Assessment of liver metastases from colorectal adenocarcinoma following chemotherapy: SPIO-MRI versus FDG-PET/CT

PET/CT in assessment of colorectal liver metastases: a comprehensive review with emphasis on 18F-FDG

Approximately 25% of those who are diagnosed with colorectal cancer will develop colorectal liver metastases (CRLM) as their illness advances. Despite major improvements in both diagnostic and treatment methods, the prognosis for patients with CRLM is still poor, with low survival rates. Accurate employment of imaging methods is critical in identifying the most effective treatment approach for CRLM. Different imaging modalities are used to evaluate CRLM, including positron emission tomography (PET)/computed tomography (CT). Among the PET radiotracers, fluoro-18-deoxyglucose (18F-FDG), a glucose analog, is commonly used as the primary radiotracer in assessment of CRLM. As the importance of 18F-FDG-PET/CT continues to grow in assessment of CRLM, developing a comprehensive understanding of this subject becomes imperative for healthcare professionals from diverse disciplines. The primary aim of this article is to offer a simplified and comprehensive explanation of PET/CT in the evaluation of CRLM, with a deliberate effort to minimize the use of technical nuclear medicine terminology. This approach intends to provide various healthcare professionals and researchers with a thorough understanding of the subject matter.

The Value of 18F-FDG-PET-CT Imaging in Treatment Evaluation of Colorectal Liver Metastases: A Systematic Review

(1) Background: Up to 50% of patients with colorectal cancer either have synchronous colorectal liver metastases (CRLM) or develop CRLM over the course of their disease. Surgery and thermal ablation are the most common local treatment options of choice. Despite development and improvement in local treatment options, (local) recurrence remains a significant clinical problem. Many different imaging modalities can be used in the follow-up after treatment of CRLM, lacking evidence-based international consensus on the modality of choice. In this systematic review, we evaluated ¹⁸F-FDG-PET-CT performance after surgical resection, thermal ablation, radioembolization, and neoadjuvant and palliative chemotherapy based on current published literature. (2) Methods: A systematic literature search was performed on the PubMed database. (3) Results: A total of 31 original articles were included in the analysis. Only one suitable study was found describing the role of ¹⁸F-FDG-PET-CT after surgery, which makes it hard to draw a firm conclusion. ¹⁸F-FDG-PET-CT showed to be of additional value in the follow-up after thermal ablation, palliative chemotherapy, and radioembolization. ¹⁸F-FDG-PET-CT was found to be a poor to moderate predictor of pathologic response after neoadjuvant chemotherapy. (4) Conclusions: ¹⁸F-FDG-PET-CT is superior to conventional morphological imaging modalities in the early detection of residual disease after thermal ablation and in the treatment evaluation and prediction of prognosis during palliative chemotherapy and after radioembolization, and ¹⁸F-FDG-PET-CT could be considered in selected cases after neoadjuvant chemotherapy and surgical resection.

Nanomaterials for In Vivo Imaging

In vivo imaging, which enables us to peer deeply within living subjects, is producing tremendous opportunities both for clinical diagnostics and as a research tool. Contrast material is often required to clearly visualize the functional architecture of physiological structures. Recent advances in nanomaterials are becoming pivotal to generate the high-resolution, high-contrast images needed for accurate, precision diagnostics. Nanomaterials are playing major roles in imaging by delivering large imaging payloads, yielding improved sensitivity, multiplexing capacity, and modularity of design. Indeed, for several imaging modalities, nanomaterials are now not simply ancillary contrast entities, but are instead the original and sole source of image signal that make possible the modality's existence. We address the physicochemical makeup/design of nanomaterials through the lens of the physical properties that produce contrast signal for the cognate imaging modality-we stratify nanomaterials on the basis of their (i) magnetic, (ii) optical, (iii) acoustic, and/or (iv) nuclear properties. We evaluate them for their ability to provide relevant information under preclinical and clinical circumstances, their in vivo safety profiles (which are being incorporated into their chemical design), their modularity in being fused to create multimodal nanomaterials (spanning multiple different physical imaging modalities and therapeutic/theranostic capabilities), their key properties, and critically their likelihood to be clinically translated.

Diagnostic accuracy and impact on management of (18)F-FDG PET and PET/CT in colorectal liver metastasis: a meta-analysis and systematic review

PURPOSE

The first aim of the review (aim 1) was to obtain the diagnostic performance values of (18)F-FDG PET for the detection and staging of liver metastases in patients with colorectal cancer (CRC), the second aim (aim 2) was to compare PET and conventional imaging modalities, and the third aim (aim 3) was to evaluate the impact of PET on patient management. The incidence of extrahepatic disease (EHD) detected by PET is also reviewed.

