant (P = 0.010). For SCLC, 1- and 3-year OS rates were 63.3 and 22.3%, 30.0 and 10.0% for LCNEC, and 53.3% and 20.1% for HGNEC-NOS, respectively (P = 0.031). Independent prognostic factors for OS included disease type and distant metastasis.

CONCLUSION

PNENs may be pathologically diagnosed using PCT-CNB. While differential diagnoses between LCNEC and SCLC are problematic in some patients, a HGNEC-NOS diagnosis was ascribed and PCT-CNB samples were shown to predict NEN OS rates.

Somatostatin Receptor Expression in Lung Neuroendocrine Tumors: An Analysis of DOTATATE PET Scans

Somatostatin receptor (SSTR) expression in metastatic lung neuroendocrine tumors (NETs) has not been well characterized using PET imaging. Understanding the degree and uniformity of SSTR expression is important to establish the role of SSTR-targeted treatments in lung NETs. Methods: A retrospective institutional review of patients with metastatic lung NETs who underwent DOTATATE PET imaging from March 2017 to February 2023 was performed. Results: In total, 48 patients with metastatic lung NETs who underwent 68Ga- or 64Cu-DOTATATE PET imaging were identified. Four had completely negative SSTR expression, and 10 had very weak expression (less than in a normal liver). Among the remaining 34 patients, 21 had uniformly positive DOTATATE PET scans, and 13 had heterogeneous expression. Only 44% had uniformly positive receptor expression, identifying them as candidates for peptide receptor radionuclide therapy. Conclusion: Most metastatic lung NETs lack uniform SSTR expression and are thus suboptimal candidates for SSTR-targeted therapy. SSTR imaging in lung NETs should be evaluated carefully for uniformity of expression.

Diagnostic accuracy of SSR-PET/CT compared to histopathology in the identification of liver metastases from well-differentiated neuroendocrine tumors

BACKGROUND

Histopathology is the reference standard for diagnosing liver metastases of neuroendocrine tumors (NETs). Somatostatin receptor-positron emission tomography / computed tomography (SSR-PET/CT) has emerged as a promising non-invasive imaging modality for staging NETs. We aimed to assess the diagnostic accuracy of SSR-PET/CT in the identification of liver metastases in patients with proven NETs compared to histopathology.

METHODS

Histopathologic reports of 139 resected or biopsied liver lesions of patients with known NET were correlated with matching SSR-PET/CTs and the positive/negative predictive value (PPV/NPV), sensitivity, specificity, and diagnostic accuracy of SSR-PET/CT were evaluated. PET/CT reading was performed by one expert reader blinded to histopathology and clinical data.

RESULTS

133 of 139 (95.7%) liver lesions showed malignant SSR-uptake in PET/CT while initial histopathology reported on 'liver metastases of NET´ in 127 (91.4%) cases, giving a PPV of 91.0%. Re-biopsy of the initially histopathologically negative lesions (reference standard) nevertheless diagnosed 'liver metastases of NET' in 6 cases, improving the PPV of PET/CT to 95.5%. Reasons for initial false-negative histopathology were inadequate sampling in the sense of non-target biopsies. The 6 (4.3%) SSR-negative lesions were all G2 NETs with a Ki-67 between 2-15%.

CONCLUSION

SSR-PET/CT is a highly accurate imaging modality for the diagnosis of liver metastases in patients with proven NETs. However, we found that due to the well-known tumor heterogeneity of NETs, specifically in G2 NETs approximately 4-5% are SSR-negative and may require additional imaging with [18F]FDG PET/CT.

First preclinical evaluation of [225Ac]Ac-DOTA-JR11 and comparison with [177Lu]Lu-DOTA-JR11, alpha versus beta radionuclide therapy of NETs

BACKGROUND

The [¹⁷⁷Lu]Lu-DOTA-TATE mediated peptide receptor radionuclide therapy (PRRT) of neuroendocrine tumors (NETs) is sometimes leading to treatment resistance and disease recurrence. An interesting alternative could be the somatostatin antagonist, [¹⁷⁷Lu]Lu-DOTA-JR11, that demonstrated better biodistribution profile and higher tumor uptake than [¹⁷⁷Lu]Lu-DOTA-TATE. Furthermore, treatment with alpha emitters showed improvement of the therapeutic index of PRRT due to the high LET offered by the alpha particles compared to beta emitters. Therefore, [²²⁵Ac]Ac-DOTA-JR11 can be a potential candidate to improve the treatment of NETs (Graphical abstract). DOTA-JR11 was radiolabeled with [²²⁵Ac]Ac(NO₃)₃ and [¹⁷⁷Lu]LuCl₃. Stability studies were performed in phosphate buffered saline (PBS) and mouse serum. In vitro competitive binding assay has been carried out in U2OS-SSTR2 + cells for ^natLa-DOTA-JR11, ^natLu-DOTA-JR11 and DOTA-JR11. Ex vivo biodistribution studies were performed in mice inoculated with H69 cells at 4, 24, 48 and 72 h after injection of [²²⁵Ac]Ac-DOTA-JR11. A blocking group was included to verify uptake specificity. Dosimetry of selected organs was determined for [²²⁵Ac]Ac-DOTA-JR11 and [¹⁷⁷Lu]Lu-DOTA-JR11.

