Whole-body MRI at 1.5 T and 3 T compared with FDG-PET-CT for the detection of tumour recurrence in patients with colorectal cancer

Imaging in the era of risk-adapted treatment in colon cancer

The treatment landscape for patients with colon cancer is continuously evolving. Risk-adapted treatment strategies, including neoadjuvant chemotherapy and immunotherapy, are slowly finding their way into clinical practice and guidelines. Radiologists are pivotal in guiding clinicians toward the most optimal treatment for each colon cancer patient. This review provides an overview of recent and upcoming advances in the diagnostic management of colon cancer and the radiologist's role in the multidisciplinary approach to treating colon cancer.

Brain Metastases from Colorectal Cancer: A Systematic Review of the Literature and Meta-Analysis to Establish a Guideline for Daily Treatment

Colorectal cancer (CRC) is the third most common malignancy worldwide. Most patients with metastatic CRC develop liver or lung metastases, while a minority suffer from brain metastases. There is little information available regarding the presentation, treatment, and overall survival of brain metastases (BM) from CRC. This systematic review and meta-analysis includes data collected from three major databases (PubMed, Cochrane, and Embase) based on the key words "brain", "metastas*", "tumor", "colorectal", "cancer", and "malignancy". In total, 1318 articles were identified in the search and 86 studies matched the inclusion criteria. The incidence of BM varied between 0.1% and 11.5%. Most patients developed metastases at other sites prior to developing BM. Lung metastases and KRAS mutations were described as risk factors for additional BM. Patients with BM suffered from various symptoms, but up to 96.8% of BM patients were asymptomatic at the time of BM diagnosis. Median survival time ranged from 2 to 9.6 months, and overall survival (OS) increased up to 41.1 months in patients on a multimodal therapy regimen. Several factors including age, blood levels of carcinoembryonic antigen (CEA), multiple metastases sites, number of brain lesions, and presence of the KRAS mutation were predictors of OS. For BM diagnosis, MRI was considered to be state of the art. Treatment consisted of a combination of surgery, radiation, or systemic treatment.

Whole-body magnetic resonance imaging (WB-MRI) in oncology: an Italian survey

PURPOSE

To perform a survey among all members of the Italian Society of Medical and Interventional Radiology (SIRM) to assess how whole-body MRI (WB-MRI) is performed in oncologic patients in Italy.

METHODS

On March 2019, we administered an online poll to all SIRM members about their use of WB-MRI in 2018 asking 15 questions regarding oncologic indications, imaging protocol, use of contrast media, experience in WB-MRI, duration of scan time and reporting time.

RESULTS

Forty-eight members participated to the survey. WB-MRIs/total MRIs ratio was 1%. Lymphoma was the most common indication (17/48, 35%), followed by myeloma and prostate cancer, with these three tumors representing the most common indication in 39/48 of cases (81%). WB-MRI acquisition time and reporting time were 46-60 min in 22/48 centers (46%) and 20-30 min in 19/48 (40%), respectively. WB-MRIs were mostly performed in 1.5T scanners (43/48, 90%), with surface coils (22/48, 46%) being preferred to Q-body (15/48, 31%) and integrated coils (11/48, 23%). Contrast media were injected in 22/48 of the centers (46%), mainly used for breast cancer (13/22, 59%). DWI was the most used sequence (45/48, 94%), mostly with b800 (27/48, 56%), b0 (24/48, 50%) and b1000 (20/48, 42%) values. In about half of cases, radiologists started evaluating WB-MRI non-contrast morphologic sequences, then checking DWI and post-contrast images.

CONCLUSION

WB-MRI was mainly performed at 1.5T unit, with lymphoma, myeloma and prostate cancer having been the most common indications. The extreme variability in the choice of imaging protocols and use of contrast agents demonstrates the need of a standardization of WB-MRI application in clinical practice.

Whole-body MRI added to gadoxetic acid-enhanced liver MRI for detection of extrahepatic disease in patients considered eligible for hepatic resection and/or local ablation of colorectal cancer liver metastases

Background

Fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) can detect extrahepatic disease before local treatment of colorectal liver metastases.

Purpose

To investigate if whole-body magnetic resonance imaging (MRI) added to gadoxetic acid liver MRI could replace FDG-PET/CT for detection of extrahepatic disease in patients with colorectal liver metastases eligible for hepatic local treatment.

Material and Methods

This health-research-ethics-committee-approved prospective consecutive diagnostic accuracy study with written informed consent analyzed 79 cases included between 29 June 2015 and 7 February 2017. Whole-body MRI covering the thorax, abdomen, and pelvis and FDG-PET/CT including contrast-enhanced CT was performed 0–3 days before local treatment of liver metastases. Whole-body MR images were read independently by two readers. FDG-PET/CT images were read independently by two pairs of readers. Histopathology and follow-up imaging were used as reference standard. Sensitivities and specificities were calculated and compared including noninferiority analysis.

Results

Seventy-five malignant lesions and 419 benign lesions were confirmed. Sensitivities of both PET/CT reader pairs 1 and 2 (56.7 and 67.9%) and MRI reader 2 (63.0%) were significantly higher than that of MRI reader 1 (42.7) (P<0.04). Specificities of both PET/CT reader pairs 1 and 2 (92.5 and 92.4%) and MRI reader 1 (91.1%) were significantly higher than that of MRI reader 2 (86.3%) ( P < 0.02). Sensitivity of MRI reader 2 was non-inferior compared to PET/CT reader pair 1. Specificities of both MRI readers were non-inferior to both PET/CT reader pairs.

Conclusion

For detection of extrahepatic disease in patients with colorectal liver metastases, whole-body MRI was non-inferior to FDG-PET/CT for some reader combinations. However, reader-independent non-inferiority could not be demonstrated.

Development and Validation of a Prediction Model for Organ-Specific Recurrences After Curative Resection of Colon Cancer

BACKGROUND

Early detection of postoperative recurrence is beneficial for patients with cancer; however, optimal surveillance remains an issue. To optimize the follow-up plan, the estimation of an individual patient's risk of recurrence is indispensable.

OBJECTIVE

This study aimed to establish a statistical model for predicting the risk of organ-specific recurrence after curative resection of colon cancer.

DESIGN

This was a retrospective cohort study at a tertiary referral hospital.

SETTINGS

This study included 1720 patients with colon cancer treated at the University of Tokyo Hospital between 1997 and 2015. Data were retrospectively retrieved from patient medical charts. The risk score was developed using a competing risk model in a derivation cohort (973 patients treated in 1997-2009) and then validated in a validation cohort (747 patients treated in 2010-2015).

PATIENTS

Patients who underwent curative resection for stage I to III colon cancer were included.

MAIN OUTCOME MEASURES

The prediction of the incidence of postoperative liver and lung metastasis of colon cancer was measured.

RESULTS

The factors selected for the prediction model for liver metastasis included differentiation, T category, venous invasion, N category, and preoperative CEA level. The model for lung metastasis included sex, lymphatic invasion, venous invasion, N category, preoperative CEA level, and malignant bowel obstruction. During external validation, the area under the curve at 60 months was 0.78 (95% CI, 0.71-0.84) for liver metastasis and 0.72 (95% CI, 0.64-0.81) for lung metastasis.

LIMITATIONS

The generalizability of the model to different healthcare settings remains to be elucidated.

