Colorectal liver metastases: CT, MR imaging, and PET for diagnosis--meta-analysis

A nomogram for predicting subsequent liver metastasis in patients with metastatic breast cancer

Background

To investigate the clinical characteristics of liver metastasis from metastatic breast cancer and construct a competing risk nomogram for predicting the probability of liver metastasis.

Methods

Clinical data of patients with metastatic breast cancer from Tianjin Medical University Cancer Institute during 2008-2018 were retrospectively collected. Independent prognostic factors were assessed by the Fine-Gray competing risk model. A competing risk nomogram was constructed by integrating those independent prognostic factors and evaluated with concordance index (C-index) and calibration curves.

Results

A total of 1406 patients were retrospectively analyzed, and randomly divided into the training set (n=986) and the validation set (n=420). Multivariate analysis showed that menopausal status, HER-2 status, bone metastasis and lung metastasis were identified as independent prognostic factors in the nomogram. The C-index in the training set was 0.719 (95% CI: 0.706-0.732), and in the validation set was 0.740 (95% CI: 0.720-0.732). The calibration curves in the training set and validation set showed that the nomogram had a sufficient level of calibration. A risk stratification was further established to divide all the patients into three prognostic groups.

Conclusion

We had developed a tool that can predict subsequent liver metastasis from metastatic breast cancer, which may be useful for identifying the patients at risk of liver metastasis and guiding the individualized treatment. It had been verified that the nomogram has good discrimination and calibration, and had certain potential clinical value. This nomogram can be used to screen patients with low, intermediate and high risk of liver metastasis from metastatic breast cancer, so as to develop a more complete follow-up plan.

Diagnostic performance of contrast-enhanced CT combined with contrast-enhanced MRI for colorectal liver metastases: a case-control study

BACKGROUND

Colorectal liver metastases (CRLM) are a major determinant of prognosis in colorectal cancer (CRC) patients. Their early and accurate detection is essential for appropriate therapeutic planning and improving survival outcomes.

PURPOSE

To evaluate the diagnostic capabilities of contrast-enhanced computed tomography (CT) and contrast-enhanced magnetic resonance imaging (MRI) in detecting colorectal liver metastases.

MATERIALS AND METHODS

We employed a case-control design to compare patients with histologically confirmed liver metastases against a control group without the condition. A total of 85 patients in each group were selected and retrospectively matched based on relevant factors. All subjects underwent both contrast-enhanced CT and MRI. The diagnostic performance of these imaging modalities was assessed by analysing sensitivity, specificity, positive and negative predictive values, and radiologists' diagnostic confidence. Kappa statistics were used to evaluate inter-observer agreement. All MRI scans were performed using a 3-Tesla (3-T) MRI scanner to ensure high-quality imaging and detailed lesion characterization. And all the scans were reviewed by two radiologists.

RESULTS

The combination of contrast-enhanced CT and MRI demonstrated a statistically significant improvement in sensitivity (90.6% for MRI alone vs. 96.5% for combined modalities) and specificity (95.3% for MRI alone vs. 98.3% for combined modalities). Positive and negative predictive values were similarly enhanced. Radiologists' diagnostic confidence was higher with combined imaging, achieving a 'very high' confidence level in 78.8% of cases compared with 64.7% for MRI alone. The inter-observer agreement reached 'almost perfect' status with the combined approach.

CONCLUSION

The integration of contrast-enhanced CT with MRI significantly enhanced the diagnostic accuracy for colorectal liver metastases, representing a valuable tool for the preoperative evaluation of patients with CRC.

CLINICAL TRIAL NUMBER

Not applicable.

Photon-Counting CT Effects on Sensitivity for Liver Lesion Detection: A Reader Study Using Virtual Imaging

