Tumoral and nontumoral pancreas: correlation between quantitative dynamic contrast-enhanced MR imaging and histopathologic parameters

Personalized medicine in pancreatic cancer: the revolution has begun

Pancreatic ductal adenocarcinoma carries a dismal prognosis. Both chemotherapy and targeted therapies have been disappointing when administered to unselected populations. Recently, progress has been made in our understanding of the genomic landscape of this cancer which displays remarkable heterogeneity suggesting a reorientation of management and research strategies based on molecular characterization and adapted personalized therapy. Resectable disease offers new opportunities for translational research through functional imaging response evaluation and tumor tissue acquisition before and after neoadjuvant therapy. There is urgent need for clinical trials based on molecular profiling in pancreatic ductal adenocarcinoma. In this review we discuss opportunities and limitations of these new strategies, underlining the importance of tissue acquisition and integration of molecular biomarkers in future molecularly driven clinical trials.

Reproducibility of Dynamic Contrast-Enhanced MRI in Renal Cell Carcinoma: A Prospective Analysis on Intra- and Interobserver and Scan-Rescan Performance of Pharmacokinetic Parameters

The objective of this study was to investigate the intra- and interobserver as well as scan-rescan reproducibility of quantitative parameters of renal cell carcinomas (RCCs) with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). A total of 21 patients with clear cell RCCs (17 men, 4 woman; age 37-69 years, mean age 54.6 years, mean size, 5.0 ± 2.2 cm) were prospectively recruited from September 2012 to November 2012. Patients underwent paired DCE-MRI studies on a 3.0 T MR system with an interval of 48 to 72 hours. The extended-Tofts model and population-based arterial input function were used to calculate kinetic parameters. Three observers defined the 2-dimensional whole-tumor region of interest at the slice with the maximum diameter of the RCC. Intraobserver and scan-rescan differences were assessed using paired t tests, whereas interobserver differences using two-way analysis of variance. Intra- and interobserver reproducibility and scan-rescan reproducibility were evaluated using within-subject coefficient of variation (wCoV) and intraclass correlation coefficient (ICC). There were no significant intra-, interobserver, or scan-rescan differences in parameters (all P > 0.05). All ICCs for intra- and interobserver agreements were >0.75 (P < 0.05), whereas the scan-rescan agreement was moderate to good; V(e) (0.764, 95% confidence interval [CI]: 0.378-0.925) and K(ep) (0.906, 95% CI: 0.710-0.972) had higher ICC than K(trans) (0.686; 95% CI: 0.212-0.898) and V(p) (0.657; 95% CI: 0.164-0.888). In intra- and interobserver variability analyses, all parameters except V(p) had low wCoV values. K(trans) and V(e) had slightly lower intraobserver wCoV (1.2% and 0.9%) compared with K(ep) (3.7%), whereas all 3 of these parameters had similar interobserver wCoV values (2.5%, 3.1%, and 2.9%, respectively). Regarding scan-rescan variability, K(trans) and K(ep) showed slightly higher variation (15.6% and 15.4%) than V(e) (10.1%). V(p) had the largest wCoV in all variability analyses (all >30%). DCE-MRI demonstrated good intra- and interobserver reproducibility and moderate to good scan-rescan performance in the assessment of RCC using K(trans), K(ep), and V(e) as parameters under noncontinuous scanning mode. V(p) showed poor reproducibility, and thus may not be suitable for this scanning protocol.

Prognostication and response assessment in liver and pancreatic tumors: The new imaging