CONCLUSIONS

We developed a prediction model to estimate the risk of recurrence in the liver and lung after curative resection of colon cancer, which demonstrated good discrimination ability in the external validation cohort. Our model can aid clinicians and patients in customizing postoperative surveillance according to an individual patient's risk of organ-specific recurrence. See Video Abstract at http://links.lww.com/DCR/A977. DESARROLLO Y VALIDACIÓN DE UN MODELO DE PREDICCIÓN PARA RECURRENCIAS ESPECÍFICAS DESPUÉS DE RESECCIÓN CURATIVA DE UN CÁNCER DE COLON: La detección temprana de una recidiva postoperatoria es beneficiosa para los pacientes afectados de cáncer. Sin embargo, la mejor vigilancia sigue siendo un problema. Para optimizar el plan de seguimiento, la estimación del riesgo individual de recurrencia de un paciente es indispensable.

OBJETIVO

Establecer un modelo estadístico para predecir el riesgo de recurrencia en un organo específico luego de la resección curativa de un cáncer de colon. DISEÑO:: Estudio retrospectivo de cohortes en un hospital de referencia terciaria.

AJUSTES

Este estudio incluyó 1720 pacientes con cáncer de colon tratados en el Hospital de la Universidad de Tokio entre 1997 y 2015. Los datos se recuperaron retrospectivamente de las historias clinicas de los pacientes. La puntuación de riesgo fué desarrollada utilizando un modelo de riesgo competitivo en cohortes de derivación (973 pacientes tratados en 1997-2009) y luego se lo validó en cohortes de validación (747 pacientes tratados en 2010-2015).

PACIENTES

Todos aquellos casos que se sometieron a una resección curativa de cáncer de colon en estadio I-III RESULTADOS PRINCIPLES:: La predicción de la incidencia de metástasis hepáticas y pulmonares postoperatorias del cáncer de colon.

RESULTADOS

Los factores seleccionados para el modelo de predicción de metástasis hepáticas incluyeron diferenciación tumoral, categoría T, invasión venosa, categoría N y nivel de antígeno carcinoembrionario preoperatorio. El modelo de predicción de metástasis pulmonar incluyó el sexo del paciente, la invasión linfática, la invasión venosa, la categoría N, el nivel de antígeno carcinoembrionario preoperatorio y la obstrucción intestinal maligna. Durante la validación externa, el área inferior de la curva a 60 meses fue de 0,78 (intervalo de confianza del 95%: 0,71 a 0,84) para las metástasis hepáticas y de 0,72 (intervalo de confianza del 95%: 0,64 a 0,81) para las metástasis pulmonares.

LIMITACIONES

La generalización del presente modelo a diferentes entornos de atención en salud aún no ha podido ser dilucidado.

CONCLUSIONES

Desarrollamos un modelo de predicción para estimar el riesgo de recurrencia en el hígado y el pulmón después de resección curativa de cáncer de colon, éste modelo demostró una buena capacidad de discriminación en las cohortes de validación externa. El modelo puede ayudar a médicos y pacientes a personalizar la vigilancia postoperatoria de acuerdo con el riesgo individual de recurrencia específica en un órgano específico. Vea el Resumen del Video en http://links.lww.com/DCR/A977.

Current Challenges in Diagnosis and Assessment of the Response of Locally Advanced and Metastatic Renal Cell Carcinoma

Locally advanced and metastatic renal cell carcinoma (RCC) present a specific set of challenges to the radiologist. The detection of metastatic disease is confounded by the ability of RCC to metastasize to virtually any part of the human body long after surgical resection of the primary tumor. This includes sites not commonly included in routine surveillance, which come to light after the patient becomes symptomatic. In the assessment of treatment response, the phenomenon of tumor heterogeneity, where clone selection through systemic therapy drives the growth of potentially more aggressive phenotypes, can result in oligoprogression despite overall disease control. Finally, advances in therapy have resulted in the development of immuno-oncologic agents that may result in changes that are not adequately evaluated with conventional size-based response criteria and may even be misinterpreted as progression. This article reviews the common challenges a radiologist may encounter in the evaluation of patients with locally advanced and metastatic RCC. ^©RSNA, 2019.

Whole Body MRI and oncology: recent major advances

MRI is a very attractive approach for tumour detection and oncological staging with its absence of ionizing radiation, high soft tissue contrast and spatial resolution. Less than 10 years ago the use of Whole Body MRI (WB-MRI) protocols was uncommon due to many limitations, such as the forbidding acquisition times and limited availability. This decade has marked substantial progress in WB-MRI protocols. This very promising technique is rapidly arising from the research world and is becoming a commonly used examination for tumour detection due to recent technological developments and validation of WB-MRI by multiple studies and consensus papers. As a result, WB-MRI is progressively proposed by radiologists as an efficient examination for an expanding range of indications. As the spectrum of its uses becomes wider, radiologists will soon be confronted with the challenges of this technique and be urged to be trained in order to accurately read and report these examinations. The aim of this review is to summarize the validated indications of WB-MRI and present an overview of its most recent advances. This paper will briefly discuss how this examination is performed and which are the recommended sequences along with the future perspectives in the field.

Whole Body MRI and oncology: recent major advances

MRI is a very attractive approach for tumour detection and oncological staging with its absence of ionizing radiation, high soft tissue contrast and spatial resolution. Less than 10 years ago the use of Whole Body MRI (WB-MRI) protocols was uncommon due to many limitations, such as the forbidding acquisition times and limited availability. This decade has marked substantial progress in WB-MRI protocols. This very promising technique is rapidly arising from the research world and is becoming a commonly used examination for tumour detection due to recent technological developments and validation of WB-MRI by multiple studies and consensus papers. As a result, WB-MRI is progressively proposed by radiologists as an efficient examination for an expanding range of indications. As the spectrum of its uses becomes wider, radiologists will soon be confronted with the challenges of this technique and be urged to be trained in order to accurately read and report these examinations. The aim of this review is to summarize the validated indications of WB-MRI and present an overview of its most recent advances. This paper will briefly discuss how this examination is performed and which are the recommended sequences along with the future perspectives in the field.

Comparison of four MRI protocols for detection of extrahepatic colorectal cancer metastases

PURPOSE

To compare three magnetic resonance imaging (MRI) protocols containing diffusion-weighted imaging with background suppression (DWIBS) and one traditional protocol for detecting extrahepatic colorectal cancer metastases.

MATERIALS AND METHODS

Thirty patients with extrahepatic colorectal cancer metastases were scanned in three stations from the skull base to the upper thighs using a 1.5T MRI system with six different MRI sequences; transverse and coronal T₂ -weighted (T₂ W) turbo spin-echo (TSE), coronal short tau inversion recovery (STIR), 3D T₁ W TSE, DWIBS, and a contrast-enhanced T₁ W 3D gradient echo (GRE) sequence. The six sequences were used to build four hypothetical MRI interpretive sets which were read by two readers in consensus, blinded to prior imaging. Lesions were categorized into 13 anatomic regions. Fluorodeoxyglucose / positron emission tomography / computed tomography (FDG-PET/CT) read with full access to prior imaging and clinical records was used as the reference standard. Sensitivity, specificity, and false discovery rate (FDR) were calculated as appropriate and receiver operating characteristic (ROC) curves were constructed.

RESULTS

In all, 177 malignant lesions were detected by FDG-PET/CT and distributed in 92 out of 390 scanned anatomic regions. The sensitivity was statistically higher in two out of three sets incorporating DWIBS on a per-lesion basis (66.7%, 63.3%, and 66.7% vs. 57.6%) (P = 0.01, P = 0.11, and P = 0.01, respectively) and in all sets incorporating DWIBS on a per-region basis (75.0%, 75.0%, and 77.2 vs. 66.3%) (P = 0.04, P = 0.04, and P = 0.01, respectively). There was no difference in specificity, FDR, or AUC_ROC . There was no difference between sets containing DWIBS irrespective of the use of a contrast-enhanced sequence.

CONCLUSION

MRI sets containing DWIBS had superior sensitivity. This sensitivity was retained when omitting a contrast-enhanced sequence.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017;46:1619-1630.