Background Detection of hepatic metastases at CT is a daily task in radiology departments that influences medical and surgical treatment strategies for oncology patients. Purpose To compare simulated photon-counting CT (PCCT) with energy-integrating detector (EID) CT for the detection of small liver lesions. Materials and Methods In this reader study (July to December 2023), a virtual imaging framework was used with 50 anthropomorphic phantoms and 183 generated liver lesions (one to six lesions per phantom, 0.4-1.5 cm in diameter). Virtual CT platforms simulated PCCT and EID CT scanners. Phantoms were virtually scanned using routine (6 mGy) and low-dose (1.5 mGy) conditions and reconstructed with three kernels. A subset of 300 scans (150 PCCT vs EID CT pairs) were selected. Four radiologists independently reviewed all scans to mark liver lesions, assigned confidence scores for detection, and rated scan quality. Analysis was performed on a per-lesion basis to determine sensitivity for several variables and on a per-scan basis for scan quality. The McNemar test, two-sided paired t tests, and mixed-effects logistic regression models were fitted; P < .05 was considered indicative of statistically significant difference. Results Consensus reader sensitivity in detecting lesions was 82.1% (451 of 549) for PCCT versus 77.6% (426 of 549) for EID CT (P < .001), with a mean sensitivity gain of 4.3 percentage points ± 1.3 (P < .001 to P = .02 per reader). Readers had better subjective confidence for lesions at PCCT (mean score, 61.5 ± 22 vs 56.1 ± 24 [on a 101-point scale]; P < .001). Sensitivity was lower for lesions smaller than 1 cm, with more pronounced difference between PCCT and EID CT (74.0% [271 of 366] vs 67.2% [246 of 366]; P < .001). At the lower dose level, PCCT showed higher sensitivity than EID CT (68.9% [168 of 244] vs 61.1% [149 of 244]; P < .001) for subcentimeter lesions. In a multivariable model, PCCT was independently associated with increased odds of lesion detection (odds ratio, 1.55; P < .001). Image quality was slightly higher for PCCT (mean score, 55.3 vs 50.6 [on a 101-point scale]; P < .001). Conclusion Compared with EID CT, PCCT showed better sensitivity in the detection of small liver lesions. © RSNA, 2025 Supplemental material is available for this article. See also the editorial by Menu in this issue.

Medullary Thyroid Carcinoma: Imaging

Imaging plays an important role in the early detection and staging of medullary thyroid carcinoma (MTC), as well as in follow-up to locate early recurrence. MTC is a rare, calcitonin-secreting thyroid malignancy that is often diagnosed by ultrasound and calcitonin screening as part of the routine evaluation of any thyroid nodule. If serum calcitonin is elevated, imaging studies are needed for preoperative staging to guide surgical management. This may include ultrasound of the neck and abdomen. CT or MRI studies for more distant disease are performed preoperatively when calcitonin levels are greater than 500 pg/mL. Neither FDG-PET/CT nor F-DOPA-PET/CT is routinely being used for preoperative staging, but may be helpful in individual cases of doubt. Postoperative elevated calcitonin is associated with persistence or recurrence of MTC. Imaging studies to localize tumor tissue in postoperative follow-up include ultrasound, CT, MRI, and PET scans. However, they should be used judiciously, as the impact of treatment is often limited. In addition, even patients with persistent disease may survive long enough to accumulate significant radiation doses from CT or PET scans. Imaging studies are also useful in diagnosing associated components of hereditary MTC, such as pheochromocytoma and primary hyperparathyroidism.

CEUS compared with CECT, MRI, and FDG-PET/CT for diagnosing CRC liver metastases: a diagnostic test accuracy systematic review and meta-analysis

OBJECTIVE

To determine the diagnostic accuracy of contrast-enhanced ultrasound (CEUS) compared with contrast-enhanced computed tomography (CECT), magnetic resonance imaging (MRI), and Fluorine-18-deoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) for diagnosing suspected liver metastases in patients with newly diagnosed colorectal cancer (CRC).

METHODS

The meta-analysis using the bivariate model included studies on patients with newly diagnosed CRC only and excluded patients with non-CRC liver metastases, known liver metastases, patients treated with chemotherapy and local treatments, e.g. hepatic resection or radiofrequency ablation. We used QUADAS-2 to assess the methodological quality of the studies.

RESULTS

We included 32 studies, 6 studies evaluated the accuracy of CEUS (n = 937 participants), 26 studies evaluated CECT (n = 2,582), 8 studies evaluated MRI (n = 564) and 6 studies evaluated FDG-PET/CT (n = 813). Sensitivity: FDG-PET/CT 94.4% [95% CI: 90.7-98.1%], MRI 92.9% [95% CI: 88.8-97.0%], CEUS 86.1% [95% CI: 78.0-94.3%] and CECT 84.6% [95% CI: 79.3-89.9%]. Specificity FDG-PET/CT 97.9% [95% CI: 95.9-99.9%], CEUS 96.1% [95% CI: 93.6-98.6%], MRI 94.4% [95% CI: 90.5-98.3%], and CECT 94.3% [95% CI: 91.8-96.8%].

