Imaging of pancreatic neoplasms

Incidence of Postoperative Complications Following Pancreatectomy for Pancreatic Cystic Lesions or Pancreatic Cancer

BACKGROUND

In contrast to pancreatic ductal adenocarcinoma (PDAC), the risks of pancreatectomy for mucinous pancreatic cysts (MCs) are balanced against the putative goal of removing potentially malignant tumors. Despite undergoing similar operations, different rates of perioperative complications and morbidity between MC and PDAC patient populations may affect recommendations for resection. We therefore sought to compare the rates of postoperative complications between patients undergoing pancreatectomies for MCs or PDAC.

METHODS

A prospectively maintained institutional database was used to identify patients who underwent surgical resection for MCs or PDAC from July 2011 to August 2019. Patient demographics, complications, and perioperative data were compared between groups.

RESULTS

A total of 103 patients underwent surgical resection for MCs and 428 patients underwent resection for PDAC. Combined major 90-day postoperative complications were similar between MC and PDAC patients undergoing pancreaticoduodenectomy (PD, 32.5% vs. 20.0%, p = 0.068) or distal pancreatectomy (DP, 30.2% vs. 20.5%, p = 0.172). The most frequent complications were postoperative pancreatic fistula (POPF), abscess, and postoperative bleeding. The incidence of 90-day ISGPS Grade B/C POPF was higher in cyst patients undergoing PD (17.5% vs. 4.1%, p = 0.003) but not DP (25.4% vs. 20.5%, p = 0.473). No significant differences in operative time or length of stay between MCs and PDAC cohorts were observed.

CONCLUSIONS

POPFs occur more frequently and at higher grades in patients undergoing PD for MCs than for PDAC and should inform patient selection. Accordingly, the perioperative management of MC patients undergoing PD should emphasize POPF risk mitigation.

Quantitative Software Analysis of Endoscopic Ultrasound Images of Pancreatic Cystic Lesions

Endoscopic ultrasonography (EUS) is the most accurate imaging modality for the evaluation of different types of pancreatic cystic lesions. Our aim was to analyze EUS images of pancreatic cystic lesions using an image processing software. We specified the echogenicity of the lesions by measuring the gray value of pixels inside the selected areas. The images were divided into groups (serous cystic neoplasm /SCN/, intraductal papillary mucinous neoplasms and mucinous cystic neoplasms /Non-SCN/ and Pseudocyst) according to the pathology results of the lesions. Overall, 170 images were processed by the software: 81 in Non-SCN, 30 in SCN and 59 in Pseudocyst group. The mean gray value of the entire lesion in the Non-SCN group was significantly higher than in the SCN group (27.8 vs. 18.8; p < 0.0005). The area ratio in the SCN, Non-SCN and Pseudocyst groups was 57%, 39% and 61%, respectively; significantly lower in the Non-SCN group than in the SCN or Pseudocyst groups (p < 0.0005 and p < 0.0005, respectively). The lesion density was also significantly higher in the Non-SCN group compared to the SCN or Pseudocyst groups (4186.6/mm2 vs. 2833.8/mm2 vs. 2981.6/mm2; p < 0.0005 and p < 0.0005, respectively). The EUS image analysis process may have the potential to be a diagnostic tool for the evaluation and differentiation of pancreatic cystic lesions.

Exosomal circular RNA hsa_circ_0006220, and hsa_circ_0001666 as biomarkers in the diagnosis of pancreatic cancer

BACKGROUND

Pancreatic cancer is a highly malignant tumor of the digestive system.

OBJECTIVE

Exosomal circular RNA can be used as a biomarker for the early diagnosis of pancreatic cancer.

METHODS

The expression of various differentially expressed circRNAs in pancreatic cancer tissues was analyzed by gene chip, exosome expression was verified by electron microscopy and Western blotting, and the expression of exosomal circRNA in pancreatic cancer cells, tissues, and plasma were determined by quantitative reverse transcription-polymerase chain reaction (qRT-PCR).