Pre-operative staging of rectal cancer: a review of imaging techniques

INTRODUCTION

The treatment of rectal cancer has diversified in recent years, presenting the clinician and patient with increasingly challenging management decisions. At the heart of this decision-making process are two competing interests; more radical but more morbid treatments which optimize oncological outcome, and less radical treatments which preserve organs and function but may pose a greater risk of disease recurrence.

AREAS COVERED

Imaging plays a vital role informing this decision-making process, both by providing prognostic details about the cancer before the start of treatment and by updating this picture as the cancer responds or fails to respond to treatment. There is a range of available imaging modalities, each with its strengths and weaknesses. Optimizing rectal cancer treatment requires a clear understanding of the important questions that imaging needs to answer and the optimum imaging strategy. Expert Commentary: This article provides an evidence-based review of the available imaging techniques and an expert commentary on the best imaging strategy.

PET/MR Imaging in Cancers of the Gastrointestinal Tract

PET/computed tomography (PET/CT) is an established hybrid imaging technique for staging and follow-up of gastrointestinal (GI) tract malignancies, especially for colorectal carcinoma. Dedicated hybrid PET/MR imaging scanners are currently available for clinical use. Although they will not replace regular use of PET/CT, they may have utility in selected cases of GI tract malignancies. The superior soft tissue contrast resolution and depiction of anatomy and the functional information obtained from diffusion-weighted imaging (DWI) provided by MR imaging in PET/MR imaging are advantages over CT of PET/CT for T staging and follow-up of rectal carcinoma and for better characterization of liver lesions. Functional information from DWI and use of liver-specific MR imaging contrast agents are an added advantage in follow-up of liver metastases after systemic and locoregional treatment. New radiotracers will improve the utility of PET/MR imaging in staging and follow-up of tumors, which may not be [18F]-2-fluoro-2-deoxy-d-glucose avid, such as hepatocellular carcinoma and neuroendocrine tumors. PET/MR imaging also has application in selected cases of cholangiocarcinoma, gallbladder cancer, and pancreatic carcinoma for initial staging and follow-up assessment.

Comparison of hybrid FDG PET/MRI compared with PET/CT in colorectal cancer staging and restaging: a pilot study

PURPOSE

We report our initial clinical experience from a pilot study to compare the diagnostic accuracy of hybrid PET/MRI with PET/CT in colorectal cancer and discuss potential PET/MRI workflow solutions for colorectal cancer.

METHODS

Patients underwent both FDG PET/CT and PET/MRI (Ingenuity TF PET/MRI, Philips Healthcare) for rectal cancer staging or colorectal cancer restaging. The PET acquisition of PET/MRI was similar to that of PET/CT whereas the MRI protocol was selected individually based on the patient's medical history. One nuclear medicine physician reviewed the PET/CT studies and one radiologist reviewed the PET/MRI studies independently. The diagnostic accuracy of each modality was determined in consensus, using available medical records as a reference.

RESULTS

Of the 12 patients enrolled, two were for initial staging and ten for restaging. The median scan delay between the two modalities was 60 min. The initial imaging was PET/CT in nine patients and PET/MRI in three patients. When PET/CT was performed first, the SUV values of the 16 FDG avid lesions were greater at PET/MRI than at PET/CT. In contrast, when PET/MRI was performed first, the SUV values of the seven FDG avid lesions were greater at PET/CT than at PET/MRI. PET/MRI provided more detailed T staging than PET/CT. On a per-patient basis, with both patient groups combined for the evaluation of N and M staging/restaging, the true positive rate was 5/7 (71%) for PET/CT and 6/7 (86%) for PET/MRI, and true negative rate was 5/5 (100%) for both modalities. On a per-lesion basis, PET/CT identified 26 of 29 (90%) tumor lesions that were correctly detected by PET/MRI. Our proposed workflow allows for comprehensive cancer staging including integrated local and whole-body assessment.

CONCLUSIONS

Our initial experience shows a high diagnostic accuracy of PET/MRI in T staging of rectal cancer compared with PET/CT. In addition, PET/MRI shows at least comparable accuracy in N and M staging as well as restaging to PET/CT. However, the small sample size limits the generalizability of the results. It is expected that PET/MRI would yield higher diagnostic accuracy than PET/CT considering the high soft tissue contrast provided by MRI compared with CT, but larger studies are necessary to fully assess the benefit of PET/MRI in colorectal cancer.

Evidence-based medicine and clinical fluorodeoxyglucose PET/MRI in oncology

Positron Emission Tomography/Magnetic Resonance Imaging (PET/MRI) is a hybrid of two technologies each with its own evidence for clinical effectiveness. This article amalgamates evidence for clinical effectiveness of fluorodeoxyglucose (FDG) PET/CT and MRI as separate modalities with current evidence for hybrid PET/MRI and considers whether such an approach might provide a stronger case for the clinical use of PET/MRI at an earlier stage.

Because links between diagnostic accuracy and health outcomes have already been established for FDG-PET/CT in the investigation of suspected residual or recurrent malignancies, evidence showing improved diagnostic performance and therapeutic impact from the use of PET/MRI as an alternative would imply clinical effectiveness of this modality for this application. A meta-analysis of studies comparing FDG-PET/CT to MRI in patients with suspected residual disease or recurrence of tumours indicates complementary roles for these modalities. PET demonstrates greater sensitivity for recurrence within lymph nodes whereas MRI is more effective that PET/CT in the detection of skeletal and hepatic recurrence. A review of studies assessing therapeutic impact of PET/MRI suggests a greater likelihood for change in clinical management when PET/MRI is used for assessment of suspected residual or recurrent disease rather than tumour staging.

Supplementing the evidence-base for FDG-PET/MRI with studies that compare the components of this hybrid technology deployed separately indicates that FDG-PET/MRI is likely to be clinical effective for the investigation of patients with a range of suspected residual or recurrent cancers. This indication should therefore be prioritised for further health technology assessment.

BRAF and RAS mutations as prognostic factors in metastatic colorectal cancer patients undergoing liver resection

Background:

Despite major advances in the management of metastatic colorectal cancer (mCRC) with liver-only involvement, relapse rates are high and reliable prognostic markers are needed.

Methods:

To assess the prognostic impact of BRAF and RAS mutations in a large series of liver-resected patients, medical records of 3024 mCRC patients were reviewed. Eligible cases undergoing potentially curative liver resection were selected. BRAF and RAS mutational status was tested on primary and/or metastases by means of pyrosequencing and mass spectrometry genotyping assay. Primary endpoint was relapse-free survival (RFS).

Results:

In the final study population (N=309) BRAF mutant, RAS mutant and all wild-type (wt) patients were 12(4%), 160(52%) and 137(44%), respectively. Median RFS was 5.7, 11.0 and 14.4 months respectively and differed significantly (Log-rank, P=0.043). At multivariate analyses, BRAF mutant had a higher risk of relapse in comparison to all wt (multivariate hazard ratio (HR)=2.31; 95% CI, 1.09–4.87; P=0.029) and to RAS mutant (multivariate HR=2.06; 95% CI, 1.02–4.14; P=0.044). Similar results were obtained in terms of overall survival. Compared with all wt patients, RAS mutant showed a higher risk of death (HR=1.47; 95% CI, 1.05–2.07; P=0.025), but such effect was lost at multivariate analyses.

Conclusions:

BRAF mutation is associated with an extremely poor median RFS after liver resection and with higher probability of relapse and death. Knowledge of BRAF mutational status may optimise clinical decision making in mCRC patients potentially candidate to hepatic surgery. RAS status as useful marker in this setting might require further studies.