METHODS

A comprehensive search was performed on PubMed/MEDLINE for studies evaluating PET and PET/CT in CRC patients with liver metastases up to June 2014. For inclusion PET had to have been performed prior to surgery, there had to be at least 18 patients in the study, and the reported data had to allow calculation of 2 × 2 contingency tables (for aim 1). A total of 18 studies were eligible for at least one of the three intended subanalyses including a total of 1,059 patients. Pooled sensitivity, specificity and accuracy and the corresponding 95 % confidence intervals were derived from the contingency tables on a patient basis (patient-based analysis, PBA) and a lesion basis (lesion-based analysis, LBA) for eight studies.

RESULTS

Pooled sensitivity and specificity of PET on PBA were both 93 %. Corresponding values for LBA were 60 % and 79 %, respectively. Areas under the summary ROC were 0.97 for PBA and 0.67 for LBA. Regarding aim 2, PET had a slightly lower sensitivity than MRI and CT on PBA (93 %, 100 % and 98 %, respectively) and LBA (66 %, 89 % and 79 %, respectively) but appeared to be more specific than MRI and CT (86 %, 81 % and 67 %, respectively). PET findings resulted in changes in the management of a mean of 24 % of patients. The mean incidence of PET-based EHD was 32 %.

CONCLUSION

This meta-analysis suggests that FDG PET/CT is highly accurate for the detection of liver metastases on a patient basis but less accurate on a lesion basis. Compared to MRI, PET is less sensitive but more specific and affects the management of about one-quarter of patients.

Diagnostic accuracy of MR imaging to identify and characterize focal liver lesions: comparison between gadolinium and superparamagnetic iron oxide contrast media

To compare the diagnostic value of gadolinium (Gd) and ultrasmall superparamagnetic iron oxide (SPIO) contrast media for characterization of focal liver lesions (FLL), we retrospectively evaluated the results of magnetic resonance (MR) imaging in 68 patients (40 M, 28 F, age from 22 to 81 yrs) of which 36 with diagnosis of colo-rectal cancer, 26 with hepatic cirrhosis and 6 with incidental imaging detection of FLL. MR (Gyroscan Intera 1.5 T, Philips Medical Systems) study was performed using T1 and T2 fast-field-echo (FFE) and T2 turbo-spin-echo (TSE) sequences in axial and coronal views. Dynamic multi-phases gadolinium Gd-enhanced T1-FFE-Bh images were obtained in arterial, portal and equilibrium phases, followed by SPIO-enhanced T2-FFE scans. A qualitative analysis of pre- and post-contrast MR images to classify FLL as benign or malignant was performed using a 3-point scoring system: 0= benign; 1= suspicious for malignancy; 2= malignant. A total of 118 lesions were evaluated. In particular, histology (n=18), cytology (n=14) or clinical-imaging follow-up data (n=86) demonstrated 4 adenomas, 29 cysts, 3 focal steatosis, 25 hemangiomas, 1 focal vascular abnormality, 5 fibrotic lesions as well as 13 regenerative nodules, 6 dysplastic, 14 hepatocellular carcinomas (HCC), 17 metastasis and 1 cholangiocarcinoma. For MR imaging, diagnostic accuracy, sensitivity, specificity, positive (PPV) and negative (NPV) predictive values of Gd vs. SPIO images were respectively 83% vs. 92%, 79% vs. 74%, 85% vs. 99% (P=0.002), 68% vs. 96% (P=0.005) and 91% vs. 90%, respectively. The results suggest that SPIO-MR provides a diagnostic incremental value, as specificity and PPV, particularly to characterize FLL compared to Gd-MR; thus, we strongly recommend the use of SPIO when liver lesion characterization is requested and Gd images are uncertain.