RESULTS

[²²⁵Ac]Ac-DOTA-JR11 has been successfully prepared and obtained in high radiochemical yield (RCY; 95%) and radiochemical purity (RCP; 94%). [²²⁵Ac]Ac-DOTA-JR11 showed reasonably good stability in PBS (77% intact radiopeptide at 24 h after incubation) and in mouse serum (~ 81% intact radiopeptide 24 h after incubation). [¹⁷⁷Lu]Lu-DOTA-JR11 demonstrated excellent stability in both media (> 93%) up to 24 h post incubation. Competitive binding assay revealed that complexation of DOTA-JR11 with ^natLa and ^natLu did not affect its binding affinity to SSTR2. Similar biodistribution profiles were observed for both radiopeptides, however, higher uptake was noticed in the kidneys, liver and bone for [²²⁵Ac]Ac-DOTA-JR11 than [¹⁷⁷Lu]Lu-DOTA-JR11.

CONCLUSION

[²²⁵Ac]Ac-DOTA-JR11 showed a higher absorbed dose in the kidneys compared to [¹⁷⁷Lu]Lu-DOTA-JR11, which may limit further studies with this radiopeptide. However, several strategies can be explored to reduce nephrotoxicity and offer opportunities for future clinical investigations with [²²⁵Ac]Ac-DOTA-JR11.

The diagnostic and prognostic role of combined [18F]FDG and [68Ga]-DOTA-peptides PET/CT in primary pulmonary carcinoids: a multicentric experience

OBJECTIVES

In the present retrospective multicentric study, we combined [68Ga]-DOTA-peptides and [18F]FDG-PET/CT findings aiming to investigate their capability to differentiate typical (TC) and atypical pulmonary carcinoids (AC) and their prognostic role.

METHODS

From three centers, 61 patients were retrospectively included. Based on a dual tracer combination we classified PET scans as score 1, [18F]FDG- and [68Ga]-DOTA-peptides negative; score 2, [68Ga]-DOTA-peptides positive and [18F]FDG-negative; score 3, [68Ga]-DOTA-peptides negative and [18F]FDG-positive; score 4, both tracers positive. Moreover, for each patient, the ratios of SUVmax on [68Ga]-DOTA-PET to that on [18F]FDG-PET were calculated (SUVr).

RESULTS

Thirty-five patients had a final diagnosis of TC. Twenty-two TC (57%) had positive [68Ga]-DOTA-peptides PET; instead, 21/26 (81%) AC had positive [18F]FDG-PET/CT. On dual-tracer analysis, scores 1, 2, 3 and 4 were 13%, 20%, 43% and 24% for all populations; 17%, 26%, 20% and 37% for TC; 8%, 11%, 73% and 8% for AC. Median SUVr was significantly higher in TC than AC (6.4 vs. 0.4, p = 0.011). The best value of SUVr to predict the final diagnosis was 1.05 (AUC 0.889). Relapse or progression of disease happened in 17 patients (11 affected by AC) and death in 10 cases (7 AC). AC diagnosis, positive [18F]FDG-PET, negative DOTA-PET and dual tracer score were significantly correlated with PFS (p = 0.013, p = 0.033, p = 0.029 and p = 0.019), while only AC diagnosis with OS (p = 0.022).

CONCLUSION

PET/CT findings had also a prognostic role in predicting PFS. Dual-tracer PET behavior may be used to predict the nature of pulmonary carcinoids and select the most appropriate management.

KEY POINTS

• Combination of [18F]FDG and [68Ga]-DOTA-peptides PET/CT results may help to differentiate between atypical and typical lung carcinoids. • The SUVmax ratio between [18F]FDG and [68Ga]-DOTA-peptides PET may help to differentiate between atypical and typical lung carcinoids. • Histotype and PET/CT features have a prognostic impact on PFS.

