Imaging of pancreatic cancer: what the surgeon wants to know

Preoperative prediction of microvascular invasion and perineural invasion in pancreatic ductal adenocarcinoma with 18F-FDG PET/CT radiomics analysis

AIM

To develop and validate a predictive model based on 2-[¹⁸F]-fluoro-2-deoxy-d-glucose (¹⁸F-FDG) positron-emission tomography (PET)/computed tomography (CT) radiomics features and clinicopathological parameters to preoperatively identify microvascular invasion (MVI) and perineural invasion (PNI), which are important predictors of poor prognosis in patients with pancreatic ductal adenocarcinoma (PDAC).

MATERIALS AND METHODS

Preoperative ¹⁸F-FDG PET/CT images and clinicopathological parameters of 170 patients in PDAC were collected retrospectively. The whole tumour and its peritumoural variants (tumour dilated with 3, 5, and 10 mm pixels) were applied to add tumour periphery information. A feature-selection algorithm was employed to mine mono-modality and fused feature subsets, then conducted binary classification using gradient boosted decision trees.

RESULTS

For MVI prediction, the model performed best on a fused subset of ¹⁸F-FDG PET/CT radiomics features and two clinicopathological parameters, with an area under the receiver operating characteristic curve (AUC) of 83.08%, accuracy of 78.82%, recall of 75.08%, precision of 75.5%, and F1-score of 74.59%. For PNI prediction, the model achieved best prediction results only on the subset of PET/CT radiomics features, with AUC of 94%, accuracy of 89.33%, recall of 90%, precision of 87.81%, and F1 score of 88.35%. In both models, 3 mm dilation on the tumour volume produced the best results.

CONCLUSIONS

The radiomics predictors from preoperative ¹⁸F-FDG PET/CT imaging exhibited instructive predictive efficacy in the identification of MVI and PNI status preoperatively in PDAC. Peritumoural information was shown to assist in MVI and PNI predictions.

Comparison of minimal invasive versus open radical antegrade modular pancreatosplenectomy (RAMPS) for pancreatic ductal adenocarcinoma: a single center retrospective study

INTRODUCTION

Radical antegrade modular pancreatosplenectomy (RAMPS) was proposed a decade ago with the aim to achieve higher R0 tangential margin and radical N1 lymph node resection for left-sided pancreatic adenocarcinoma (PDAC), which has been widely accepted worldwide at present. Laparoscopic RAMPS (Lap-RAMPS) has been attempted for PDAC during last several years, however, no outcomes evaluation by comparison between laparoscopic vs open RAMPS has been reported yet.

MATERIALS AND METHODS

From August, 2012 to March, 2018, patients undergoing open or lap-RAMPS for the diagnosis of left-sided PDAC were reviewed from a prospective database. Patients excluded if they were related with combined organs or vessels resection, systematic metastasis as well as conversion from open RAMPS to lap RAMPS. The surgical and oncologic outcomes were compared.

RESULTS

A total of 48 PDAC patients were enrolled (25 underwent lap-RAMPS and 23 underwent open-RAMPS). There were no significant differences in demographic or perioperative morbidity. In the lap-RAMPS group, R0 transection margin and retroperitoneal margin were both achieved in 23 of 25 patients (92%). In the open RAMPS group, R0 transection margin was achieved in 21 of 23 patients (91.3%), R0 retroperitoneal margin was 22 of 23 patients (95.65%). There were no differences in pathological examinations. The number of lymph node (LN) retrieved between lap-RAMPS and open- RAMPS group was not significant difference (15.84 vs 18.22; P = 0.268). Median disease-free survival (DFS) was analogous in two groups (18.11 m vs 20.00 m, P = 0.999). Median overall survival (OS) was 24.53 m in lap-RAMPS group and 28.73 m in the open-RAMPS group (P = 0.633).

CONCLUSIONS

Lap-RAMPS is technically feasible, and has comparable long-term oncological outcome with open-RMAPS.

