Update of PET and PET/CT for hepatobiliary and pancreatic malignancies

Predictive value of metabolic activity detected by pre-operative 18F FDG PET/CT in ampullary adenocarcinoma

In ampullary adenocarcinoma cases, the clinical effects of 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) have not yet been well-studied, unlike other prognostic factors that have been reported till date. This study aimed to investigate the clinical impact of maximum standardized uptake value (SUVmax) in predicting the prognosis of ampullary adenocarcinoma.Thirty-eight patients who underwent pre-operative 18F-FDG PET/CT and curative-intent resection of ampullary adenocarcinoma at Pusan National University Hospital (Pusan, South Korea) between 2008 and 2017 were retrospectively analyzed in this study. We evaluated the clinicopathologic outcomes according to the SUVmax using univariate and multivariate Cox proportional hazard regression analyses and receiver operating characteristic analysis to arrive at a cutoff value.Lymph node metastasis was detected in 9 patients, and 15 patients experienced a recurrence during the follow-up period. Among 38 patients, 33 showed an increased FDG uptake by the main tumor. SUVmax of 4.55 was selected as a significant independent predictive factor for patient survival along with poor tumor differentiation and high neutrophil-to-lymphocyte ratio in multivariate analysis (P = .016, hazard ratio = 5.040). Patients with SUVmax under 4.55 exhibited significantly longer overall survival than the rest (<4.55 vs ≥4.55), and the 5-year overall survival was 82.8% versus 57.4% (P = .049).SUVmax of 4.55 on 18F-FDG PET/CT could be a predictive factor for tumor biology and long-term survival in patients with ampullary adenocarcinoma. Nevertheless, considering the cost aspect and its limited prognostic effect, this study seems to require more patient and multicenter studies.

Positron Emission Tomography Combined With Computed Tomography vs. No Positron Emission Tomography Combined With Computed Tomography for the Management of Patients With Resectable Colorectal Cancer Liver Metastases and Synchronous Extrahepatic Disease

INTRODUCTION

Selected patients with colorectal cancer liver metastases (CRLM) and synchronous extrahepatic disease (EHD) are considered for surgery.

OBJECTIVES

To evaluate the change in surgical management and long-term survival (disease-free survival [DFS] and overall survival [OS]) for patients with CRLM and EHD who undergo positron emission tomography combined with computed tomography (PET-CT) vs no PET-CT.

METHODS

Patients with CRLM were enrolled in a trial evaluating the effect of PET-CT (vs no PET-CT) on surgical management, DFS, and OS. This is a sub-study of the trial, including only patients with synchronous EHD. Cox proportional hazard models were used to calculate risks for recurrence and death. Survival were described by Kaplan-Meier method and compared with log-rank test.

RESULTS

Of 25 patients with EHD (PET-CT arm: 14/270 (5%) and no PET-CT arm: 11/134 (8%)), PET-CT changed surgical management in 14%, all of which avoided liver resection due to more extensive disease. Complete metastasectomy was achieved in 36% (5/14) and 72% (8/11), respectively. Respectively, PET-CT vs no PET-CT had statistically similar median DFS, 5.6 months (95% confidence interval (CI) 3.6-18) vs 7.6 months (95% CI 2.9-15) and median OS, 42 months (95% CI 25-48) vs 29 months (95% CI 17-41). EHD was associated with worse DFS (hazard ratio HR = 1.89, 95% CI 1.41-2.52) and OS (HR = 2.47, 95% CI 1.6-3.83).

CONCLUSIONS

Preoperative PET-CT for the management of resectable CRLM did not improve long-term outcomes among patients who had synchronous EHD; however, it changed surgical management in a relatively significant proportion of patients.