Diffusion-weighted imaging (DWI), dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and perfusion computed tomography (CT) are technical improvements of morphologic imaging that can evaluate functional properties of hepato-bilio-pancreatic tumors during conventional MRI or CT examinations. Nevertheless, the term “functional imaging” is commonly used to describe molecular imaging techniques, as positron emission tomography (PET) CT/MRI, which still represent the most widely used methods for the evaluation of functional properties of solid neoplasms; unlike PET or single photon emission computed tomography, functional imaging techniques applied to conventional MRI/CT examinations do not require the administration of radiolabeled drugs or specific equipments. Moreover, DWI and DCE-MRI can be performed during the same session, thus providing a comprehensive “one-step” morphological and functional evaluation of hepato-bilio-pancreatic tumors. Literature data reveal that functional imaging techniques could be proposed for the evaluation of these tumors before treatment, given that they may improve staging and predict prognosis or clinical outcome. Microscopic changes within neoplastic tissues induced by treatments can be detected and quantified with functional imaging, therefore these techniques could be used also for post-treatment assessment, even at an early stage. The aim of this editorial is to describe possible applications of new functional imaging techniques apart from molecular imaging to hepatic and pancreatic tumors through a review of up-to-date literature data, with a particular emphasis on pathological correlations, prognostic stratification and post-treatment monitoring.

Dynamic contrast-enhanced magnetic resonance imaging for pancreatic ductal adenocarcinoma at 3.0-T magnetic resonance: correlation with histopathology

PURPOSE

The aim of this study was to discuss the correlation of quantitative dynamic contrast-enhanced magnetic resonance imaging (QDCE-MRI) at 3.0-T magnetic resonance and histopathology for pancreatic ductal adenocarcinoma (PDA).

METHODS

Twenty-three patients with histopathologically proven PDA were included in this study after 75 cases of suspected pancreatic tumors had been performed by QDCE-MRI. The quantitative kinetic parameters analyzed by 2-compartment and 3-compartment models were calculated automatically, which included the volume transfer constant of the contrast agent, the rate constant (Kep), the volume as a percentage of the extravascular extracellular leakage space, the time of arrival of contrast agent, the time of peaking of contrast agent, the maximum slope of signal intensity ascent, and the contrast enhancement ratio. According to magnetic resonance images, tissue section were selected and stained for evaluating tumor differentiation, tumor fibrosis, tumor microvessel density, the expression of tumor vascular endothelial growth factor (VEGF) and Ki67. Subsequently, the relationship between the parameters of QDCE-MRI and histopathology of PDA was analyzed.

RESULTS

The tumor Kep and extravascular extracellular leakage space showed a statistically significant correlation with tumor fibrosis; the tumor volume transfer constant of the contrast agent 2-compartment showed a statistically significant correlation with the expressions of tumor VEGF; and the tumor Kep, maximum slope of signal intensity ascent, and contrast enhancement ratio showed a statistically significant correlation with the expression of tumor Ki67.

CONCLUSIONS

The parameters of QDCE-MRI of PDA can be used to evaluate the degrees of tumor fibrosis and the expressions of VEGF and Ki67.

New challenges in perioperative management of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer-related death in the industrialized world. Despite progress in the understanding of the molecular and genetic basis of this disease, the 5-year survival rate has remained low and usually does not exceed 5%. Only 20%-25% of patients present with potentially resectable disease and surgery represents the only chance for a cure. After decades of gemcitabine hegemony and limited therapeutic options, more active chemotherapies are emerging in advanced PDAC, like 5-Fluorouracil, folinic acid, irinotecan and oxaliplatin and nab-paclitaxel plus gemcitabine, that have profoundly impacted therapeutic possibilities. PDAC is considered a systemic disease because of the high rate of relapse after curative surgery in patients with resectable disease at diagnosis. Neoadjuvant strategies in resectable, borderline resectable, or locally advanced pancreatic cancer may improve outcomes. Incorporation of tissue biomarker testing and imaging techniques into preoperative strategies should allow clinicians to identify patients who may ultimately achieve curative benefit from surgery. This review summarizes current knowledge of adjuvant and neoadjuvant treatment for PDAC and discusses the rationale for moving from adjuvant to preoperative and perioperative therapeutic strategies in the current era of more active chemotherapies and personalized medicine. We also discuss the integration of good specimen collection, tissue biomarkers, and imaging tools into newly designed preoperative and perioperative strategies.

Diffusion tensor magnetic resonance imaging of the pancreas

PURPOSE

To develop a diffusion-tensor-imaging (DTI) protocol that is sensitive to the complex diffusion and perfusion properties of the healthy and malignant pancreas tissues.