CONCLUSION

FDG-PET/CT had significantly higher sensitivity and specificity than CECT, and significantly higher sensitivity than CEUS. MRI had a significantly higher sensitivity than CEUS, but a lower non-significant specificity. CECT had the lowest sensitivity and specificity.

PROSPERO REGISTRATION DETAILS

CRD42017055015 and CRD42017082996.

Immunological nanomaterials to combat cancer metastasis

Metastasis causes greater than 90% of cancer-associated deaths, presenting huge challenges for detection and efficient treatment of cancer due to its high heterogeneity and widespread dissemination to various organs. Therefore, it is imperative to combat cancer metastasis, which is the key to achieving complete cancer eradication. Immunotherapy as a systemic approach has shown promising potential to combat metastasis. However, current clinical immunotherapies are not effective for all patients or all types of cancer metastases owing to insufficient immune responses. In recent years, immunological nanomaterials with intrinsic immunogenicity or immunomodulatory agents with efficient loading have been shown to enhance immune responses to eliminate metastasis. In this review, we would like to summarize various types of immunological nanomaterials against metastasis. Moreover, this review will summarize a series of immunological nanomaterial-mediated immunotherapy strategies to combat metastasis, including immunogenic cell death, regulation of chemokines and cytokines, improving the immunosuppressive tumour microenvironment, activation of the STING pathway, enhancing cytotoxic natural killer cell activity, enhancing antigen presentation of dendritic cells, and enhancing chimeric antigen receptor T cell therapy. Furthermore, the synergistic anti-metastasis strategies based on the combinational use of immunotherapy and other therapeutic modalities will also be introduced. In addition, the nanomaterial-mediated imaging techniques (e.g., optical imaging, magnetic resonance imaging, computed tomography, photoacoustic imaging, surface-enhanced Raman scattering, radionuclide imaging, etc.) for detecting metastasis and monitoring anti-metastasis efficacy are also summarized. Finally, the current challenges and future prospects of immunological nanomaterial-based anti-metastasis are also elucidated with the intention to accelerate its clinical translation.

Added Value of Liver MRI in Patients Eligible for Surgical Resection or Ablation of Colorectal Liver Metastases Based on CT: A Systematic Review and Meta-Analysis

Background

Abdominal computed tomography (CT) is the standard imaging modality for detection and staging in patients with colorectal liver metastases (CRLM). Although liver magnetic resonance imaging (MRI) is superior to CT in detecting small lesions, guidelines are ambiguous regarding the added value of an additional liver MRI in the surgical workup of patients with CRLM. Therefore, this systematic review and meta-analysis aimed to evaluate the clinical added value of liver MRI in patients eligible for resection or ablation of CRLM based on CT.

Methods

A systematic search was performed in the PubMed, Embase, and Cochrane Library databases through June 23, 2023. Studies investigating the impact of additional MRI on local treatment plan following CT in patients with CRLM were included. Risk of bias was assessed using the QUADAS-2 tool. The pooled weighted proportions for the primary outcome were calculated using random effect meta-analysis.

Results

Overall, 11 studies with 1440 patients were included, of whom 468 patients (32.5%) were assessed for change in local treatment plan. Contrast-enhanced liver MRI was used in 10 studies, including gadoxetic acid in 9 studies. Liver MRI with diffusion-weighted imaging was used in 8 studies. Pooling of data found a 24.12% (95% confidence interval, 15.58%-32.65%) change in the local treatment plan based on the added findings of liver MRI following CT. Sensitivity analysis including 5 studies (268 patients) focusing on monophasic portal venous CT followed by gadoxetic acid-enhanced liver MRI with diffusion-weighted imaging showed a change of local treatment plan of 17.88% (95% confidence interval, 5.14%-30.62%).

Conclusions

This systematic review and meta-analysis found that liver MRI changed the preinterventional local treatment plan in approximately one-fifth of patients eligible for surgical resection or ablation of CRLM based on CT. These findings suggest a clinically relevant added value of routine liver MRI in the preinterventional workup of CRLM, which should be confirmed by large prospective studies.