RESULTS

Compared with healthy controls, hsa_circ_0006220 and hsa_circ_0001666 were highly expressed in exosomes in the plasma of pancreatic cancer patients. The AUC values were 0.7817 for hsa_circ_0006220, 0.8062 for hsa_circ_0001666, and 0.884 for the combined diagnosis. In addition, clinicopathological features revealed that the expression of hsa_circ_0006220 in plasma exosomes from pancreatic cancer patients was associated with CA19-9 levels (p = 0.0001) and lymph node metastasis (p = 0.0005). The expression of hsa_circ_0001666 was correlated with both tumor size (p = 0.0157) and CA19-9 level (p = 0.0001).

CONCLUSIONS

The high expression of exosomal hsa_circ_0001666 and hsa_circ_0006220 suggests that these can be used as new biomarkers for the diagnosis and treatment of pancreatic cancer.

Pancreatitis and PDAC: association and differentiation

The discrimination of mass-forming chronic pancreatitis (MFCP) from pancreatic ductal adenocarcinoma (PDAC) is a central diagnostic dilemma. It is important to differentiate these entities since they have markedly different prognoses and management. Importantly, the appearance of these two entities significantly overlaps on a variety of imaging modalities. However, there are imaging features that may be suggestive of one entity more than the other. MFCP and PDAC may show different enhancement patterns on perfusion computed tomography (CT) and/or dynamic contrast-enhanced MRI (DCE-MRI). The duct-penetrating sign on magnetic resonance cholangiopancreatography (MRCP) is more often associated with MFCP, whereas abrupt cutoff with upstream dilatation of the main pancreatic duct and the double-duct sign (obstruction/cutoff of both the common bile duct and pancreatic duct) are more often associated with PDAC. Nevertheless, tissue sampling is the most reliable method to differentiate between these entities and is currently generally necessary for management.

Molecular markers contribute to the clinical diagnosis for pancreatic cystic neoplasms

A pancreatic cystic neoplasm (PCN) is a rare pancreatic disease. Malignant PCNs are usually identified incidentally while evaluating other lesions. However, PCNs are being identified more frequently owing to the increased use of abdominal imaging. Malignant PCNs have complicated and diverse biological behaviors, including various malignant risk factors, diverse molecular features, natural history, and complex pathological classifications. Although many diagnostic methods, such as cross-sectional imaging and endoscopic evaluation, have been developed, malignant PCNs are still difficult to differentiate from benign tumors. On searching for related articles in the recent decade, we found that some molecular biomarkers such as carcinoembryonic antigen could be useful for discriminating between malignant tumors and benign tumors. However, cytopathologic evaluation is the most useful method for differentiating between benign and malignant lesions. Although cytopathologic evaluation has a specificity of 100% for identifying malignancies, its accuracy is often hampered by the low cellularity of PCN cells in the cystic fluid. Herein, we review the progress in the use of cellular and molecular markers for the accurate identification of PCNs.

Significance of Cancer Cells at the Vein Edge in Patients with Pancreatic Adenocarcinoma Following Pancreatectomy with Vein Resection

BACKGROUND

Resection of the superior mesenteric and/or portal vein (SMV-PV) is increasingly performed with pancreatectomy for adenocarcinoma. We sought to analyze the impact of cancer at the transected edge(s) of the vein wall.

METHODS

Patients who underwent pancreatectomy with vein resection between 2003 and 2015 at a single center were evaluated. R1 resection was defined per guidelines from the American Joint Commission on Cancer and the College of American Pathologists. Specimens were also evaluated for the presence (V+) or absence (V-) of cancer cells at the transected edge(s) and depth of vein invasion.

RESULTS

Among 127 evaluated patients, 114 (90%) received preoperative therapy. R-status was categorized as margin-negative (R0)/V- (n = 72, 57%), R0/V+ (n = 19, 15%), margin-positive (R1)/V- (n = 24, 19%), and R1/V+ (n = 12, 9%). Patients with V- specimens had similar median durations of recurrence-free survival (RFS) (12 vs 9 months) and overall survival (OS) (30 vs 28 months) as did patients with V+ specimens (P > 0.05). In contrast, cancer invasion into the lumen was associated with RFS and OS (P < 0.05). Among patients who underwent R0 resection, V-status had no association with OS, RFS, or local control (P > 0.05).

CONCLUSION

Cancer invasion into the superior mesenteric and/or portal vein was adversely associated with survival, but cancer at the vein edge(s) was not. Transection of the SMV-PV through macroscopically normal vein may be performed to minimize resected vein length without fear of negatively affecting oncologic outcomes.