MATERIALS AND METHODS

Twenty-eight healthy volunteers and nine patients with pancreatic-ductal-adenocacinoma (PDAC), were scanned at 3T with T2-weighted and DTI sequences. Healthy volunteers were also scanned with multi-b diffusion-weighted-imaging (DWI), whereas a standard clinical protocol complemented the PDAC patients' scans. Image processing at pixel resolution yielded parametric maps of three directional diffusion coefficients λ1, λ2, λ3, apparent diffusion coefficient (ADC), and fractional anisotropy (FA), as well as a λ1-vector map, and a main diffusion-direction map.

RESULTS

DTI measurements of healthy pancreatic tissue at b-values 0,500 s/mm² yielded: λ1 = (2.65±0.35)×10⁻³, λ2 = (1.87±0.22)×10⁻³, λ3 = (1.20±0.18)×10⁻³, ADC = (1.91±0.22)×10⁻³ (all in mm²/s units) and FA = 0.38±0.06. Using b-values of 100,500 s/mm² led to a significant reduction in λ1, λ2, λ3 and ADC (p<.0001) and a significant increase (p<0.0001) in FA. The reduction in the diffusion coefficients suggested a contribution of a fast intra-voxel-incoherent-motion (IVIM) component at b≤100 s/mm², which was confirmed by the multi-b DWI results. In PDACs, λ1, λ2, λ3 and ADC in both 0,500 s/mm² and 100,500 s/mm² b-values sets, as well as the reduction in these diffusion coefficients between the two sets, were significantly lower in comparison to the distal normal pancreatic tissue, suggesting higher cellularity and diminution of the fast-IVIM component in the cancer tissue.

CONCLUSION

DTI using two reference b-values 0 and 100 s/mm² enabled characterization of the water diffusion and anisotropy of the healthy pancreas, taking into account a contribution of IVIM. The reduction in the diffusion coefficients of PDAC, as compared to normal pancreatic tissue, and the smaller change in these coefficients in PDAC when the reference b-value was modified from 0 to 100 s/mm², helped identifying the presence of malignancy.

Perfusion in the tissue surrounding pancreatic cancer and the patient's prognosis

Objective. The objective was to investigate the relationship between prognosis in case of pancreatic cancer and perfusion in tissue surrounding pancreatic cancer using perfusion CT. Methods. We enrolled 17 patients diagnosed with inoperable pancreatic adenocarcinoma. All patients were examined by perfusion CT and then underwent chemotherapy using gemcitabine. The time density curve (TDC) of each CT pixel was analyzed to calculate area under the curve (AUC) and blood flow (BF) using a mathematical algorithm based on the single-compartment model. To measure the AUC and BF of tumor (AUC_T and BF_T) and peritumoral tissue (AUC_PTT and BF_PTT), regions of interest were manually placed on the cancer and in pancreatic tissue within 10 mm of proximal pancreatic parenchyma. Survival days from the date of perfusion CT were recorded. Correlation between AUC or BF and survival days was assessed. Results. We found a significant correlation between AUC_PTT or BF_PTT and survival days (P = 0.04 or 0.0005). Higher AUC_PTT or BF_PTT values were associated with shorter survival. We found no significant correlation between AUC_T or BF_T and survival. Conclusions. Our results suggest that assessments of perfusion in pancreatic tissue within 10 mm of proximal pancreatic parenchyma may be useful in predicting prognosis.

Imaging diagnosis of pancreatic cancer: A state-of-the-art review

Pancreatic cancer (PC) remains one of the deadliest cancers worldwide, and has a poor, five-year survival rate of 5%. Although complete surgical resection is the only curative therapy for pancreatic cancer, less than 20% of newly-diagnosed patients undergo surgical resection with a curative intent. Due to the lack of early symptoms and the tendency of pancreatic adenocarcinoma to invade adjacent structures or to metastasize at an early stage, many patients with pancreatic cancer already have advanced disease at the time of their diagnosis and, therefore, there is a high mortality rate. To improve the patient survival rate, early detection of PC is critical. The diagnosis of PC relies on computed tomography (CT) and/or magnetic resonance imaging (MRI) with magnetic resonance cholangiopancreatography (MRCP), or biopsy or fine-needle aspiration using endoscopic ultrasound (EUS). Although multi-detector row computed tomography currently has a major role in the evaluation of PC, MRI with MRCP facilitates better detection of tumors at an early stage by allowing a comprehensive analysis of the morphological changes of the pancreas parenchyma and pancreatic duct. The diagnosis could be improved using positron emission tomography techniques in special conditions in which CT and EUS are not completely diagnostic. It is essential for clinicians to understand the advantages and disadvantages of the various pancreatic imaging modalities in order to be able to make optimal treatment and management decisions. Our study investigates the current role and innovative techniques of pancreatic imaging focused on the detection of pancreatic cancer.