Groove Pancreatitis Associated with Transient Liver Injury Mimicking Ampullary Neoplasm

Groove pancreatitis is an unusual form of pancreatitis characterized by fibrous inflammation and pseudo-tumor in the area around the head of the pancreas. The underlying etiology is unknown but is strongly linked to alcohol abuse. We report a 52-year-old male smoker with hypertension, asthma, and alcohol abuse who was admitted with severe epigastric pain radiating to the back. He was found to have acute pancreatitis. A computed tomography scan of the abdomen showed a mass lesion in the peri-ampullary region. MRI of the abdomen revealed dilated common bile duct and duodenal mass and features suggestive of groove pancreatitis. During the hospital stay, bilirubin and liver enzymes started to rise and then decreased gradually to the previous normal range. The secondary workup for liver disease was unremarkable. The patient improved and was discharged. Six-month follow-up showed regression of the duodenal lesion and reduction in the common bile duct dilatation. Excluding malignancy remains the main challenge in managing groove pancreatitis, and a conservative approach is more reasonable in cases with a typical profile.

Role of Radiological Imaging in the Diagnosis and Characterization of Pancreatic Cystic Lesions: A Systematic Review

The evidence on the ability of radiological tests to predict a specific diagnosis and also their aptitude in identifying pathological markers indicative of malignancy in cystic lesions of the pancreas remains inconclusive. We conducted a systematic review on MEDLINE for the use of computed tomography (CT), magnetic resonance imaging, and positron emission tomography/CT (PET/CT) in the diagnosis and characterization of these cysts. The accuracy of CT scan for reaching a specific diagnosis was 39% to 61.4%, whereas its accuracy for differentiating benign from malignant lesions was 61.9% to 80%. Magnetic resonance imaging showed a better accuracy in identifying a specific diagnosis of 50% to 86%, whereas its accuracy in differentiating benign from malignant lesions was 55.6% to 87%. The use of magnetic resonance imaging was superior to CT scan in identifying septations, mural nodules, and ductal communication. The sensitivity of PET/CT in diagnosing malignancy was 85.7% to 100% with a reported accuracy of 88% to 95%. The evidence gathered from this review suggests that the adequacy of CT imaging in full characterization of pancreatic cysts is suboptimal, and therefore a low threshold for supplementary imaging is advised. The use of PET/CT should be considered in high-risk patients with equivocal findings.

Incremental Role of Fluorine 18-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in the Assessment of Computed Tomography-Inconspicuous Pancreatic Lesions

Background: Pancreatic malignancies encompass a heterogenous group of disorders, with poor prognosis at diagnosis. Traditionally, conventional computed tomography (CT) has been used for diagnosis, staging, and follow up. However, this technique lacks functional information; and is limited in diagnosis of occult pancreatic disease. Hybrid imaging in the form of positron emission tomography (PET)/CT provides a potential avenue for early detection and subsequent appropriate therapy.

Case Presentation: A 60-year-old male, with a history of abdominal aortic aneurysm which was repaired, came with a complaint of 2 months history of back pain, radiating to the front. The pain was relieved on leaning forward, and aggravated by lying on his back. CT angiography of the abdomen was done, which revealed a concealed aortic aneurysm and a significant atrophy of the pancreatic tail. The serum cancer antigen (CA) 19-9 was elevated (50.0 U/mL, reference range 0.0–37.0 U/mL). At this juncture, the PET scan done revealed no discernible abnormalities. Patient was put on close follow-up in view of the rising trend of CA 19-9 levels. Three months following the initial scans, a repeat ¹⁸F-FDG (fluorine 18 fluorodeoxyglucose) PET/CT revealed an FDG-avid lesion at the neck of the pancreas on PET without perceptible changes on the correlated CT. A Whipple's procedure ensued, with histopathological examination findings of pancreatic adenocarcinoma.

Conclusion: This article discusses the role of PET/CT in the early diagnosis of inconspicuous pancreatic lesions; which could have averted immediate medical therapy.

2-[(18)F]fluoro-2-deoxy-D-galactose PET/CT of hepatocellular carcinoma is not improved by co-administration of galactose

INTRODUCTION

PET with [(18)F]fluoro-2-deoxy-D-galactose ((18)F-FDGal) is a promising imaging modality for detection of hepatocellular carcinoma (HCC). However, it can be difficult to distinguish small intrahepatic HCC lesions from surrounding liver tissue. Ut the competitive inhibition that galactose shows towards hepatic (18)F-FDGal metabolism, we tested the hypothesis that co-administration of galactose, at near-saturating doses, inhibits (18)F-FDGal metabolism to a greater extent in non-malignant hepatocytes than in HCC cells. This would increase the tumor to background ratio in the (18)F-FDGal PET scans with co-administration of galactose.