Association between carcinoembryonic antigen levels and the applied value of 18F-fluorodeoxyglucose positron emission tomography/computed tomography in post-operative recurrent and metastatic colorectal cancer

Positron emission tomography (PET) using ¹⁸F-fluorodeoxyglucose has been widely used for analyzing cellular metabolism. The present study aimed to evaluate the association between the diagnostic value of PET/computed tomography (CT) in patients with post-operative recurrent and metastatic colorectal cancer (CRC), and the different levels of carcinoembryonic antigen (CEA). A total of 105 suspected recurrent and metastatic CRC patients (67 males and 38 females; mean age, 48.5 years) were included in this retrospective study. All the patients underwent PET/CT examination. The differences in the PET/CT diagnostic values of CEA-positive and -negative patients with recurrent CRC following surgery were retrospectively analyzed and compared. Among the 105 CRC patients, 87 exhibited recurrence and metastasis, as confirmed by histopathological diagnosis or clinical follow-up data. By contrast, the PET/CT examination results revealed that 85 cases were true positives (a false positive foci was diagnosed in one of the patients), 18 were true negatives and 2 were false negatives. Correspondingly, the sensitivity and degree of accuracy were 97.7 and 97.1%, respectively. The detection rates of PET/CT for the recurrence and metastases were 85.3% in the CEA-positive group and 75.7% in the CEA-negative group. No significant differences were observed between the two groups. Overall, CEA levels do not help improve the detection rate of PET/CT in the recurrence and metastasis of CRC. PET/CT imaging has a high sensitivity and degree of accuracy in detecting recurrence and metastasis following CRC surgery. Therefore, this method is ideal for monitoring relapsed and metastatic foci of post-operative colon cancer cases.

Diagnostic accuracy of whole-body PET/MRI and whole-body PET/CT for TNM staging in oncology

PURPOSE

In various tumours PET/CT with [(18)F]FDG is widely accepted as the diagnostic standard of care. The purpose of this study was to compare a dedicated [(18)F]FDG PET/MRI protocol with [(18)F]FDG PET/CT for TNM staging in a cohort of oncological patients.

METHODS

A dedicated [(18)F]FDG PET/MRI protocol was performed in 73 consecutive patients (mean age of 59 years, range 21 - 85 years) with different histologically confirmed solid primary malignant tumours after a routine clinical FDG PET/CT scan (60 min after injection of 295 ± 45 MBq [(18)F]FDG). TNM staging according to the 7th edition of the AJCC Cancer Staging Manual was performed by two readers in separate sessions for PET/CT and PET/MRI images. Assessment of the primary tumour and nodal and distant metastases with FDG PET/CT and FDG PET/MRI was based on qualitative and quantitative analyses. Histopathology, and radiological and clinical follow-up served as the standards of reference. A McNemar test was performed to evaluate the differences in diagnostic performance between the imaging procedures.

RESULTS

From FDG PET/CT and FDG PET/MRI T stage was correctly determined in 22 (82 %) and 20 (74 %) of 27 patients, N stage in 55 (82 %) and 56 (84 %) of 67 patients, and M stage in 32 (76 %) and 35 (83 %) of 42 patients, respectively. Sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy for lymph node metastases were 65 %, 94 %, 79 %, 89 % and 87 % for PET/CT, and 63 %, 94 %, 80 %, 87 % and 85 % for PET/MRI. The respective values for the detection of distant metastases were 50 %, 82 %, 40 %, 88 % and 76 % for PET/CT, and 50 %, 91 %, 57 %, 89 % and 83 % for PET/MRI. Differences between the two imaging modalities were not statistically significant (P > 0.05).

CONCLUSION

According to our results, FDG PET/CT and FDG PET/MRI are of equal diagnostic accuracy for TNM staging in patients with solid tumours.

Diffusion-weighted MR imaging of the rectum: clinical applications

Dramatic advances in image quality over the past few years have made diffusion-weighted magnetic resonance imaging (DW-MRI) a promising tool for rectal lesion evaluation. DW-MRI derives its image contrast from differences in the motion of water molecules between tissues. Such imaging can be performed quickly without the need for the administration of exogenous contrast medium. The technique yields qualitative and quantitative information that reflects changes at a cellular level and provides information about tumor cellularity and the integrity of cell membranes. The sensitivity to diffusion is obtained by applying two bipolar diffusion-sensitizing gradients to a standard T2-weighted spin echo sequence. The diffusion-sensitivity can be varied by adjusting the "b-factor", which represents the gradient duration, gradient amplitude and the time interval between the two gradients. The higher the b-value, the greater the signal attenuation from moving water protons. In this review, technical considerations relatively to image acquisition and to quantification methods applied to rectal DW-MRI are discussed. The current clinical applications of DW-MRI, either in the field of inflammatory or neoplastic rectal disease are reviewed. Also, limitations, mainly in terms of persistent lack of standardization or evaluation of tumoral response, and future directions of rectal DW-MRI are discussed. The potential utility of DW-MRI for the evaluation of rectal tumor response is on its way to being admitted but future well-designed and multicenter studies, as well as standardization of DW-MRI, are still required before a consensus can be reached upon how and when to use DW-MRI.

Colorectal hepatic metastasis: Evolving therapies

The approach for colorectal hepatic metastasis has advanced tremendously over the past decade. Multidrug chemotherapy regimens have been successfully introduced with improved outcomes. Concurrently, adjunct multimodal therapies have improved survival rates, and increased the number of patients eligible for curative liver resection. Herein, we described major advancements of surgical and oncologic management of such lesions, thereby discussing modern chemotherapeutic regimens, adjunct therapies and surgical aspects of liver resection.

Whole-body-MR imaging including DWIBS in the work-up of patients with head and neck squamous cell carcinoma: a feasibility study

OBJECTIVES

To assess the feasibility of whole-body magnetic resonance imaging (WB-MRI) including diffusion-weighted whole-body imaging with background-body-signal-suppression (DWIBS) for the evaluation of distant malignancies in head and neck squamous cell carcinoma (HNSCC); and to compare WB-MRI findings with (18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG-PET/CT) and chest-CT.

METHODS

Thirty-three patients with high risk for metastatic spread (26 males; range 48-79 years, mean age 63 ± 7.9 years (mean ± standard deviation) years) were prospectively included with a follow-up of six months. WB-MRI protocol included short-TI inversion recovery and T1-weighted sequences in the coronal plane and half-fourier acquisition single-shot turbo spin-echo T2 and contrast-enhanced-T1-weighted sequences in the axial plane. Axial DWIBS was reformatted in the coronal plane. Interobserver variability was assessed using weighted kappa and the proportion specific agreement (PA).

RESULTS

Two second primary tumors and one metastasis were detected on WB-MRI. WB-MRI yielded seven clinically indeterminate lesions which did not progress at follow-up. The metastasis and one second primary tumor were found when combining (18)F-FDG-PET/CT and chest-CT findings. Interobserver variability for WB-MRI was κ=0.91 with PA ranging from 0.82 to 1.00. For (18)F-FDG-PET/CT κ could not be calculated due to a constant variable in the table and PA ranged from 0.40 to 0.99.

CONCLUSIONS

Our WB-MRI protocol with DWIBS is feasible in the work-up of HNSCC patients for detection and characterization of distant pathology. WB-MRI can be complementary to (18)F-FDG-PET/CT, especially in the detection of non (18)F-FDG avid second primary tumors.