Quantitative magnetization transfer MRI of desmoplasia in pancreatic ductal adenocarcinoma xenografts

Quantitative assessment of desmoplasia in pancreatic ductal adenocarcinoma (PDAC) may be critical for staging or prediction of response to therapy. We performed quantitative magnetization transfer (qMT) MRI measurements in 18 mouse xenograft tumors generated from three PDAC cell lines. The qMT parameter bound proton fraction (BPF) was found to be significantly higher in tumors grown using the BxPC-3 cell line (5.31 ± 0.87, mean ± standard deviation) compared with the BPF measured for tumors grown from Panc-1 (3.65 ± 0.60) and Capan-1 (1.50 ± 0.58) cell lines (P < 0.05 for each comparison). Histologic measurements demonstrated a similar trend; BxPC-3 tumors had significantly higher fibrosis levels (percentage of fibrotic tissue area, 6.21 ± 2.10) compared with Panc-1 (2.88 ± 1.13) and Capan-1 (1.69 ± 1.01) tumors. BPF was well correlated with quantitative fibrosis levels (r = 0.77, P < 0.01). Our results indicate that qMT measurements offer the potential to noninvasively quantify fibrosis levels in PDAC mouse xenograft models and thus serve as a valuable in vivo biomarker of desmoplasia in PDAC.

Incorporating prognostic imaging biomarkers into clinical practice

A prognostic imaging biomarker can be defined as an imaging characteristic that is objectively measurable and provides information on the likely outcome of the cancer disease in an untreated individual and should be distinguished from predictive imaging biomarkers and imaging markers of response. A range of tumour characteristics of potential prognostic value can be measured using a variety imaging modalities. However, none has currently been adopted into routine clinical practice. This article considers key examples of emerging prognostic imaging biomarkers and proposes an evaluation framework that aims to demonstrate clinical efficacy and so support their introduction into the clinical arena. With appropriate validation within an established evaluation framework, prognostic imaging biomarkers have the potential to contribute to individualized cancer care, in some cases reducing the financial burden of expensive cancer treatments by facilitating their more rational use.

Computed tomography perfusion imaging of renal cell carcinoma: systematic comparison with histopathological angiogenic and prognostic markers

PURPOSE

The aim of this study was to systematically analyze the correlation between computed tomography (CT) perfusion and histopathological angiogenic and prognostic markers in patients with renal cell carcinoma (RCC).

MATERIAL AND METHODS

Fifteen patients (12 men; mean age, 64.5 ± 9.4 years) with RCC underwent contrast-enhanced CT perfusion imaging (scan range, 10 cm; scan time, 40 seconds; dual-source 128-section CT) 1 day before surgery. The procedure for surgical specimen processing was modified to obtain an exact match with CT images. Microvessel density (MVD) was quantified by CD34 staining, and lymphatic vessel density (LVD) was stained with D2-40 antibodies. The CT perfusion values blood flow (BF), blood volume (BV), and flow extraction product (K(Trans)) were calculated using the maximum-slope and a delay-corrected modified Patlak approach and were correlated to MVD and LVD. The relationship between CT perfusion and the prognostic markers pT stage, Fuhrman grade, and tumor necrosis was evaluated.