Multifunctional Chitosan Magnetic-Graphene (CMG) Nanoparticles: a Theranostic Platform for Tumor-targeted Co-delivery of Drugs, Genes and MRI Contrast Agents

Combing chemotherapy with gene therapy has been one of the most promising strategies for the treatment of cancer. The noninvasive MRI with superparamagnetic iron oxide (SPIO) as contrast agent is one of the most effecitve techniques for evaluating the antitumor therapy. However, to construct a single system that can deliver efficiently gene, drug and SPIO to the cancer site remains a challenge. Herein, we report a chitosan functionalized magnetic graphene nanoparticle (CMG) platform for simultaneous gene/drug and SPIO delivery to tumor. The phantom and ex vivo MRI images suggest CMG as a strong T2 contrast-enhancing agent. The CMGs are biocompatible as evaluated by the WST assay and predominantly accumulate in tumors as shown by biodistribution studies and MRI. The anticancer drug doxorubicin (DOX) loaded CMGs (DOX-CMGs) release DOX faster at pH 5.1 than at pH 7.4, and more effective (IC50 = 2 μM) in killing A549 lung cancer cells than free DOX (IC50 = 4 μM). CMGs efficiently deliver DNA into A549 lung cancer cells and C42b prostate cancer cells. In addition, i.v. administration of GFP-plasmid encapsulated within DOX-CMGs into tumor-bearing mice has showed both GFP expression and DOX accumulation at the tumor site at 24 and 48 hrs after administration. These results indicate CMGs provide a robust and safe theranostic platform, which integrates targeted delivery of both gene medicine and chemotherapeutic drug(s), and enhanced MR imaging of tumors. The integrated chemo- and gene- therapeutic and diagnostic design of CMG nanoparticles shows promise for simultaneous targeted imaging, drug delivery and real -time monitoring of therapeutic effect for cancer.

Preoperative imaging of colorectal liver metastases after neoadjuvant chemotherapy: a meta-analysis

Background

Chemotherapy treatment induces parenchymal changes that potentially affect imaging of CRLM. The purpose of this meta-analysis was to provide values of diagnostic performance of magnetic resonance imaging (MRI), computed tomography (CT), fluorodeoxyglucose positron emission tomography (FDG-PET), and FDG-PET/CT for preoperative detection of colorectal liver metastases (CRLM) in patients treated with neoadjuvant chemotherapy.

Methods

A comprehensive search was performed for original articles published from inception to 2011 assessing diagnostic performance of MRI, CT, FDG-PET, or FDG-PET/CT for preoperative evaluation of CRLM following chemotherapy. Intraoperative findings and/or histology were used as reference standard. For each imaging modality we calculated pooled sensitivities for patients who received neoadjuvant chemotherapy as well as for chemonaive patients, defined as number of malignant lesions detected divided by number of malignant lesions as confirmed by the reference standard.

Results

A total of 11 papers, comprising 223 patients with 906 lesions, were included. Substantial variation in study design, patient characteristics, imaging features, and reference tests was observed. Pooled sensitivity estimates of MRI, CT, FDG-PET, and FDG-PET/CT were 85.7% (69.7–94.0%), 69.9% (65.6–73.9%), 54.5% (46.7–62.1%), and 51.7% (37.8–65.4%), respectively. In chemonaive patients, sensitivity rates were 80.5% (67.0–89.4%) for CT, 81.3% (64.1–91.4%) for FDG-PET, and 71.0% (64.3–76.9%) for FDG-PET/CT. Specificity could not be calculated because of non-reporting of “true negative lesions.”

Conclusion

In the neoadjuvant setting, MRI appears to be the most appropriate imaging modality for preoperative assessment of patients with CRLM. CT is the second-best diagnostic modality and should be used in the absence of MRI. Diagnostic accuracy of FDG-PET and PET-CT is strongly affected by chemotherapy.

Diagnostic value of contrast-enhanced ultrasound, computed tomography and magnetic resonance imaging for focal liver lesions: a meta-analysis

The diagnostic performance of contrast-enhanced ultrasound (CEUS), contrast-enhanced computed tomography (CECT) and contrast-enhanced magnetic resonance imaging (CEMRI) was determined in patients with focal liver lesions (FLLs) in a meta-analysis. Meta-Disc version 1.4 was used to describe and calculate sensitivity, specificity, summary receiver operating characteristic (SROC) curves and area under the curve (AUC). In the 25 included studies, the pooled estimate of CEUS studies for sensitivity, specificity and diagnostic odds ratio (DOR) was 87% (95% CI 85-88), 89% (95% CI 87-91) and 78.84 (95% CI 29.40-211.40), respectively. Sensitivity, specificity and DOR were 86% (95% CI 84-88), 82% (95% CI 77-86) and 26.34 (95% CI 8.32-83.39), respectively, for the CECT studies. Sensitivity, specificity and DOR were 85% (95% CI 82-88), 87% (95% CI 83-91) and 48.37 (95% CI 15.87-147.45), respectively, for the CEMRI studies. SROC analysis indicated that the diagnostic value of CEUS for FLLs is not significantly different from that of CECT and CEMRI.