Computed Tomography-Based Biomarker Outcomes in a Prospective Trial of Preoperative FOLFIRINOX and Chemoradiation for Borderline Resectable Pancreatic Cancer

PURPOSE

Effective preoperative regimens and biomarkers for pancreatic ductal adenocarcinoma (PDAC) are lacking. We prospectively evaluated fluorouracil, leucovorin, irinotecan, and oxaliplatin (FOLFIRINOX)-based treatment and imaging-based biomarkers for borderline resectable PDAC.

METHODS

Eligible patients had treatment-naïve, histology-confirmed PDAC and one or more high-risk features: mesenteric vessel involvement, CA 19-9 level of 500 mg/dL or greater, and indeterminate metastatic lesions. Patients received modified FOLFIRINOX and chemoradiation before anticipated pancreatectomy. Tumors were classified on baseline computed tomography as high delta (well-defined interface with parenchyma) or low delta (ill-defined interface). We designated computed tomography interface response after therapy as type I (remained or became well defined) or type II (became ill defined). The study had 80% power to differentiate a 60% from 40% resection rate (α = .10). Overall survival (OS) and progression-free survival (PFS) were estimated using the Kaplan-Meier method, and subgroups were compared using log-rank tests.

RESULTS

Thirty-three patients initiated therapy; 45% underwent pancreatectomy. The median OS was 24 months (95% CI, 16.2 to 29.6 months). For patients who did and did not undergo pancreatectomy, the median OS was 42 months (95% CI, 17.7 months to not estimable) and 14 months (95% CI, 9.0 to 24.8 months), respectively. Patients with high-delta tumors had lower 3-year PFS (4% v 40%) and 3-year OS rates (20% v 60%) than those with low-delta tumors (both P < .05). Patients with type II interface responses had lower 3-year PFS (0% v 29%) and 3-year OS rates (16% v 47%) than those with type I responses (both P < .001).

CONCLUSION

Preoperative FOLFIRINOX followed by chemoradiation for high-risk borderline resectable PDAC was associated with a resection rate of 45% and median OS of approximately 2 years. Our imaging-based biomarker validation indicates that personalized treatment may be achieved using these biomarkers at baseline and post-treatment.

First-Line Gemcitabine and Nab-Paclitaxel Chemotherapy for Localized Pancreatic Ductal Adenocarcinoma

BACKGROUND

Preoperative chemotherapy provides early treatment of micro-metastases and guaranteed delivery of all components of multimodality therapy for localized pancreatic ductal adenocarcinoma (PDAC). For locally advanced (LA) PDAC, induction chemotherapy is the standard of care. This study evaluated the use of gemcitabine and nab-paclitaxel (Gem/nab-P) as first-line therapy for localized PDAC.

METHODS

Clinicopathologic features, treatment, and outcomes were evaluated for 99 patients with localized PDAC. The patients were staged using previously published criteria as follows: potentially resectable (PR), borderline type A (BR-A) (anatomy amenable to vascular resection), BR-B (biology suspicious for metastatic disease including high CA19-9), BR-C (comorbidities requiring medical optimization), and LA.

RESULTS

The 99 patients (PR/BR/LA: 45/14/40) were treated with Gem/nab-P. Clinical staging showed that 20 patients had PR or BR-A disease, whereas 39 patients had BR-B or BR-C disease. The BR-B+C cases included one or more of the following: age of 80 years or older (13%), Eastern Cooperative Oncology Group performance status (ECOG PS) of 2 or more (13%), moderate to severe comorbidities (55%), CA19-9 of 1000 or higher (28%), and suspicion for metastases (21%). The majority of the patients received biweekly Gem/nab-P dosing, which was well tolerated. Pancreatectomy was performed for 12 (60%) of 20 patients with PR+BR-A, 2 (5%) of 39 patients with BR-B+C, and 1 (3%) of 40 patients with LA disease. During a median follow-up period of 26 months, the median overall survival (OS) period was 18 months (95% confidence interval [CI], 15.6-20.5 months) for all the patients, 17 months (95% CI, 14.6-19.5 months) for the unresected patients, and not reached for the resected patients (p = 0.028 for resected vs unresected patients).