METHODS

Three patients known to have HCC underwent two (18)F-FDGal PET/CT scans on consecutive days, one with and one without simultaneous constant intravenous infusion of galactose. On both days, (18)F-FDGal was injected in the beginning of a 45-min dynamic PET scan of the liver followed by a static PET scan from mid-thigh to the top of the skull starting 60-70min after (18)F-FDGal administration. Parametric images of the hepatic metabolic function expressed in terms of hepatic systemic clearance of (18)F-FDGal were generated from the dynamic PET recordings.

RESULTS

Co-administration of galactose did not give significantly better discrimination of the HCC lesions from background. Parametric images of the hepatic metabolic function did not add additional useful information to the detection of HCC lesions compared to the static images of radioactivity concentrations.

CONCLUSION

Co-administration of galactose did not improve the interpretation of the (18)F-FDGal PET/CT images and did not improve the detection of intrahepatic HCC lesions, either using static or parametric images.

Optimal 2-[(18)F]fluoro-2-deoxy-D-galactose PET/CT protocol for detection of hepatocellular carcinoma

BACKGROUND

Positron emission tomography (PET) with the liver-specific galactose tracer 2-[(18)F]fluoro-2-deoxy-D-galactose ((18)F-FDGal) may improve diagnosis of hepatocellular carcinoma (HCC). The aim of this study was to test which of three different (18)F-FDGal PET protocols gives the highest tumour-to-background (T/B) ratio on PET images and thus better detection of HCC tumours.

METHODS

Ten patients with a total of 15 hepatic HCC tumours were enrolled prior to treatment. An experienced radiologist defined volumes of interest (VOIs) encircling HCC tumours on contrast-enhanced CT (ce-CT) images. Three PET/CT protocols were conducted following an intravenous (18)F-FDGal injection: (i) a 20-min dynamic PET/CT of the liver (to generate a 3D metabolic image), (ii) a traditional static whole-body PET/CT after 1 h, and (iii) a late static whole-body PET/CT after 2 or 3 h. PET images from each PET/CT protocol were fused with ce-CT images, and the average standardized uptake values (SUV) in tumour and background liver tissue were used to calculate (T/B) ratios. Furthermore, Tpeak/B ratios were calculated using the five hottest voxels in all hot tumours. The ratios for the three different PET protocols were compared.

RESULTS

For the individual tumours, there was no significant difference in the T/B ratio between the three PET protocols. The metabolic image yielded higher Tpeak/B ratios than the two static images, but it was easier to identify tumours on the static images. One extrahepatic metastasis was detected.

CONCLUSIONS

Neither metabolic images nor static whole-body images acquired 2 or 3 h after (18)F-FDGal injection offered an advantage to traditional whole-body PET/CT images acquired after 1 h for detection of HCC.

Advances in computed tomography and magnetic resonance imaging of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common primary liver cancer. Imaging is important for establishing a diagnosis of HCC and early diagnosis is imperative as several potentially curative treatments are available when HCC is small. Hepatocarcinogenesis occurs in a stepwise manner on a background of chronic liver disease or cirrhosis wherein multiple genes are altered resulting in a range of cirrhosis-associated nodules. This progression is related to increased cellularity, neovascularity and size of the nodule. An understanding of the stepwise progression may aid in early diagnosis. Dynamic and multiphase contrast-enhanced computed tomography and magnetic resonance imaging still form the cornerstone in the diagnosis of HCC. An overview of the current diagnostic standards of HCC in accordance to the more common practicing guidelines and their differences will be reviewed. Ancillary features contribute to diagnostic confidence and has been incorporated into the more recent Liver Imaging Reporting and Data System. The use of hepatocyte-specific contrast agents is increasing and gradually changing the standard of diagnosis of HCC; the most significant benefit being the lack of uptake in the hepatocyte phase in the earlier stages of HCC progression. An outline of supplementary techniques in the imaging of HCC will also be reviewed.

