PET–Computed Tomography and Precision Medicine in Pancreatic Adenocarcinoma and Pancreatic Neuroendocrine Tumors

Expression of TIGAR and its correlation with clinicopathology, prognosis, and 18F-FDG PET/CT parameters in patients with resectable pancreatic ductal adenocarcinoma

OBJECTIVE

The aim of this study was to investigate the expression of TP53-inducible glycolysis and apoptosis regulator (TIGAR) and its relationship with clinical pathology and prognosis; and to analyze the correlation between TIGAR expression and 18F-labeled fluoro-2-deoxyglucose (18F-FDG) PET/computed tomography (CT) parameters in patients with pancreatic ductal adenocarcinoma (PDAC).

METHODS

We retrospectively analyzed the data of 23 patients who underwent preoperative 18F-FDG PET/CT examinations and were confirmed to have PDAC by postoperative pathology. TIGAR was detected using immunohistochemistry. The relationships between TIGAR expression and clinicopathology and its value in predicting the prognosis of patients with PDAC were analyzed. The correlations between TIGAR expression and 18F-FDG PET/CT parameters [standard uptake value (SUV) max, SUVmean, SUVpeak, metabolic tumor volume (MTV), and total lesion glycolysis (TLG)] were analyzed.

RESULTS

The expression of TIGAR was low in 34.8% of patients and high in 65.2% of patients. There was no correlation between TIGAR expression and clinicopathology. The overall survival of patients with high TIGAR expression was significantly shorter than that of patients with low TIGAR expression (11.2 vs. 35.4 months). The 18F-FDG PET/CT parameters: SUVmax, SUVmean, SUVpeak, MTV, and TLG were positively correlated with TIGAR expression, but only the MTV correlation with TIGAR expression was statistically significant.

CONCLUSION

TIGAR is highly expressed in PDAC. Its expression is independent of clinicopathological data and can be used as an independent prognostic factor. TIGAR expression was significantly positively correlated with the 18F-FDG PET/CT parameter MTV.

Pancreatic Schwannoma on FDG PET/CT

A 55-year-old woman underwent FDG PET/CT to evaluate a pancreatic mass. The images showed elevated FDG activity in the uncinated process of the pancreas, suggestive of malignancy. However, pathological examination from the resected lesion demonstrated pancreatic schwannoma.

FDG PET/CT Imaging of Pancreatic Plasmacytoma

A 56-year-old man underwent F-FDG PET/CT to evaluate possible pancreatic cancer, which was revealed by CT. The images showed a solid lesion with peripherally increased FDG activity in the tail of the pancreas, as well as hypermetabolic lesions in the lumbar spine and rib. Pathological examination following lumbar biopsy demonstrated multiple myeloma. Five months after chemotherapy, follow-up FDG PET/CT showed cystic change in the pancreatic lesion without elevated metabolism.

Complementary role of computed tomography texture analysis for differentiation of pancreatic ductal adenocarcinoma from pancreatic neuroendocrine tumors in the portal-venous enhancement phase

Purpose

To assess the role of CT-texture analysis (CTTA) for differentiation of pancreatic ductal adenocarcinoma (PDAC) from pancreatic neuroendocrine neoplasm (PNEN) in the portal-venous phase as compared with visual assessment and tumor-to-pancreas attenuation ratios.

Methods

53 patients (66.1 ± 8.6y) with PDAC and 42 patients (65.5 ± 12.2y) with PNEN who underwent contrast-enhanced CT for primary staging were evaluated. Volumes of interests (VOIs) were set in the tumor tissue at the portal-venous phase excluding adjacent structures. Based on pyradiomics library, 92 textural features were extracted including 1st, 2nd, and higher order features, and then compared between PNEN and PDAC. The visual assessment classified tumors into hypo-, iso-, or hyperdense to pancreas parenchyma or into homogeneous/heterogeneous. Additionally, attenuation ratios between the tumors and the non-involved pancreas were calculated.

Results

8/92 (8.6%) highly significant (p < 0.005) discriminatory textural features between PDAC and PNEN were identified including the 1st order features “median,” “total energy,” “energy,” “10th percentile,” “90th percentile,” “minimum,” “maximum,” and the 2nd order feature “Gray-Level co-occurrence Matrix (GLCM) Informational Measure of Correlation (Imc2).” In PNEN, the higher order feature “GLSZM Small Area High Gray-Level Emphasis” proved significantly higher in G1 compared to G2/3 tumors (p < 0.05). The tumor/parenchyma ratios as well as the visual assessment into hypo-/iso-/hyperdense or homogeneous/heterogeneous did not significantly differ between PDAC and PNEN.

Conclusions

Our data indicate that CTTA is a feasible tool for differentiation of PNEN from PDAC and also of G1 from G2/3 PNEN in the portal-venous phase. Visual assessment and tumor-to-parenchyma ratios were not useful for discrimination.

Electronic supplementary material

The online version of this article (10.1007/s00261-020-02406-9) contains supplementary material, which is available to authorized users.

Differential diagnosis of solid pancreatic masses

Solid pancreatic lesions include mainly adenocarcinoma, neuroendocrine tumors pancreatic cystic neoplasms with solid component, solid pseudopapillary tumor, pancreatoblastoma, pancreatic lymphoma, and pancreatic metastasis. The most frequent pancreatic lesion is the adenocarcinoma, representing between 70% and 95% of all solid pancreatic neoplasm. The diagnosis of these lesions can be a challenge and currently, there are different imaging techniques such as CT scan, EUS and MRI with high sensitivity and specificity. The most widely used technique for the initial evaluation is the CT scan with a sensitivity between 76% and 92% for the diagnosis of pancreatic cancer. The EUS has a sensitivity for the detection of pancreatic lesions of around 98% and is accepted to be the most sensitive technique for the detection of small pancreatic tumors (<2 cm). The MRI, with a very high soft-tissue contrast resolution, provides an accuracy in the detection and staging of adenocarcinoma of 90-100%. A multimodality approach is usually necessary in patients with clinical suspicion of pancreatic lesion. The EUS is required for the local evaluation of the relation of the lesion with vessels and for tissue acquisition and the CT scan and/or MRI is usually required for the local and distance staging in case of pancreatic cancer. The purpose of this review is to provide an overview of solid pancreatic lesions and the role of the different imaging techniques in their evaluation.