CONCLUSIONS

A significant number of patients with radiographically resectable PDAC albeit aggressive biology (BR-B), medically inoperable conditions (BR-C), or both received biweekly first-line Gem/nab-P. The resection rates were lower for the BR-B/BR-C patients than for the PR/BR-A patients (hazard ratio [HR], 0.43; 95% CI, 0.19-1.00; p = 0.05).

Prognosis of Pancreatic Cancer Patients with Synchronous or Metachronous Malignancies from Other Organs Is Better than Those with Pancreatic Cancer Only

PURPOSE

Pancreatic cancer associated double primary tumors are rare and their clinicopathologic characteristics are not well elucidated.

MATERIALS AND METHODS

Clinicopathologic factors of 1,352 primary pancreatic cancers with or without associated double primary tumors were evaluated.

RESULTS

Of resected primary pancreatic cancers, 113 (8.4%) had associated double primary tumors, including 26 stomach, 25 colorectal, 18 lung, and 13 thyroid cancers. The median interval between the diagnoses of pancreatic cancer and associated double primary tumors was 0.5 months. Overall survival (OS) of pancreatic cancer patients with associated double primary tumors was longer than those with pancreatic cancer only (median, 23.1 months vs. 17.0 months, p=0.002). Patients whose pancreatic cancers were resected before the diagnosis of metachronous tumors had a better OS than patients whose pancreatic cancer resected after the diagnosis of metachronous tumors (48.9 months and 13.5 months, p=0.001) or those whose pancreatic cancers were resected synchronously with non-pancreas tumors (19.1 months, p=0.043). The OS of pancreatic cancer patients with stomach (33.9 months, p=0.032) and thyroid (117.8 months, p=0.049) cancers was significantly better than those with pancreas cancer only (17.0 months).

CONCLUSION

About 8% of resected pancreatic cancers had associated double primary tumors, and those from the colorectum, stomach, lung, and thyroid were common. Patients whose pancreatic cancer was resected before the diagnosis of metachronous tumors had better OS than those resected after the diagnosis of metachronous tumors or those resected synchronously.

Does Computed Tomography Have the Ability to Differentiate Aggressive From Nonaggressive Solid Pseudopapillary Neoplasm?

OBJECTIVE

The aim of the study was to assess the ability of contrast-enhanced computed tomography (CECT) to differentiate aggressive from nonaggressive solid pseudopapillary neoplasms (SPNs).

MATERIALS AND METHODS

Forty treatment-naive patients with pathologically proven pancreatic SPNs were included. Imaging characteristics were determined by consensus of 3 radiologists blinded to histopathologic aggressiveness. All patients underwent 4-phase CECT using a pancreatic protocol. The regions of interest of the tumor and the normal pancreas were documented on all phases. Lymph nodes were considered metastatic if greater than 1.0 cm in short-axis diameter.Fisher exact and Wilcoxon rank-sum tests were used to compare between aggressive and nonaggressive tumors.

RESULTS

No significant difference was noted between imaging covariates, such as internal hemorrhage, calcification, wall thickness perceptibility, vascular invasion, margins, cystic component, and pancreatic and biliary ductal dilation. Tumors with greater than 62.5 Hounsfield units and progressive enhancement during the delayed phase had aggressive characteristics (P = 0.03).

CONCLUSIONS

On delayed phase CECT, pathologically aggressive SPNs may show greater enhancement than nonaggressive SPNs.

Assessment of iodine uptake by pancreatic cancer following chemotherapy using dual-energy CT

Pancreatic cancer remains a major health problem, and only less than 20% of patients have resectable disease at the time of initial diagnosis. Systemic chemotherapy is often used in the patients with borderline resectable, locally advanced unresectable disease and metastatic disease. CT is often used to assess for therapeutic response; however, conventional imaging including CT may not correctly reflect treatment response after chemotherapy. Dual-energy (DE) CT can acquire datasets at two different photon spectra in a single CT acquisition, and permits separating materials and extract iodine by applying a material decomposition algorithm. Quantitative iodine mapping may have an added value over conventional CT imaging for monitoring the treatment effects in patients with pancreatic cancer and potentially serve as a unique biomarker for treatment response. In this pictorial essay, we will review the technique for iodine quantification of pancreatic cancer by DECT and discuss our observations of iodine quantification at baseline and after systemic chemotherapy with conventional cytotoxic agents, and illustrate example cases.