Early Detection in a Mouse Model of Pancreatic Cancer by Imaging DNA Damage Response Signaling

Despite its widespread use in oncology, the PET radiotracer 18F-FDG is ineffective for improving early detection of pancreatic ductal adenocarcinoma (PDAC). An alternative strategy for early detection of pancreatic cancer involves visualization of high-grade pancreatic intraepithelial neoplasias (PanIN-3s), generally regarded as the noninvasive precursors of PDAC. The DNA damage response is known to be hyperactivated in late-stage PanINs. Therefore, we investigated whether the SPECT imaging agent 111In-anti-γH2AX-TAT allows visualization of the DNA damage repair marker γH2AX in PanIN-3s in an engineered mouse model of PDAC, to facilitate early detection of PDAC. Methods: Genetically engineered KPC (KRasLSL.G12D/+; p53LSL.R172H/+; PdxCre) mice were imaged with 18F-FDG and 111In-anti-γH2AX-TAT. The presence of PanIN/PDAC as visualized by histologic examination was compared with autoradiography and immunofluorescence. Separately, the survival of KPC mice imaged with 111In-anti-γH2AX-TAT was evaluated. Results: In KPC mouse pancreata, γH2AX expression was increased in high-grade PanINs but not in PDAC, corroborating earlier results obtained from human pancreas sections. Uptake of 111In-anti-γH2AX-TAT, but not 111In-IgG-TAT or 18F-FDG, within the pancreas correlated positively with the age of KPC mice, which correlated with the number of high-grade PanINs. 111In-anti-γH2AX-TAT localizes preferentially in high-grade PanIN lesions but not in established PDAC. Younger, non-tumor-bearing KPC mice that show uptake of 111In-anti-γH2AX-TAT in the pancreas survive for a significantly shorter time than mice with physiologic 111In-anti-γH2AX-TAT uptake. Conclusion:111In-anti-γH2AX-TAT imaging allows noninvasive detection of DNA damage repair signaling upregulation in preinvasive PanIN lesions and is a promising new tool to aid in the early detection and staging of pancreatic cancer.

Computed tomography features of acinar cell carcinoma of the pancreas

PURPOSE

To report the computed tomography (CT) features of pancreatic acinar cell carcinoma (ACC) and identify CT features that may help discriminate between pancreatic ACC and pancreatic ductal adenocarcinoma (PDA).

MATERIALS AND METHODS

The CT examinations of 20 patients (13 men, 7 women; mean age, 66.5±10.7 [SD] years; range: 51-88 years) with 20 histopathologically proven pancreatic ACC were reviewed. CT images were analyzed qualitatively and quantitatively and compared to those obtained in 20 patients with PDA. Comparisons were performed using univariate analysis with a conditional logistic regression model.

RESULTS

Pancreatic ACC presented as an enhancing (20/20; 100%), oval (15/20; 75%), well-delineated (14/20; 70%) and purely solid (13/20; 65%) pancreatic mass with a mean diameter of 52.6±28.0 (SD) mm (range: 24-120mm) in association with visible lymph nodes (14/20; 70%). At univariate analysis, well-defined margins (Odds ratio [OR], 7.00; P=0.005), nondilated bile ducts (OR, 9.00; P=0.007), visible lymph nodes (OR, 4.33; P=0.028) and adjacent organ involvement (OR, 5.67; P=0.02) were the most discriminating CT features to differentiate pancreatic ACC from PDA. When present, lymph nodes were larger in patients with pancreatic ACC (14±4.8 [SD]; range: 7-25mm) than in those with PDA (8.8±4.1 [SD]; range: 5-15mm) (P=0.039).

CONCLUSION

On CT, pancreatic ACC presents as an enhancing, predominantly oval and purely solid pancreatic mass that most frequently present with no bile duct dilatation, no visible lymph nodes, no adjacent organ involvement and larger visible lymph nodes compared to PDA.

Clinical Translation of a 68Ga-Labeled Integrin αvβ6-Targeting Cyclic Radiotracer for PET Imaging of Pancreatic Cancer