RESULTS

Histopathology revealed varying high MVD but low or absent intratumoral LVD. The BF and BV of RCC, both including and excluding necrotic regions, showed significant correlations with MVD (r = 0.600-0.829, P < 0.05 each). Significant correlations between MVD and K(Trans) were found only in small tumor areas exhibiting no necrosis (r = 0.550, P < 0.05). No significant correlation was found between BF, BV, and K(Trans) with intratumoral LVD (P = 0.35-0.82). With higher pT stage and Fuhrman grade, BF, BV, and K(Trans) were lower, similar to the MVD, but without reaching statistical significance. Blood flow, BV, and K(Trans) were significantly higher in RCCs with less than 50% necrosis than in those with 50% or grater necrosis (P < 0.05 each).

CONCLUSION

Our study indicates that BF and BV from CT perfusion reflect blood vessels of RCC. Computed tompgraphic perfusion parameters differ significantly depending upon the degree of tumor necrosis.

Pancreatic cancer: why is it so hard to treat?

No common malignancy is as rapidly and inevitably fatal as pancreatic ductal adenocarcinoma (PDA). This grim fact has driven substantial research efforts into this disease in recent decades. Unfortunately, the investment has yet to result in a meaningful increase in 5-year survival. This has prompted many pancreatic cancer researchers and advocates to redouble their efforts, but also requires one to step back and ask why the previous efforts were lacking and to consider why pancreatic cancer is so difficult to treat. The difficulties are legion. PDA is characterized by an insidious clinical syndrome, but is rarely diagnosed at a time when surgical resection is feasible. We lack markers of early detection and screening programs remain unproven even in high risk populations. The location of the tumor in the retroperitoneum, the advanced age of patients, and the systemic effects of disease limit the options for local therapy. Chemotherapy may provide a small benefit, but most efforts to improve on the current regimens consistently and stubbornly fail in advanced clinical trials. The molecular and cellular features of ductal pancreatic tumors are aggressive and underlay multiple levels of therapeutic resistance. Non-cell-autonomous features including stromal proliferation, reduced vascular density and immune suppression also contribute to therapeutic resistance. Growing awareness of these the fundamental features of PDA has begun to guide ongoing research efforts. Clinical trials are now specifically targeting these tumor properties and actively focusing on the therapeutic implications of tumor stroma. As reviewed here, reflecting on the fundamental question of why pancreatic cancer is so difficult to treat is a necessary and informative exercise that will aid our efforts to improve patient outcomes. These efforts will lead to improvements in clinical trial design, expand our focus to include the molecular and histologic implications of novel treatment paradigms, and ultimately change the lives of our patients.

A solid pancreatic mass: tumour or inflammation?

The prognosis for pancreatic cancer is poor, and early diagnosis is essential for surgical management. By comparison with its classic form, the presence of acute or chronic inflammatory signs will hinder its detection and delay its diagnosis. The atypical forms of acute pancreatitis need to be known in order to detect patients who require additional morphological investigations to search for an underlying tumour. In contrast, pseudotumoral forms of inflammation (chronic pancreatitis, cystic dystrophy in heterotopic pancreas, autoimmune pancreatitis) may simulate a cancer, and make up 5-10% of the surgical procedures for suspected cancer. Faced with these pseudotumoral masses, interpretation relies on various differentiating signs and advances in imaging.

Solid pancreatic lesions: characterization by using timing bolus dynamic contrast-enhanced MR imaging assessment--a preliminary study

PURPOSE

To assess the feasibility of postprocessing dynamic contrast material-enhanced (DCE) magnetic resonance (MR) imaging timing bolus data by using a three-dimensional radial gradient-echo technique with k-space-weighted image contrast (KWIC) for the characterization of solid pancreatic diseases.

MATERIALS AND METHODS

This retrospective study was approved by the institutional review board, and informed consent was waived. A total of 45 patients suspected of having biliary or pancreatic disease underwent pancreatic MR examination with a 3.0-T imager with a low-dose (2 mL gadopentetate dimeglumine) timing bolus by using the radial KWIC technique. There were 24 patients with pancreatic cancers, eight with pancreatic neuroendocrine tumors (PNETs), three with chronic pancreatitis, and 10 with a normal pancreas. By using a dedicated postprocessing software program for DCE MR imaging, the following perfusion parameters were measured for tumor and nontumorous parenchyma: volume transfer coefficient (K(trans)) and extracellular extravascular volume fraction; the rate constant (k(ep)) and initial area under the concentration curve in 60 seconds (iAUC) were then generated. The perfusion parameters acquired on DCE MR images were compared among the groups by using the analysis of variance test.