Proteome characterization of human pancreatic cyst fluid from intraductal papillary mucinous neoplasm by liquid chromatography/tandem mass spectrometry

RATIONALE

In recent years, the molecular components of pancreatic cyst fluid have been used for diagnosis and prognosis. Because the protein markers that are currently used in clinical tests are unreliable, proteomic studies to find new protein markers are being conducted. However, such researches have been limited due to the complexity of pancreatic cyst fluid and the immaturity of proteomic techniques.

METHODS

To overcome these limitations and provide a pancreatic cyst proteome dataset, we examined cyst fluid proteome with tandem mass spectrometry. The proteomic analysis was performed using a Orbitrap-based mass spectrometer (Q-Exactive) coupled with a 50-cm-long nano-liquid chromatography column. Protein mutations were identified using mutation sequence database search.

RESULTS

A total of 5850 protein groups were identified from microliters of cyst fluid. Among those, 3934 protein groups were reported for the first time in pancreatic cyst fluid. Although high-abundance proteins were not depleted in the experiment, our dataset detected almost all pancreatic tumor markers such as mucin family members, S100 proteins, and CEA-related proteins. In addition, 590 protein mutation marker candidates were discovered.

CONCLUSIONS

We provide a comprehensive cyst proteome dataset that includes cystic cellular proteins and mutated proteins. Our findings would serve as a rich resource for further IPMN studies and clinical applications. The MS data have been deposited in the ProteomeXchange with identifier PXD005671 (http://proteomecentral.proteomexchange.org/dataset/PXD005671).

Surgery management for sporadic small (≤2 cm), non-functioning pancreatic neuroendocrine tumors: a consensus statement by the Chinese Study Group for Neuroendocrine Tumors (CSNET)

The incidence of small (≤2 cm), non-functioning pancreatic neuroendocrine tumors (NF-pNETs) increased in the last decades. Before making appropriate strategy for patients with NF-pNETs ≤2 cm, pathological confirmation is vital. Incidentally diagnosed, sporadic small NF-pNETs may bring aggressive behavior and poor prognosis, such as extrapancreatic extension, lymph nodal metastasis, distant metastasis and recurrence, even causing disease-related death. Understanding and formulating an appropriate strategy for the patients with sporadic small, non-functioning pancreatic neuroendocrine tumors have been controversial for some time. Although several studies have reported that patients with NF-pNETs ≤2 cm had less rate of malignant behavior compared with larger ones (>2 cm); and the surgery approach may leading to surgery-related pancreatic complications; but there is still a lack of level I evidence to convince surgeons to abandon all cases with sporadic small NF-pNETs. Based on an updated literature search and review, the members of the Chinese Study Group for Neuroendocrine Tumors (CSNET) from high-volume centers have reached a consensus on the issue of the management strategy for the sporadic small NF-pNETs. We recommend that, except for some selected patients with NF-pNETs <1 cm, incidentally discovered and unacceptable surgical risks, all others with NF-pNETs ≤2 cm should undergo tumor resection with lymph node dissection or at least lymph node sampling and careful postoperative surveillance.

Definition and Management of Borderline Resectable Pancreatic Cancer

Patients with localized pancreatic ductal adenocarcinoma seek potentially curative treatment, but this group represents a spectrum of disease. Patients with borderline resectable primary tumors are a unique subset whose successful therapy requires a care team with expertise in medical care, imaging, surgery, medical oncology, and radiation oncology. This team must identify patients with borderline tumors then carefully prescribe and execute a combined treatment strategy with the highest possibility of cure. This article addresses the issues of clinical evaluation, imaging techniques, and criteria, as well as multidisciplinary treatment of patients with borderline resectable pancreatic ductal adenocarcinoma.

Role of Fluorouracil, Doxorubicin, and Streptozocin Therapy in the Preoperative Treatment of Localized Pancreatic Neuroendocrine Tumors

INTRODUCTION

5-Fluorouracil, doxorubicin, and streptozocin (FAS) leads to a 39 % response rate in advanced pancreatic neuroendocrine tumors (pNETs). We sought to validate our hypothesis that preoperative FAS may facilitate resection of locoregionally advanced pNETs by reducing the anatomic extent of the primary tumor.