The overexpression of integrin α_vβ₆ in pancreatic cancer makes it a promising target for noninvasive PET imaging. However, currently, most integrin α_vβ₆-targeting radiotracers are based on linear peptides, which are quickly degraded in the serum by proteinases. Herein, we aimed to develop and assess a ⁶⁸Ga-labeled integrin α_vβ₆-targeting cyclic peptide (⁶⁸Ga-cycratide) for PET imaging of pancreatic cancer. Methods: ⁶⁸Ga-cycratide was prepared, and its PET imaging profile was compared with that of the linear peptide (⁶⁸Ga-linear-pep) in an integrin α_vβ₆-positive BxPC-3 human pancreatic cancer mouse model. Five healthy volunteers (2 women and 3 men) underwent whole-body PET/CT imaging after injection of ⁶⁸Ga-cycratide, and biodistribution and dosimetry were calculated. PET/CT imaging of 2 patients was performed to investigate the potential role of ⁶⁸Ga-cycratide in pancreatic cancer diagnosis and treatment monitoring. Results: ⁶⁸Ga-cycratide exhibited significantly higher tumor uptake than did ⁶⁸Ga-linear-pep in BxPC-3 tumor-bearing mice, owing-at least in part-to markedly improved in vivo stability. ⁶⁸Ga-cycratide could sensitively detect the pancreatic cancer lesions in an orthotopic mouse model and was well tolerated in all healthy volunteers. Preliminary PET/CT imaging in patients with pancreatic cancer demonstrated that ⁶⁸Ga-cycratide was comparable to ¹⁸F-FDG for diagnostic imaging and postsurgery tumor relapse monitoring. Conclusion: ⁶⁸Ga-cycratide is an integrin α_vβ₆-specific PET radiotracer with favorable pharmacokinetics and a favorable dosimetry profile. ⁶⁸Ga-cycratide is expected to provide an effective noninvasive PET strategy for pancreatic cancer lesion detection and therapy response monitoring.

MR imaging features of pancreatic acinar cell carcinoma

PURPOSE

This study aimed to report the magnetic resonance imaging (MRI) features of acinar cell carcinoma (ACC) of the pancreas including diffusion-weighted MRI findings.

MATERIALS AND METHODS

The MRI examinations of five patients (3 men, 2 women; median age, 61years) with histopathologically proven ACC of the pancreas were retrospectively reviewed. MR images were analyzed qualitatively (location, shape, homogeneity, signal intensity, vascular involvement and extrapancreatic extent of ACC) and quantitatively (tumor size, apparent diffusion coefficient [ADC] and normalized ADC of ACC).

RESULTS

All ACC were visible on MRI, presenting as an oval pancreatic mass (5/5; 100%), with moderate and heterogeneous enhancement (5/5; 100%), with a median transverse diameter of 43mm (Q₁, 35; Q₃, 82mm; range: 30-91mm). Tumor capsule was visible in 4/5 ACC (80%) and Wirsung duct enlargement in 2/5 ACC (40%). On diffusion-weighted MRI, all ACC (5/5; 100%) were hyperintense on the 3 b value images. Median ADC value of ACC was 1.061×10^-3mm²/s (Q₁, 0.870×10^-3mm²/s; Q₃, 1.138×10^-3mm²/s; range: 0.834-1.195×10^-3mm²/s). Median normalized ADC ratio of ACC was 1.127 (Q₁, 1.071; Q₃, 1.237; range: 1.054-1.244).

CONCLUSIONS

On MRI, ACC of the pancreas presents as a large, oval pancreatic mass with moderate and heterogeneous enhancement after intravenous administration of a gadolinium chelate, with restricted diffusion and a median ADC value of 1.061×10^-3mm²/s on diffusion-weighted MRI. Further studies however are needed to confirm our findings obtained in a limited number of patients.

A Novel Physiobiological Parameter-Based Grading System for Resectable Pancreatic Cancer

BACKGROUND

Preoperative methods to estimate disease-specific survival (DSS) for resectable pancreatic cancer are limited.

OBJECTIVE

The aim of this study was to develop and validate a pretreatment physiobiological prognostic model in patients with radiologically resectable pancreatic cancer.

METHODS

A retrospective review of a prospectively maintained institutional database was undertaken to identify patients who underwent potentially curative resection for radiologically resectable pancreatic cancer. Demographics, treatments, and relationships between the potential prognostic factors and survival rate were analyzed, and prognostic nomograms were established.

RESULTS

We identified 240 patients who fulfilled our eligible criteria. The 1-, 3-, and 5-year DSS rates after surgery were 77.8, 40.9, and 31.3%, respectively. On multivariate analysis, increased neutrophil/lymphocyte ratio [hazard ratio (HR) 1.60, 95% confidence interval (CI) 1.17-2.17; p < 0.01], reduced Prognostic Nutritional Index (HR 2.08, 95% CI 1.68-3.20; p < 0.01), and elevated preoperative serum carbohydrate antigen 19-9 level (HR 2.12, 95% CI 1.55-2.88; p < 0.01) were associated with worse DSS. Although curative resection was the operative aim for all patients, 131 (54.6%) patients had recurrence within 12 months after curative resection of resectable pancreatic cancer. There was a significant correlation between recurrence pattern and physiobiological characteristics.