CT Findings of Patients Treated with Irreversible Electroporation for Locally Advanced Pancreatic Cancer

Introduction. In patients with locally advanced pancreatic cancer (LAPC), IRE has been shown to be safe for local disease control and palliation. As IRE continues to gain acceptance it is important to characterize the expected imaging findings. Materials and Methods. A review of our prospective soft tissue ablation registry from July 2010 to June 2013 was performed on patients who had undergone IRE for LAPC. Five masses treated with intraoperative IRE ablation for pancreatic tumors that underwent CT imaging before and after ablation were reviewed. Results and Discussion. Following IRE, the postablation bed is larger than the original ablated tumor. This ablation zone may get smaller in size (due to decreased edema and hyperemia) in the following months and more importantly remains stable provided there is no recurrence. In cases of recurrent disease there is increased size of the ablation bed, mass effect, and new or worsening vascular encasement or occlusion. Conclusion. CT imaging remains the best current imaging modality to assess post-IRE ablation changes. Serial imaging over at least 2-6 months must be employed to detect recurrence by comparing with prior studies in conjunction with clinical and serum studies. Larger imaging studies are underway to evaluate a more ideal imaging modality for this unique patient population.

Potential role of FDG PET/CT in evaluating patients with hepatic incidentalomas

This review article is focused on the role of FDG PET/CT in diagnosing and characterizing hepatic incidentalomas. A large variety of unsuspected lesions can be detected in the liver both with ultrasound and CT performed for other reasons; the prevalence of liver incidentalomas increases in patients with chronic liver disease or preexisting oncologic history. The major challenge is to discriminate benign from malignant lesions. There is a large body of literature indicating that FDG PET/CT is a useful tool to this purpose even if it is unspecific (ie, it cannot differentiate a primary tumor from a secondary lesion). Occasionally, FDG PET/CT can be useful for biopsy guidance.

FDG-PET/CT-based restaging may alter initial management decisions and clinical outcomes in patients with locally advanced pancreatic carcinoma planned to undergo chemoradiotherapy

The impact of [(18)F]fluorodeoxyglucose-positron emission tomography (PET)/computed tomography (CT) restaging on management decisions and outcomes in patients with locally advanced pancreatic carcinoma (LAPC) scheduled for concurrent chemoradiotherapy (CRT) is examined. Seventy-one consecutive patients with conventionally staged LAPC were restaged with PET/CT before CRT, and were categorized into non-metastatic (M0) and metastatic (M1) groups. M0 patients received 50.4 Gy CRT with 5-fluorouracil followed by maintenance gemcitabine, whereas M1 patients received chemotherapy immediately or after palliative radiotherapy. In 19 patients (26.8%), PET/CT restaging showed distant metastases not detected by conventional staging. PET/CT restaging of M0 patients showed additional regional lymph nodes in 3 patients and tumors larger than CT-defined borders in 4. PET/CT therefore altered or revised initial management decisions in 26 (36.6%) patients. At median follow-up times of 11.3, 14.5, and 6.2 months for the entire cohort and the M0 and M1 cohorts, respectively, median overall survival was 16.1, 11.4, and 6.2 months, respectively; median locoregional progression-free survival was 9.9, 7.8, and 3.4 months, respectively; and median progression-free survival was 7.4, 5.1, and 2.5 months, respectively (P < 0.05 each). These findings suggest that PET/CT-based restaging may help select patients suitable for CRT, sparing those with metastases from futile radical protocols, and increasing the accuracy of estimated survival.