PATIENTS

All patients who received FAS between 2000 and 2012 as initial therapy for a localized pNET were reviewed. Tumor size and vascular relationships were compared on pretreatment and posttreatment imaging studies to quantify treatment response.

RESULTS

Twenty-nine patients received a median 4 cycles of FAS (range 2-15). Rates of RECIST progressive disease (PD), stable disease (SD), and partial response (PR) were 3, 90, and 7 %, respectively. An interface was observed between the tumor and a major mesenteric artery and/or vein in 19 (66 %) and 24 (83 %) patients, respectively; after therapy with FAS, 17 (59 %) and 22 (76 %) had persistent interface with artery and/or vein. Fourteen (48 %) patients underwent pancreatectomy, 7 (50 %) required vascular management, and 9 (64 %) operations were R0. The median overall survival of unresected and resected patients was 41 months (95 % CI, 16-66) and 112 months (95 % CI, 104-120) (P = 0.04).

CONCLUSIONS

Although patients receiving FAS for locoregionally advanced pNETs are unlikely to progress during systemic therapy, significant "downstaging" appears uncommon.

Dynamic Contrast-Enhanced CT in Patients with Pancreatic Cancer

The aim of this systematic review is to provide an overview of the use of Dynamic Contrast-enhanced Computed Tomography (DCE-CT) in patients with pancreatic cancer. This study was composed according to the PRISMA guidelines 2009. The literature search was conducted in PubMed, Cochrane Library, EMBASE, and Web of Science databases to identify all relevant publications. The QUADAS-2 tool was implemented to assess the risk of bias and applicability concerns of each included study. The initial literature search yielded 483 publications. Thirteen articles were included. Articles were categorized into three groups: nine articles concerning primary diagnosis or staging, one article about tumor response to treatment, and three articles regarding scan techniques. In exocrine pancreatic tumors, measurements of blood flow in eight studies and blood volume in seven studies were significantly lower in tumor tissue, compared with measurements in pancreatic tissue outside of tumor, or normal pancreatic tissue in control groups of healthy volunteers. The studies were heterogeneous in the number of patients enrolled and scan protocols. Perfusion parameters measured and analyzed by DCE-CT might be useful in the investigation of characteristic vascular patterns of exocrine pancreatic tumors. Further clinical studies are desired for investigating the potential of DCE-CT in pancreatic tumors.

State-of-the-art Imaging of Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine tumors are rare tumors that present many imaging challenges, from detecting small functional tumors to fully staging large nonfunctioning tumors, including identifying all sites of metastatic disease, particularly nodal and hepatic, and depicting vascular involvement. The correct choice of imaging modality requires knowledge of the tumor type (eg, gastrinoma versus insulinoma), and also the histology (well vs poorly differentiated). Evolving techniques in computed tomography (CT), MRI, endoscopic ultrasonography, and nuclear medicine, such as dual-energy CT, diffusion-weighted MRI, liver-specific magnetic resonance contrast agents, and new nuclear medicine agents, offer new ways to visualize, and ultimately manage, these tumors.

Multidetector CT of pancreatic ductal adenocarcinoma: Effect of tube voltage and iodine load on tumour conspicuity and image quality

OBJECTIVES

To compare a low-tube-voltage with or without high-iodine-load multidetector CT (MDCT) protocol with a normal-tube-voltage, normal-iodine-load (standard) protocol in patients with pancreatic ductal adenocarcinoma (PDAC) with respect to tumour conspicuity and image quality.

METHODS

Thirty consecutive patients (mean age: 66 years, men/women: 14/16) preoperatively underwent triple-phase 64-channel MDCT examinations twice according to: (i) 120-kV standard protocol (PS; 0.75 g iodine (I)/kg body weight, n = 30) and (ii) 80-kV protocol A (PA; 0.75 g I/kg, n = 14) or protocol B (PB; 1 g I/kg, n = 16). Two independent readers evaluated tumour delineation and image quality blindly for all protocols. A third reader estimated the pancreas-to-tumour contrast-to-noise ratio (CNR). Statistical analysis was performed with the Chi-square test.

RESULTS

Tumour delineation was significantly better in PB and PA compared with PS (P = 0.02). The evaluation of image quality was similar for the three protocols (all, P > 0.05). The highest CNR was observed with PB and was significantly better compared to PA (P = 0.02) and PS (P = 0.0002).