Somatostatin Receptor-Directed PET/CT for Therapeutic Decision-Making and Disease Control in Patients Affected With Small Cell Lung Cancer

BACKGROUND

Somatostatin receptor (SSTR)-targeted PET/CT is used for patients affected with small cell lung cancer (SCLC), but the clinical impact has not been elucidated yet. We aimed to determine whether SSTR PET/CT can trigger relevant therapeutic management changes in patients with SCLC and whether those modifications achieve disease control and are associated with prolonged survival.

METHODS

One hundred patients with SCLC received SSTR PET/CT. In a retrospective setting, we evaluated the diagnostic performance of PET versus CT and compared therapies before and after PET/CT to determine the impact of molecular imaging on treatment decision. We also determined the rate of disease control after therapeutic modifications and assessed survival in patients with and without changes in the therapeutic regimen.

RESULTS

Relative to CT, SSTR PET alone was superior for assessing bone lesions in 19 of 39 instances (49%). Treatment was modified in 59 of 100 (59%) after SSTR PET/CT. Forty of 59 (74.6%) received systemic treatment after hybrid imaging, with the remaining 15 of 59 (25.4%) scheduled for nonsystemic therapy. In the latter group, 13 of 15 (86.7%) received local radiation therapy or active surveillance (2/15 [13.3%]). Individuals scheduled for systemic treatment after imaging received peptide receptor radionuclide therapy (PRRT) in 28 of 44 (63.6%), followed by chemotherapy in 10 of 44 (22.7%), change in chemotherapy regimen in 3 of 44 (6.8%), and initiation of tyrosine kinase inhibitor in the remaining 3 of 44 (6.8%). Among patients with modified treatment, follow-up was available in 53 subjects, and disease control was achieved in 14 of 53 (26.4%). However, neither change to systemic treatment (155 days; hazard ratio, 0.94; 95% confidence interval, 0.53-1.67) nor change to nonsystemic treatment (210 days; hazard ratio, 0.67; 95% confidence interval, 0.34-1.34) led to a prolonged survival when compared with subjects with no change (171 days, P ≥ 0.22, respectively).

CONCLUSIONS

In patients with SCLC, SSTR-targeted hybrid imaging provides complementary information on the disease status. PET/CT led to management changes in 59% (mainly PRRT), achieving disease control in >26%. The high fraction of patients scheduled for PRRT may lay the foundation for combination strategies to achieve synergistic antitumor effects, for example, by combining PRRT plus recently introduced RNA polymerase II inhibitors.

The potential application of MR-derived ADCmin values from 68Ga-DOTATATE and 18F-FDG dual tracer PET/MR as replacements for FDG PET in assessment of grade and stage of pancreatic neuroendocrine tumors

BACKGROUND

To evaluate the utility of ⁶⁸Ga-DOTATATE and ¹⁸F-FDG PET/MR for prediction of grade and stage of pancreatic neuroendocrine tumors (PNETs), and to examine the correlation between parameters obtained from FDG PET and diffusion-weighted imaging (DWI) MR parameters.

METHODS

A retrospective study using ⁶⁸Ga-DOTATATE and ¹⁸F-FDG PET/MR imaging was performed between April 2020 and May 2022 on 46 individuals with histologically confirmed PNETs. Metabolic tumor volume (MTV), maximum standardized uptake value (FSUVmax), and tumor lesion glycolysis (TLG) for FDG; somatostatin receptor density (SRD), maximum standardized uptake value (GSUVmax), and total lesion somatostatin receptor density (TLSRD) for DOTATATE; and minimum and mean apparent diffusion coefficient (ADCmin and ADCmean) values for MRI, respectively. We performed Spearman's correlation analysis to examine the links between these variables and primary tumor stage and grading.

RESULTS

Higher PNET grading was associated with higher FSUVmax, MTV, and TLG values (P < 0.05). TLG, SRD, ADCmin, and ADCmean values were correlated with N staging, while SRD, MTV, ADCmin, TLG, and ADCmean were associated with M staging. Notably, ADCmin was a negative correlation between FSUVmax (r =  - 0.52; P < 0.001), MTV (r =  - 0.50; P < 0.001), and TLG (r =  - 0.56; P < 0.001).

CONCLUSIONS

This study highlights significant correlative relationships between FDG PET-derived parameters and ADCmin. ADCmin may offer utility as a tool for PNET staging and grading in lieu of FDG PET. ⁶⁸Ga-DOTATATE PET/MR alone may be a sufficient alternative to dual tracer PET/MR when conducting grading and staging of primary PNETs.