Consistent surgeon evaluations of three-dimensional rendering of PET/CT scans of the abdomen of a patient with a ductal pancreatic mass

Two-dimensional (2D) positron emission tomography (PET) and computed tomography (CT) are used for diagnosis and evaluation of cancer patients, requiring surgeons to look through multiple planar images to comprehend the tumor and surrounding tissues. We hypothesized that experienced surgeons would consistently evaluate three-dimensional (3D) presentation of CT images overlaid with PET images when preparing for a procedure. We recruited six Jefferson surgeons to evaluate the accuracy, usefulness, and applicability of 3D renderings of the organs surrounding a malignant pancreas prior to surgery. PET/CT and contrast-enhanced CT abdominal scans of a patient with a ductal pancreatic mass were segmented into 3D surface renderings, followed by co-registration. Version A used only the PET/CT image, while version B used the contrast-enhanced CT scans co-registered with the PET images. The six surgeons answered 15 questions covering a) the ease of use and accuracy of models, b) how these models, with/without PET, changed their understanding of the tumor, and c) what are the best applications of the 3D visualization, on a scale of 1 to 5. The six evaluations revealed a statistically significant improvement from version A (score 3.6±0.5) to version B (score 4.4±0.4). A paired-samples t-test yielded t(14) = -8.964, p<0.001. Across the surgeon cohort, contrast-enhanced CT fused with PET provided a more lifelike presentation than standard CT, increasing the usefulness of the presentation. The experienced surgeons consistently reported positive reactions to 3D surface renderings of fused PET and contrast-enhanced CT scans of a pancreatic cancer and surrounding organs. Thus, the 3D presentation could be a useful preparative tool for surgeons prior to making the first incision. This result supports proceeding to a larger surgeon cohort, viewing prospective 3D images from multiple types of cancer.

Imaging of hepatocellular carcinoma: diagnosis, staging and treatment monitoring

Hepatocellular carcinoma (HCC) is the most common primary liver cancer. Imaging is important for establishing a diagnosis of HCC. Several imaging modalities including ultrasonography (US), computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET) and angiography are used in evaluating patients with chronic liver disease and suspected HCC. CT, MRI and contrast-enhanced US have replaced biopsy for diagnosis of HCC. Dynamic multiphase contrast-enhanced CT or MRI is the current standard for imaging diagnosis of HCC. Functional imaging techniques such as perfusion CT and diffusion-weighted MRI provide additional information about tumor angiogenesis that may be useful for treatment. Techniques evaluating tissue mechanical properties such as magnetic resonance elastography, and acoustic radiation force impulse imaging are being explored for characterizing liver lesions. The role of PET in the evaluation of HCC is evolving with promise seen especially with the use of a hepatocyte-specific PET tracer. Imaging is also critical for assessment of treatment response and detection of recurrence following locoregional treatment. Knowledge of the post-treatment appearance of HCC is essential for correct interpretation. This review article provides an overview of the role of imaging in the diagnosis, staging and post-treatment follow-up of HCC.

First clinical experience with integrated whole-body PET/MR: comparison to PET/CT in patients with oncologic diagnoses

The recently introduced first integrated whole-body PET/MR scanner allows simultaneous acquisition of PET and MRI data in humans and, thus, may offer new opportunities, particularly regarding diagnostics in oncology. This scanner features major technologic differences from conventional PET/CT devices, including the replacement of photomultipliers with avalanche photodiodes and the need for MRI-based attenuation correction. The aim of this study was to evaluate the comparability of clinical performance between conventional PET/CT and PET/MR in patients with oncologic diseases.

METHODS

Thirty-two patients with different oncologic diagnoses underwent a single-injection, dual-imaging protocol consisting of a PET/CT and subsequent PET/MR scan. PET/CT scans were performed according to standard clinical protocols (86 ± 8 min after injection of 401 ± 42 MBq of (18)F-FDG, 2 min/bed position). Subsequently (140 ± 24 min after injection), PET/MR was performed (4 min/bed position). PET images of both modalities were reconstructed iteratively. Attenuation and scatter correction as well as regional allocation of PET findings were performed using low-dose CT data for PET/CT and Dixon MRI sequences for PET/MR. PET/MR and PET/CT were compared visually by 2 teams of observers by rating the number and location of lesions suspicious for malignancy, as well as image quality and alignment. For quantitative comparison, standardized uptake values (SUVs) of the detected lesions and of different tissue types were assessed.