CONCLUSION

In patients with PDAC, a low-tube-voltage, high-iodine-load protocol improves tumour delineation and CNR leading to higher tumour conspicuity compared to standard protocol MDCT.

KEY POINTS

• Low-tube-voltage high-iodine-load MDCT improves pancreatic cancer conspicuity compared to a standard protocol. • The pancreas-to-tumour attenuation difference increases significantly by reducing the tube voltage. • The radiation exposure dose decreases by reducing the tube voltage.

Anatomical, Physiological, and Molecular Imaging for Pancreatic Cancer: Current Clinical Use and Future Implications

Pancreatic adenocarcinoma is one of the deadliest human malignancies. Early detection is difficult and effective treatment is limited. Verifying the presence of micrometastatic dissemination and vessel invasion remains elusive, limiting radiological staging once this diagnosis is made. Diagnostic imaging provides independent tools to evaluate and characterize the biologic behavior of pancreatic cancer. Conventional anatomic imaging alone with either CT or MRI yields useful information on organ involvement but is limited in providing molecular and physiological information. Molecular imaging techniques such as PET or MRS provide information on metabolic and signaling pathways. Advanced MR sequences that target physiological parameters expand imaging options to characterize these tumors. By considering the parametric data from these three imaging approaches (anatomic, molecular, and physiological) we can better define specific tumor signatures. Such parametric characterization can provide insight into tumor metabolism, cellular density, protein expression, focal perfusion, and vascular permeability of these tumors. Radiogenomics research has already demonstrated ability to obtain information about cancer's genotype and phenotype; this is without invasive procedures or surgery. Further advances in these areas of experimental imaging hold promise to enable future clinical advances in detection and therapy of pancreatic cancer.

Differential diagnosis of pancreatic cancer by single-shot echo-planar imaging diffusion-weighted imaging

AIM: To investigate the diagnostic ability of single-shot echo-planar imaging (EPI) diffusion-weighted imaging (DWI) to differentiate between malignant and benign pancreatic lesions.

METHODS: A computerized search was performed on PubMed, MEDLINE and EMBASE up to August 2014. Nine studies (10 sets of data) with a total of 304 malignant pancreatic lesions and 188 benign pancreatic lesions were included. The characteristics of each study included the study name, year of publication, magnetic resonance modalities used, patient population, strength of field, pulse time, repetition time, echo time (TE), maximum b factor, mean age, mean body weight, fat suppression, number of benign and malignant lesions, and true positive, true negative, false positive and false negative results. All analyses were performed using Meta-DiSc and Stata 11.0.

RESULTS: The pooled sensitivity and specificity of single-shot EPI DWI were 0.83 (95%CI: 0.79-0.87) and 0.77 (95%CI: 0.70-0.83), respectively. The positive likelihood ratio and negative likelihood ratio were 5.09 (95%CI: 2.19-11.84) and 0.23 (95%CI: 0.15-0.36), respectively. The P value for the χ² heterogeneity for all pooled estimates was < 0.05. From the fitted summary receiver operating characteristic curve, the area under the curve and Q* index were 0.89 and 0.82, respectively. Publication bias was not present (t = 0.58, P = 0.58). Meta-regression analysis indicated that fat suppression, mean age, TE, and maximum b factor were not sources of heterogeneity (all P > 0.05).

CONCLUSION: Single-shot EPI DWI is useful to differentiate between malignant and benign pancreatic lesions. Lesion size ≥ 2 cm is the limit for the diagnosis of early lesions.

Use of Imaging for GI Cancers

GI cancers are a heterogeneous group of neoplasms that differ in their biologic and physical behaviors depending on the organ of origin, location within the organ, and degree of differentiation. As a result, evaluation of these tumors is complex, requiring integration of information from a patient's clinical history, physical examination, laboratory data, and imaging. With advances in anatomic and functional imaging techniques, we now have tools for assessing patients with these tumors at diagnosis, staging, and treatment assessment. It is difficult for a single imaging modality to provide all the necessary information for a given GI tumor. However, well-chosen combinations of available imaging modalities based on the indications, strength, and limitations of the modalities will provide optimal evaluation of patients with these malignancies.