Early detection of colorectal cancer recurrence in patients undergoing surgery with curative intent: current status and challenges

Despite advances in neoadjuvant and adjuvant therapy, attention to proper surgical technique, and improved pathological staging for both the primary and metastatic lesions, almost half of all colorectal cancer patients will develop recurrent disease. More concerning, this includes ~25% of patients with theoretically curable node-negative, non-metastatic Stage I and II disease. Given the annual incidence of colorectal cancer, approximately 150,000 new patients are candidates each year for follow-up surveillance. When combined with the greater population already enrolled in a surveillance protocol, this translates to a tremendous number of patients at risk for recurrence. It is therefore imperative that strategies aim for detection of recurrence as early as possible to allow initiation of treatment that may still result in cure. Yet, controversy exists regarding the optimal surveillance strategy (high-intensity vs. traditional), ideal testing regimen, and overall effectiveness. While benefits may involve earlier detection of recurrence, psychological welfare improvement, and greater overall survival, this must be weighed against the potential disadvantages including more invasive tests, higher rates of reoperation, and increased costs. In this review, we will examine the current options available and challenges surrounding colorectal cancer surveillance and early detection of recurrence.

Radiation risks associated with serial imaging in colorectal cancer patients: Should we worry?

To provide an overview of the radiation related cancer risk associated with multiple computed tomographic scans required for follow up in colorectal cancer patients. A literature search of the PubMed and Cochrane Library databases was carried out and limited to the last 10 years from December 2012. Inclusion criteria were studies where computed tomographic scans or radiation from other medical imaging modalities were used and the risks associated with ionizing radiation reported. Thirty-six studies were included for appraisal with no randomized controlled trials. Thirty-four of the thirty-six studies showed a positive association between medical imaging radiation and increased risk of cancer. The radiation dose absorbed and cancer risk was greater in children and young adults than in older patients. Most studies included in the review used a linear, no-threshold model to calculate cancer risks and this may not be applicable at low radiation doses. Many studies are retrospective and ensuring complete follow up on thousands of patients is difficult. There was a minor increased risk of cancer from ionizing radiation in medical imaging studies. The radiation risks of low dose exposure (< 50 milli-Sieverts) are uncertain. A clinically justified scan in the context of colorectal cancer is likely to provide more benefits than harm but current guidelines for patient follow up will need to be revised to accommodate a more aggressive approach to treating metastatic disease.

Local colorectal cancer recurrence: pelvic MRI evaluation

Surveillance of colorectal cancer is currently based on dosage of tumoral markers, colonoscopy and multidetector row computed tomography. However, pelvic magnetic resonance imaging (MRI) and PET-CT are two second-line useful imaging modalities to assess colorectal cancer local recurrence (LR). The anatomical information derived from MRI combined to the functional information provided by diffusion-weighted imaging currently remain of value. Pelvic MRI is accurate not only for detection of pelvic colorectal recurrence but also for the prediction of absence of tumoral invasion in pelvic structures, and it may thus provide a preoperative road map of the recurrence to allow for appropriate surgical planning. As always, correlation of imaging and clinical findings in the multidisciplinary forum is paramount. MRI can also be used to follow-up LR treated with radiofrequency ablation. The aim of this review is to discuss clinical practice and application of MRI in the assessment or pelvic recurrence from colorectal cancer.

Comparison between whole-body MRI and Fluorine-18-Fluorodeoxyglucose PET or PET/CT in oncology: a systematic review

BACKGROUND

The aim of the article is to systematically review published data about the comparison between positron emission tomography (PET) or PET/computed tomography (PET/CT) using Fluorine-18-Fluorodeoxyglucose (FDG) and whole-body magnetic resonance imaging (WB-MRI) in patients with different tumours.

METHODS

A comprehensive literature search of studies published in PubMed/MEDLINE, Scopus and Embase databases through April 2012 and regarding the comparison between FDG-PET or PET/CT and WB-MRI in patients with various tumours was carried out.

RESULTS

Forty-four articles comprising 2287 patients were retrieved in full-text version, included and discussed in this systematic review. Several articles evaluated mixed tumours with both diagnostic methods. Concerning the specific tumour types, more evidence exists for lymphomas, bone tumours, head and neck tumours and lung tumours, whereas there is less evidence for other tumour types.

CONCLUSIONS

Overall, based on the literature findings, WB-MRI seems to be a valid alternative method compared to PET/CT in oncology. Further larger prospective studies and in particular cost-effectiveness analysis comparing these two whole-body imaging techniques are needed to better assess the role of WB-MRI compared to FDG-PET or PET/CT in specific tumour types.

Detection of resectable recurrences in colorectal cancer patients with 2-[18F]fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography

PURPOSE

To evaluate the usefulness of 2-[(18)F]fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography (FDG-PET/CT) in the early detection of resectable recurrences of colorectal cancer (CRC) and the impacts on the clinical disease management.

METHODS

FDG-PET/CT was performed on patients with elevated serum carcinoembryonic antigen (CEA) levels >5 ng/mL (Group 1) or suspicious recurrences without rise in serum CEA levels (Group 2). The results were analyzed on the basis of histological data, disease progression, and/or clinical follow-up. Recurrence was defined as evidence of recurrent lesions within 6 months of the FDG-PET/CT scan. Resectable recurrences and changes in management were calculated based on medical records.

RESULTS

In our study, 128 consecutive FDG-PET/CT analyses (n=49 in Group 1 and n=79 in Group 2) were performed on 96 recruited patients. Recurrences were proven in 63. The overall sensitivity, specificity, and accuracy of FDG-PET/CT were 98.4%, 89.2%, and 93.8%, respectively, and were 100%, 88.9%, and 95.9% in Group 1 and 96.9% and 89.4% and 92.4% in Group 2, respectively. Surgical resections were performed in 38.7% (12/31) of Group 1 patients and 53.1% (17/32) of Group 2 patients. FDG-PET/CT induced changes in planned management in 48.4% (62/128) of all patients, which included 63.3% (31/49) of Group 1 patients and 39.2% (31/79) of Group 2 patients (p=0.008). After a follow-up, 3.4% (1/29) of patients who underwent surgical resection of recurrent lesions and 34.3% (11/34) patients who did not undergo resection died at the end of study (p=0.004).

CONCLUSIONS

The surgical resection of limited recurrent disease, as determined by FDG-PET/CT, improves the survival of CRC patients. FDG-PET/CT should be performed not only in patients with elevated serum CEA levels, but also in those in whom recurrences are suspected to improve the early detection of resectable disease.

Diffusion-weighted imaging as part of hybrid PET/MRI protocols for whole-body cancer staging: does it benefit lesion detection?

PURPOSE

Positron emission tomography/magnetic resonance imaging (PET/MRI) requires efficient scan protocols for whole-body cancer staging. The aim of this study was to evaluate if the application of diffusion-weighted MR imaging (DWI) results in a diagnostic benefit for lesion detection in oncologic patients if added to a whole-body [18F]-fluorodesoxyglucose ([18F]-FDG) PET/MRI protocol.

METHODS

25 consecutive oncologic patients (16 men, 9 women; age 57 ± 12 years) prospectively underwent whole-body [18F]-FDG-PET/MRI including DWI on a hybrid PET/MRI scanner. A team of two readers assessed [18F]-FDG PET/MRI without DWI for primary tumors and metastases. In a second session, now considering DWI, readers reassessed [18F]-FDG PET/MRI accordingly. Additionally, the lesion-to-background contrast on [18F]-FDG PET and DWI was rated qualitatively (0, invisible; 1, low; 2, intermediate; 3, high). Wilcoxon's signed-rank test was performed to test for differences in the lesion-to-background contrast.

RESULTS

49 lesions were detected in 16 patients (5 primaries, 44 metastases). All 49 lesions were concordantly detected by [18F]-FDG PET/MRI alone and [18F]-FDG PET/MRI with DWI. The lesion-to-background contrast on DWI compared to [18F]-FDG PET was rated lower in 22 (44.9%) of 49 detected lesions resulting in a significantly higher lesion-to-background contrast on [18F]-FDG PET compared to DWI (P=0.001).