RESULTS

K(trans), k(ep), and iAUC values in patients with pancreatic cancer (0.042 min(-1) ± 0.023 [standard deviation], 0.761 min(-1) ± 0.529, and 2.841 mmol/sec ± 1.811, respectively) were significantly lower than in patients with a normal pancreas (0.387 min(-1) ± 0.176, 6.376 min(-1) ± 2.529, and 7.156 mmol/sec ± 3.414, respectively) (P < .05 for all). In addition, k(ep) values of PNETs and normal pancreas also differed (P < .0001), and K(trans), k(ep), and iAUC values of pancreatic cancers and PNETs differed significantly (P < .0001, P = .038, and P < .0001, respectively).

CONCLUSION

Results of timing bolus DCE MR imaging with the radial KWIC sequence from routine examinations can be postprocessed to yield potentially useful perfusion parameters for the characterization of pancreatic diseases.

Evaluation of pancreatic cancer by multiple breath-hold dynamic contrast-enhanced magnetic resonance imaging at 3.0T

OBJECTIVE

To investigate the microcirculation in pancreatic cancer by pharmacokinetic analysis of multiple breath-hold dynamic contrast-enhanced magnetic resonance imaging at 3.0T.

MATERIALS AND METHODS

Multiple breath-hold dynamic contrast-enhanced magnetic resonance imaging was performed in 40 healthy volunteers and 40 patients with pancreatic cancer proven by histopathology using an axial three-dimensions fat-saturated T1-weighted spoiled-gradient echo sequence at 3.0T. A two compartment model with T1 correction was used to quantify the transfer constant, the rate constant of backflux from the extravascular extracellular space to the plasma and the extravascular extracellular space fractional volume in pancreatic cancer, obstructive pancreatitis distal to the malignant tumor, adjacent pancreatic tissue proximal to the tumor and normal pancreas. All parameters were statistically analyzed.

RESULTS

Statistical differences were noticed in both the transfer constant (p=0.000075) and the rate constant of backflux (p=0.006) among different tissues. Both the transfer constant and the rate constant of backflux in pancreatic cancer were statistically lower than those in normal pancreas and adjacent pancreatic tissue (p<0.05). Both the transfer constant and the rate constant of backflux in obstructive pancreatitis were statistically lower than those in normal pancreas and adjacent pancreatic tissue (p<0.05). The extravascular extracellular space fractional volume in pancreatic cancer was statistically lager than that in normal pancreas (p=0.002).

CONCLUSION

Multiple breath-hold dynamic contrast-enhanced magnetic resonance imaging offers a useful technique to evaluate the microenvironment in pancreatic cancer at 3.0T. Compared to normal pancreas, pancreatic cancer has lower transfer constant, rate constant of backflux and larger extravascular extracellular space fractional volume.

Magnetization transfer MRI in pancreatic cancer xenograft models

Magnetization transfer magnetic resonance imaging measurements were performed in three pancreatic ductal adenocarcinoma mouse xenograft models. For each of 28 pancreatic ductal adenocarcinoma xenografts, MT ratios (MTRs) were calculated and compared to histologic fibrosis levels from reference standard trichrome staining. MTR was found to be significantly higher in tumors grown using BxPC-3 cell line (39.4±5.1, mean±SD) compared to the MTR for the tumors grown from Panc-1 (32.4±2.8) and Capan-1 (27.3±2.9) cell lines (P<0.05 for each comparison). Histologic measurements showed a similar trend with BxPC-3 tumors demonstrating significantly higher fibrosis levels (percentage of fibrotic tissue area, 6.48±2.59) when compared to Panc-1 (3.54±2.18) and Capan-1 (2.07±1.60) tumors. MTR measurements were well correlated to quantitative fibrosis levels (r=0.69, P=0.01). Results indicated that MTR measurements offer the potential to serve as a valuable in vivo biomarker of desmoplasia in pancreatic ductal adenocarcinoma.