RESULTS

Simultaneous PET/MR acquisition was feasible with high quality in short acquisition time (≤ 20 min). No significant difference was found between the numbers of suspicious lesions (n = 80) or lesion-positive patients (n = 20) detected with PET/MR or PET/CT. Anatomic allocation of PET/MR findings by means of the Dixon MRI sequence was comparable to allocation of PET/CT findings by means of low-dose CT. Quantitative evaluation revealed a high correlation between mean SUVs measured with PET/MR and PET/CT in lesions (ρ = 0.93) and background tissue (ρ = 0.92).

CONCLUSION

This study demonstrates, for what is to our knowledge the first time, that integrated whole-body PET/MR is feasible in a clinical setting with high quality and in a short examination time. The reliability of PET/MR was comparable to that of PET/CT in allowing the detection of hypermetabolic lesions suspicious for malignancy in patients with oncologic diagnoses. Despite different attenuation correction approaches, tracer uptake in lesions and background correlated well between PET/MR and PET/CT. The Dixon MRI sequences acquired for attenuation correction were found useful for anatomic allocation of PET findings obtained by PET/MR in the entire body. These encouraging results may form the foundation for future studies aiming to define the added value of PET/MR over PET/CT.

The potential use of 2-[¹⁸F]fluoro-2-deoxy-D-galactose as a PET/CT tracer for detection of hepatocellular carcinoma

PURPOSE

The aim of the study was to evaluate the feasibility of using the hepatocyte-specific positron emission tomography (PET) tracer 2-[(18)F]fluoro-2-deoxy-D-galactose (FDGal) as a tracer for hepatocellular carcinoma (HCC).

METHODS

In addition to standard clinical investigations, 39 patients with known HCC or suspected of having HCC underwent a partial-body FDGal PET/CT (from base of skull to mid-thigh). Diagnosis of HCC was based on internationally approved criteria. FDGal PET/CT images were analysed for areas with high (hot spots) or low (cold spots) tracer accumulation when compared to surrounding tissue.

RESULTS

Seven patients did not have HCC and FDGal PET/CT was negative in each of them. Twenty-three patients had HCC and were included before treatment. FDGal PET/CT correctly identified 22 of these patients, which was comparable to contrast-enhanced CT. Interestingly, FDGal PET/CT was conclusive in 12 patients in whom conventional imaging techniques were inconclusive and required additional diagnostic investigations or close follow-up. Nine patients were included after treatment of HCC and in these patients FDGal PET/CT was able to distinguish between viable tumour tissue as hot spots and areas with low metabolic activity as cold spots. FDGal PET/CT detected extrahepatic disease in nine patients which was a novel finding in eight patients.

CONCLUSION

FDGal PET/CT has great clinical potential as a PET tracer for detection of extra- but also intrahepatic HCC. In the present study, the specificity of FDGal PET/CT was 100%, which is very promising but needs to be confirmed in a larger, prospective study.

Pretreatment assessment of hepatocellular carcinoma: expert consensus statement

Staging of hepatocellular carcinoma (HCC) is complex and relies on multiple factors including tumor extent and hepatic function. No single staging system is applicable to all patients with HCC. The staging of the American Joint Committee on Cancer / International Union for Cancer Control should be used to predict outcome following resection or liver transplantation. The Barcelona Clinic Liver Cancer scheme is appropriate in patients with advanced HCC not candidate for surgery. Dual phase computed tomography or magnetic resonance imaging can be used for pretreatment assessment of tumor extent but the accuracy of these methods remains poor to characterize < 1 cm lesions. Assessment of tumor response should not rely only on tumor size and new imaging methods are available to evaluate response to therapy in HCC patients. Liver volumetry is part of the preoperative assessment of patients with HCC candidate for resection as it reflects liver function. Preoperative portal vein embolization is indicated in patients with small future liver remnant (≤ 20% in normal liver; ≤ 40% in fibrotic or cirrhotic liver). Tumor size is not a contraindication to liver resection. Liver resection can be proposed in selected patients with multifocal HCC. Besides tumor extent, surgical resection of HCC may be performed in selected patients with chronic liver disease.