CONCLUSIONS

DWI as part of whole-body [18F]-FDG PET/MRI does not benefit lesion detection. Given the necessity to optimize imaging protocols with regard to patient comfort and efficacy, DWI has to be questioned as a standard tool for whole-body staging in oncologic PET/MRI.

Selection for hepatic resection of colorectal liver metastases: expert consensus statement

Hepatic resection offers a chance of a cure in selected patients with colorectal liver metastases (CLM). To achieve adequate patient selection and curative surgery, (i) precise assessment of the extent of disease, (ii) sensitive criteria for chemotherapy effect, (iii) adequate decision making in surgical indication and (iv) an optimal surgical approach for pre-treated tumours are required. For assessment of the extent of the disease, contrast-enhanced computed tomography (CT) and/or magnetic resonance imaging (MRI) with gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) is recommended depending on the local expertise and availability. Positron emission tomography (PET) and PET/CT may offer additive information in detecting extrahepatic disease. The RECIST criteria are a reasonable method to evaluate the effect of chemotherapy. However, they are imperfect in predicting a pathological response in the era of modern systemic therapy with biological agents. The assessment of radiographical morphological changes is a better surrogate of the pathological response and survival especially in the patients treated with bevacizumab. Resectability of CLM is dependent on both anatomic and oncological factors. To decrease the surgical risk, a sufficient volume of liver remnant with adequate blood perfusion and biliary drainage is required according to the degree of histopathological injury of the underlying liver. Portal vein embolization is sometimes required to decrease the surgical risk in a patient with small future liver remnant volume. As a complete radiological response does not signify a complete pathological response, liver resection should include all the site of a tumour detected prior to systemic treatment.

[Importance of PET/CT for imaging of colorectal cancer]

CLINICAL/METHODICAL ISSUE

Fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) has emerged as a very useful imaging modality in the management of colorectal carcinoma. Data from the literature regarding the role of PET/CT in the initial diagnosis, staging, radiotherapy planning, response monitoring and surveillance of colorectal carcinoma is presented. Future directions and economic aspects are discussed.

STANDARD RADIOLOGICAL METHODS

Computed tomography (CT), magnetic resonance imaging (MRI) and FDG-PET for colorectal cancer and endorectal ultrasound for rectal cancer.

METHODICAL INNOVATIONS

Combined FDG-PET/CT.

PERFORMANCE

While other imaging modalities allow superior visualization of the extent and invasion depth of the primary tumor, PET/CT is most sensitive for the detection of distant metastases of colorectal cancer.

ACHIEVEMENTS

We recommend a targeted use of PET/CT in cases of unclear M staging, prior to metastasectomy and in suspected cases of residual or recurrent colorectal carcinoma with equivocal conventional imaging. The role of PET/CT in radiotherapy planning and response monitoring needs to be determined. Currently there is no evidence to support the routine use of PET/CT for colorectal screening, staging or surveillance.

PRACTICAL RECOMMENDATIONS

To optimally exploit the synergy between morphologic and functional information, FDG-PET should generally be performed as an integrated FDG-PET/CT with a contrast-enhanced CT component in colorectal carcinoma.

[Importance of whole body MRI for staging of colorectal cancer]

CLINICAL/METHODICAL ISSUE

Staging and follow-up of colorectal cancer are usually performed with multimodal imaging strategies. These can be time-intensive and potentially lead to examiner-dependent bias. Alternatively, whole body magnetic resonance imaging (WB-MRI) provides oncologic imaging with a systemic approach.

STANDARD RADIOLOGICAL METHODS

Ultrasound, multislice computed tomography (MSCT), dedicated MRI and positron emission tomography/CT (PET/CT).

METHODICAL INNOVATIONS

High-resolution WB-MRI with focused examination of various organs, such as the pelvis and abdomen, lungs, brain and skeletal system, using different sequence and contrast techniques.

PERFORMANCE

Detection of colorectal tumor recurrence with WB-MRI provides 83% accuracy (lymph node metastases 80%, organ metastases 86%).

ACHIEVEMENTS

Potential cost reduction through decreased examination time and personnel costs.

PRACTICAL RECOMMENDATIONS

Whole body MRI is a radiation-free alternative to standard sequential algorithms of staging and follow-up of colorectal cancer.

Magnetic resonance imaging as an early indicator of clinical outcome in patients with metastatic colorectal carcinoma treated with cetuximab or panitumumab

We show that detection, by week-2 magnetic resonance imaging, of tumor shrinkage >10% in response to therapy with cetuximab or panitumumab for metastatic colorectal carcinoma represents an early indicator of clinical outcome because it is predictive of the prolongation of progression-free survival and overall survival.

PURPOSE

The early identification of patients with metastatic colorectal carcinoma who are likely to benefit from treatment with panitumumab or cetuximab remains of paramount importance. We evaluated whether the early tumor shrinkage assessed by magnetic resonance imaging (MRI) is predictive of long-term outcome to these epidermal growth factor receptor-targeted therapies.

PATIENTS AND METHODS

Thirty-nine patients with chemorefractory metastatic colorectal carcinoma were treated with cetuximab or panitumumab. The patients were evaluated by unenhanced MRI at baseline, week 2, and week 8 after the beginning of the treatment and by contrast-enhanced computed tomography within 3 months. Early response was defined as a tumor shrinkage ≥ 10% at week-2 MRI, whereas response by contrast-enhanced computed tomography was defined according to standard Response Evaluation Criteria in Solid Tumors 1.1.

RESULTS

At week-2 MRI, 15 (38.5%) of 39 patients had an early response. Eleven (73.3%) of these 15 early responders then presented a partial response by contrast-enhanced computed tomography, whereas none of the 24 early nonresponders obtained a partial response (P < .0005, Fisher exact test). Median progression-free survival (PFS) was 29.7 and 8 weeks in patients with or without early response, respectively (hazard ratio [HR] 0.156 [95% CI, 0.069-0.355]; P < .0001)]. The median overall survival (OS) was 80 weeks in patients with early response and 23.3 weeks in those without early response, respectively (HR 0.154 [95% CI, 0.057-0.420]; P < .00005]).

CONCLUSIONS

Early detection of tumor response by week-2 MRI without contrast medium is associated with a prediction of clinical outcome in patients with metastatic colorectal carcinoma treated with cetuximab or panitumumab.

The utility of FDG-PET/CT as an effective tool for detecting recurrent colorectal cancer regardless of serum CEA levels

PURPOSE

Tumor recurrence of colorectal cancers (CRC) is generally followed up by analyses of the serum carcinoembryonic antigen (CEA) levels. However, recent evidence suggests that tumor recurrence can also be visualized by 18F-fluoro-deoxyglucose emission tomography/computed tomography (FDG-PET/CT) in patients with normal CEA levels. We retrospectively evaluated the diagnostic performance of FDG-PET/CT in patients with suspected recurrence of CRC by comparing PET/CT performance in patients with normal CEA levels with PET/CT performance in patients with elevated CEA levels.

METHODS

A total of 235 patients with CRC who had been treated with surgery and/or chemotherapy/radiotherapy underwent PET/CT for the detection of tumor recurrence. The patients [96 females and 139 males; age (mean ± SD) 59.9 ± 12.6 years; range 18-85] were divided into 2 groups based on whether their CEA levels were normal (<5 ng/ml) (Group 1, n = 118) or elevated (>5 ng/ml) (Group 2, n = 117). All of the patients had suspected recurrence based on raised CEA levels, clinical symptoms, and/or tumor detection using other imaging modalities.