CONCLUSION

We developed a new grading system for radiologically resectable pancreatic cancer. This system is simple and reliably predicts differences in survival after pancreatic resection.

Early detection of pancreatic cancer in mouse models using a novel antibody, TAB004

Pancreatic ductal adenocarcinoma (PDA) is the fourth-leading cause of cancer death in the United States with a 5-year overall survival rate of 8% for all stages combined. But this decreases to 3% for the majority of patients that present with stage IV PDA at time of diagnosis. The lack of distinct early symptoms for PDA is one of the primary reasons for the late diagnosis. Common symptoms like weight loss, abdominal and back pains, and jaundice are often mistaken for symptoms of other issues and do not appear until the cancer has progressed to a late stage. Thus the development of novel imaging platforms for PDA is crucial for the early detection of the disease. MUC1 is a tumor-associated antigen (tMUC1) expressed on 80% of PDA. The goal of this study was to determine the targeting and detection capabilities of a tMUC1 specific antibody, TAB004. TAB004 antibody conjugated to a near infrared fluorescent probe was injected intraperitoneally into immune competent orthotopic and spontaneous models of PDA. Results show that fluorophore conjugated TAB004 specifically targets a) 1 week old small tumor in the pancreas in an orthotopic PDA model and b) very early pre-neoplastic lesions (PanIN lesions) that develop in the spontaneous PDA model before progression to adenocarcinoma. Thus, TAB004 is a promising antibody to deliver imaging agents directly to the pancreatic tumor microenvironment, significantly affecting early detection of PDA.

The Role of 18F-FDG PET/CT and PET/MRI in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) remains a difficult disease to treat and continues to portend a poor prognosis, as most patients are unresectable at diagnosis. 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) combined with CT (PET/CT) has been a cornerstone in oncological imaging of different cancers; however, the role of PET/CT in PDAC is continually evolving and currently not well established. Studies have shown the potential of PET/CT in guiding the management of patients with PDAC, with possible added benefit over anatomic imaging with CT or MRI in certain scenarios. PET/CT may be useful in diagnosis, initial staging, treatment response assessment, differentiation of recurrent tumor from post-treatment fibrosis, and radiotherapy planning. Additionally, PET/CT may be a cost-effective modality due to upstaging of patients originally deemed as surgical candidates. Recently, the advent of simultaneous PET/MRI represents an exciting advancement in hybrid functional imaging with potential applications in the imaging of PDAC. The advantages of PET/MRI include simultaneous acquisition to improve registration of fusion images, lower radiation dose, superior soft tissue contrast, and availability of multiparametric imaging. Studies are underway to evaluate the utility of PET/MRI in PDAC, including in initial staging and treatment response assessment and to determine the subgroup of patients that will benefit from PET/MRI. Further studies are warranted in both PET/CR and PET/MRI to better understand the role of these modalities in PDAC.

Irreversible electroporation of pancreatic adenocarcinoma: a primer for the radiologist

Irreversible electroporation (IRE) is increasingly used for the ablation of unresectable locally advanced pancreatic adenocarcinoma. Unlike other ablation technologies that cannot be safely used around critical vasculature or ducts for risk of thermal damage, IRE uses high-voltage pulses to disrupt cellular membranes. This causes cell death by apoptosis and inflammation. IRE has been deployed by both open and percutaneous approaches. Generator parameters are the same for both approaches, and settings are pancreas specific. Variations in settings, probe placement, and probe exposure can result in thermal damage or reversible electroporation and resultant treatment failure, morbidity, or mortality. When used properly, IRE appears to improve overall survival and local recurrence, but does not influence the rate of distant recurrence. However, studies of both open and percutaneous approaches have been relatively small, non-controlled, and without appropriate comparisons. It is challenging for the radiologist to interpret treatment effects after IRE because of a dearth of guiding literature and pathologic correlates. This primer describes technical aspects, pathology correlates, post-IRE imaging, and outcomes for percutaneous and open approaches.