RESULTS

Of the 235 patients, 172 (73.1 %) had disease recurrence confirmed by a pathological examination (either biopsy or surgical exploration) or clinical follow-up studies. The FDG-PET/CT study yielded a true positive in detecting recurrence in 169 (71.9 %) patients, a true negative in 53 (22.5 %) patients, a false negative in 3 (1.2 %) patients and a false positive in 10 (4.2 %) patients. CRC recurrence was detected in 64.4 % (76/118) and 88 % (103/117) patients in Group 1 and Group 2 with FDG-PET/CT, respectively. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of the FDG-PET/CT study for establishing recurrence were 100, 84, 89.4, 100 and 93.2 %, respectively, for Group 1; by contrast, these parameters were 97.1, 84.6, 98, 78.5 and 95.7 %, respectively, for Group 2. The number of patients with hepatic and extra-hepatic metastases, such as lung and abdominal lymph node metastasis, detected with FDG-PET/CT was significantly different in Group 1 than in Group 2; however, the number of patients with local recurrence and peritoneal implants detected with FDG-PET/CT was not different between the two groups.

CONCLUSIONS

FDG-PET/CT can accurately detect tumor recurrence in patients with suspected recurrent CRC, even for patients with normal CEA levels.

The clinical value of routine whole-body magnetic resonance imaging (MRI) in palliative care

BACKGROUND

Whole-body MRI (WBMRI) has become an accessible method for detecting different types of pathologies both in the skeleton and the viscera, which may explain painful conditions, for example tumors and inflammation.

PURPOSE

To assess a possible value of using WBMRI in order to improve palliative care.

MATERIAL AND METHODS

Twenty patients (all eligible patients) admitted to the Department for Palliative Care were consecutively included in this study. They underwent a modified WBMRI, with fewer and shorter pulse sequences than in a standard WBMRI, to reduce patient stress. However, the patients' physicians were to exclude patients where little might be obtained and discomfort, distress, and pain could be induced. The treating physicians registered clinical utility directly after receiving the MRI report in a questionnaire. The registration was repeated after ended treatment.

RESULTS

Eighty percent had new findings detected, and 40% of the patients had a change in treatment due to the MRI result, mainly changes in analgesics and/or radiation therapy.

CONCLUSION

The WBMRI helped the clinicians to improve treatment and a majority of the patients benefited from this. In eight patients the treatment was changed due to the results. The clinical value (utility) was indicated to be high.

Gadoxetate disodium-enhanced magnetic resonance imaging versus contrast-enhanced 18F-fluorodeoxyglucose positron emission tomography/computed tomography for the detection of colorectal liver metastases

PURPOSE

: To compare the diagnostic accuracy of gadoxetate disodium-enhanced magnetic resonance imaging (EOB-MRI) on a 3-T system and integrated contrast-enhanced F-fluorodeoxyglucose positron emission tomography/computed tomography (CE-PET/CT) for the detection of hepatic metastases from colorectal cancers.

MATERIALS AND METHODS

: The approval from the institutional review board was obtained, and the requirement for informed consent was waived. We retrospectively evaluated 135 metastases in 68 patients (37 men, 31 women; mean age: 68 years; age range: 37-82 years) who underwent both EOB-MRI and CE-PET/CT. A total of 103 metastases were confirmed during surgery and 32 were confirmed by imaging findings during follow-up. The images were independently reviewed by 2 observers. The diagnostic accuracies of EOB-MRI and CE-PET/CT were determined by calculating the areas under each reader-specific receiver operating characteristic curve (Az). Patient-based lesion sensitivity and specificity were compared using the McNemar test.

RESULTS

: The mean area under the Az on EOB-MRI versus CE-PET/CT was 0.94 versus 0.81 for all lesions (P < 0.001), 0.92 versus 0.60 for lesions ≤1 cm in size (P < 0.001), and 0.88 versus 0.96 for lesions >1 cm (P = 0.098), respectively. The sensitivity, specificity, positive predictive values, and negative predictive value on a patient basis were 100%, 71%, 97%, and 100% for EOB-MRI and 93%, 71%, 97%, and 57% for CE-PET/CT, respectively.

CONCLUSIONS

: EOB-MRI using a 3-T system is more accurate than CE-PET/CT, especially for the detection of small (≤1.0 cm) lesions. Patient-based analysis revealed that EOB-MRI has a higher sensitivity and negative predictive value than CE-PET/CT.

An outlook on future design of hybrid PET/MRI systems

Early diagnosis and therapy increasingly operate at the cellular, molecular, or even at the genetic level. As diagnostic techniques transition from the systems to the molecular level, the role of multimodality molecular imaging becomes increasingly important. Positron emission tomography (PET) and magnetic resonance imaging (MRI) are powerful techniques for in vivo molecular imaging. The inability of PET to provide anatomical information is a major limitation of standalone PET systems. Combining PET and CT proved to be clinically relevant and successfully reduced this limitation by providing the anatomical information required for localization of metabolic abnormalities. However, this technology still lacks the excellent soft-tissue contrast provided by MRI. Standalone MRI systems reveal structure and function but cannot provide insight into the physiology and/or the pathology at the molecular level. The combination of PET and MRI, enabling truly simultaneous acquisition, bridges the gap between molecular and systems diagnosis. MRI and PET offer richly complementary functionality and sensitivity; fusion into a combined system offering simultaneous acquisition will capitalize the strengths of each, providing a hybrid technology that is greatly superior to the sum of its parts. A combined PET/MRI system provides both the anatomical and structural description of MRI simultaneously with the quantitative capabilities of PET. In addition, such a system would allow exploiting the power of MR spectroscopy (MRS) to measure the regional biochemical content and to assess the metabolic status or the presence of neoplasia and other diseases in specific tissue areas. This paper briefly summarizes state-of-the-art developments and latest advances in dedicated hybrid PET/MRI instrumentation. Future prospects and potential clinical applications of this technology will also be discussed.

False-Positive Mediastinal Lymphadenopathy on 18F-Fluorodeoxyglucose Positron Emission Tomography and Computed Tomography after Rectal Cancer Resection: A Case Report of Thoracoscopic Surgery in the Prone Position

¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography and computed tomography (integrated FDG PET/CT) has been used to diagnose recurrence and differentiate postoperative changes from lymph node metastasis in colorectal cancer, although its accuracy is questionable. We report a prone thoracoscopic surgery for a rectal cancer patient in which false-positive mediastinal lymph nodes were found on FDG-PET/CT. A 60-year-old man underwent a laparoscopic high anterior resection and D3 lymph node dissection for rectal cancer. The histopathological diagnosis was moderately differentiated adenocarcinoma of the rectum, stage IIIB (pT3N1M0), necessitating oral fluoropyrimidine agent S-1. After the primary surgery, a solitary mediastinal lymph node measuring 30 mm in diameter was detected, and abnormal accumulation was confirmed by FDG-PET/CT (SUV_max, 11.7). Thoracoscopic resection was performed in the prone position, but histopathological results showed no metastasis. He was subsequently diagnosed with reactive lymphadenitis. The patient was discharged on postoperative day 4 in good condition and is alive without recurrence 12 months after surgery. PET/CT is useful for the detection of colorectal cancer recurrence; however, it does have a high false-positive rate for mediastinal lymph nodes. There is a limit to its diagnostic accuracy, and one must determine the indication for surgical treatment carefully. Surgery in the prone position is a useful and minimally invasive approach to the mediastinum and allows aggressive resection to be performed.

Utility of low dose (18)F-FDG PET-CT in patients with suspected colorectal carcinoma recurrence in conventional diagnostic methods

OBJECTIVE

To evaluate the efficacy of (18)F-FDG PET-CT in the diagnosis of recurrence of colorectal cancer (CRC) in patients with elevated values of carcinoembryonic antigen (CEA) and/or signs of recurrence in the multidetector CT (MDCT), and to demonstrate that good results can be obtained applying the ALARA principles.

MATERIAL AND METHODS

A retrospective study of 54 patients with suspected CRC, who underwent an (18)F-FDG PET-CT, administering a mean dose of 222 MBq (6 mCi) of (18)F-FDG, from 07/2007 to 01/2011 was carried out. Seven patients were excluded, thus studying 47 (27 males, 20 females, mean age 63 years). Recurrence was confirmed by histopathology study in 14 cases and by clinical evolution in 33. The patients were divided into 4 groups. A: patients with elevation of CEA and suspected recurrence in the MDCT. B: elevation of CEA, without suspicious lesions in the MDCT. C: normal levels of CEA and positive MDCT. D: normal levels of CEA and uncertain MDCT.

RESULTS

We found sensitivity, specificity, PPV, NPV and overall accuracy of 91%, 69%, 89%, 75% and 85% respectively. For group A, we found 100% sensitivity, in group B, 75% sensitivity with 100% specificity%, for C, sensitivity was 89% with 71% specificity. Finally, in group D, sensitivity was 100% and specificity 60%, respectively.

CONCLUSION

Applying a low dose, the (18)F-FDG PET-CT has high diagnostic performance in patients with suspicion of CRC, approaching in a higher grade the ALARA criteria.

What is the most accurate whole-body imaging modality for assessment of local and distant recurrent disease in colorectal cancer? A meta-analysis : imaging for recurrent colorectal cancer

PURPOSE

The objective of this study was to compare the diagnostic performance of positron emission tomography (PET), PET/CT, CT and MRI as whole-body imaging modalities for the detection of local and/or distant recurrent disease in colorectal cancer (CRC) patients who have a (high) suspicion of recurrent disease, based on clinical findings or rise in carcinoembryonic antigen (CEA).

METHODS

A meta-analysis was undertaken. PubMed and Embase were searched for studies on the accuracy of whole-body imaging for patients with suspected local and/or distant recurrence of their CRC. Additionally, studies had to have included at least 20 patients with CRC and 2 × 2 contingency tables had to be provided or derivable. Articles evaluating only local recurrence or liver metastasis were excluded. Summary receiver-operating characteristic (ROC) curves were constructed from the data on sensitivity and specificity of individual studies and pooled estimates of diagnostic odds ratios (DORs) and areas under the ROC curve (AUCs) were calculated. To test for heterogeneity the Cochran Q test was used.

RESULTS

Fourteen observational studies were included which evaluated PET, PET/CT, CT and/or MRI. Study results were available in 12 studies for PET, in 5 studies for CT, in 5 studies for PET/CT and in 1 study for MRI. AUCs for PET, PET/CT and CT were 0.94 (0.90-0.97), 0.94 (0.87-0.98) and 0.83 (0.72-0.90), respectively. In patient based analyses PET/CT had a higher diagnostic performance than PET with an AUC of 0.95 (0.89-0.97) for PET/CT vs 0.92 (0.86-0.96) for PET.

CONCLUSION

Both whole-body PET and PET/CT are very accurate for the detection of local and/or distant recurrent disease in CRC patients with a (high) suspicion of recurrent disease. CT has the lowest diagnostic performance. This difference is probably mainly due to the lower accuracy of CT for detection of extrahepatic metastases (including local recurrence). For clinical practice PET/CT might be the modality of choice when evaluating patients with a (high) suspicion of recurrent disease, because of its best performance in patient based analyses and confident prediction of disease status.

FDG-PET-CT and whole-body MRI for triage in patients planned for radioembolisation therapy

PURPOSE

The purpose was to evaluate the potential of FDG-PET-CT and whole-body MRI (WB-MRI) as diagnostic triage methods for patients planned for radioembolisation of metastatic liver disease.

MATERIALS AND METHODS

135 patients with multifocal liver metastases were evaluated for potential palliative therapy with radioembolisation using 90-Yttrium microspheres. All patients were examined consecutively with FDG-PET-CT and WB-MRI for exclusion of relevant extra-hepatic tumor manifestations. All patients underwent 99mTc-albumine angiography followed by scintigraphy to exclude significant hepato-pulmonary shunting.

RESULTS

Out of the 135 patients included into the pre-therapeutic diagnostic algorithm, 56% were eligible and received radioembolisation, while 44% could not be treated. In 91% the exclusion criteria was diagnosis of significant extra-hepatic metastatic disease. In 85% exclusion diagnosis was made concordantly by both FDG-PET-CT and WB-MRI, in 9% diagnosis was provided by PET-CT, in 6% by WB-MRI alone. Patient-based sensitivity for detection of extra-hepatic disease was 94% for PET-CT and 91% for WB-MRI. False-positive diagnosis of extrahepatic disease leading to exclusion for radioembolisation therapy was made in 2% of patients, in one patient by PET-CT and in one patient by WB-MRI alone. Overall, specificity for inclusion of radioembolisation therapy by combining both modalities was 99%. In 9% of patients angiographic diagnosis made radioembolisation impossible, in 7% solely the angiographic findings were decisive.

CONCLUSION

Both FDG-PET-CT and WB-MRI are efficient diagnostic triage methods for patients planned for radioembolisation of liver metastases. Overall, FDG-PET-CT shows a trend to higher diagnostic accuracy compared to WB-MRI and may be used as imaging method of choice as a standalone examination. In combination, both modalities exhibited high sensitivity for the diagnosis of extra-hepatic tumor manifestations and result in high specificity.

Molecular imaging in oncology: the acceptance of PET/CT and the emergence of MR/PET imaging

In the last decade, PET-only systems have been phased out and replaced with PET-CT systems. This merger of a functional and anatomical imaging modality turned out to be extremely useful in clinical practice. Currently, PET-CT is a major diagnostic tool in oncology. At the dawn of the merger of MRI and PET, another breakthrough in clinical imaging is expected. The combination of these imaging modalities is challenging, but has particular features such as imaging biological processes at the same time in specific body locations.

Diagnostic accuracy of whole-body MRI/DWI image fusion for detection of malignant tumours: a comparison with PET/CT

OBJECTIVE

To prospectively evaluate the diagnostic accuracy of whole-body T2-weighted (wbT2), whole-body diffusion-weighted imaging (wbDWI) and wbT2/wbDWI image fusion for malignant tumour detection compared with PET/CT.

METHODS

Sixty-eight patients (44 men; 60 ± 14 years) underwent PET/CT for staging of malignancy and were consecutively examined by 1.5-Tesla MRI including wbT2 and wbDWI. Two radiologists independently assessed wbDWI, wbT2, wbT2 + wbDWI (side-by-side) and wbT2 + wbDWI + wbT2/wbDWI image fusion for the presence of malignancy. PET/CT served as a reference standard.

RESULTS

PET/CT revealed 374 malignant lesions in 48/64 (75%) patients. Detection rates and positive predictive value (PPV) of wbT2 and wbDWI alone were 64% and 84%, and 57% and 93%, respectively. Detection rates and PPV of wbT2 and wbDWI for side-by-side analysis without and with fused images were 72% and 89%, and 74% and 91%, respectively. The detection rate was significantly higher with side-by-side analysis and fused image analysis compared with wbT2 and wbDWI alone (p = .0159; p < .0001). There was no significant difference between fused image interpretation and side-by-side analysis.

CONCLUSIONS

WbDWI allows detection of malignant lesions with a similar detection rate to wbT2. Side-by-side analysis of wbT2 and wbDWI significantly improves the overall detection rate and fused image data provides no added value.