MRI in addition to CT in patients scheduled for local therapy of colorectal liver metastases (CAMINO): an international, multicentre, prospective, diagnostic accuracy trial

BACKGROUND

Guidelines are inconclusive on whether contrast-enhanced MRI using gadoxetic acid and diffusion-weighted imaging should be added routinely to CT in the investigation of patients with colorectal liver metastases who are scheduled for curative liver resection or thermal ablation, or both. Although contrast-enhanced MRI is reportedly superior than contrast-enhanced CT in the detection and characterisation of colorectal liver metastases, its effect on clinical patient management is unknown. We aimed to assess the clinical effect of an additional liver contrast-enhanced MRI on local treatment plan in patients with colorectal liver metastases amenable to local treatment, based on contrast-enhanced CT.

METHODS

We did an international, multicentre, prospective, incremental diagnostic accuracy trial in 14 liver surgery centres in the Netherlands, Belgium, Norway, and Italy. Participants were aged 18 years or older with histological proof of colorectal cancer, a WHO performance status score of 0-4, and primary or recurrent colorectal liver metastases, who were scheduled for local therapy based on contrast-enhanced CT. All patients had contrast-enhanced CT and liver contrast-enhanced MRI including diffusion-weighted imaging and gadoxetic acid as a contrast agent before undergoing local therapy. The primary outcome was change in the local clinical treatment plan (decided by the individual clinics) on the basis of liver contrast-enhanced MRI findings, analysed in the intention-to-image population. The minimal clinically important difference in the proportion of patients who would have change in their local treatment plan due to an additional liver contrast-enhanced MRI was 10%. This study is closed and registered in the Netherlands Trial Register, NL8039.

FINDINGS

Between Dec 17, 2019, and July 31, 2021, 325 patients with colorectal liver metastases were assessed for eligibility. 298 patients were enrolled and included in the intention-to-treat population, including 177 males (59%) and 121 females (41%) with planned local therapy based on contrast-enhanced CT. A change in the local treatment plan based on liver contrast-enhanced MRI findings was observed in 92 (31%; 95% CI 26-36) of 298 patients. Changes were made for 40 patients (13%) requiring more extensive local therapy, 11 patients (4%) requiring less extensive local therapy, and 34 patients (11%) in whom the indication for curative-intent local therapy was revoked, including 26 patients (9%) with too extensive disease and eight patients (3%) with benign lesions on liver contrast-enhanced MRI (confirmed by a median follow-up of 21·0 months [IQR 17·5-24·0]).

INTERPRETATION

Liver contrast-enhanced MRI should be considered in all patients scheduled for local treatment for colorectal liver metastases on the basis of contrast-enhanced CT imaging.

FUNDING

The Dutch Cancer Society and Bayer AG - Pharmaceuticals.

Metachronous colorectal cancer metastasis: Who, what, when and what to do about it

Metachronous colorectal cancer (CRC) metastasis occurs due to micrometastatic disease, in up to 23% of patients who have undergone curative-intent treatment. Metachronous metastasis tends to occur within 2 years of initial treatment. Diagnosis relies on posttreatment surveillance strategies. Care for patients with metachronous CRC metastasis is complex and requires careful multidisciplinary consideration. Those with isolated and technically resectable diseases are recommended to undergo metastasectomy with adjunct chemotherapy, however, survival, even after curative-intent resection, is poor.

Can targeted nanoparticles distinguish cancer metastasis from inflammation?

Targeting ligands have been widely used to increase the intratumoral accumulation of nanoparticles and their uptake by cancer cells. However, these ligands aim at targets that are often also upregulated in inflamed tissues. Here, we assessed the ability of targeted nanoparticles to distinguish metastatic cancer from sites of inflammation. Using common targeting ligands and a 60-nm liposome as a representative nanoparticle, we generated three targeted nanoparticle (NP) variants that targeted either fibronectin, folate, or αvβ3 integrin, whose deposition was compared against that of standard untargeted NP. Using fluorescently labeled NPs and ex vivo fluorescence imaging of organs, we assessed the deposition of the NPs into the lungs of mice modeling 4 different biological landscapes, including healthy lungs, aggressive metastasis in lungs, dormant/latent metastasis in lungs, and lungs with general pulmonary inflammation. Among the four NP variants, fibronectin-targeting NP and untargeted NP exhibited the highest deposition in lungs harboring aggressive metastases. However, the deposition of all targeted NP variants in lungs with metastasis was similar to the deposition in lungs with inflammation. Only the untargeted NP was able to exhibit higher deposition in metastasis than inflammation. Moreover, flow-cytometry analysis showed all NP variants accumulated predominantly in immune cells rather than cancer cells. For example, the number of NP+ macrophages and dendritic cells was 16-fold greater than NP+ cancer cells in the case of fibronectin-targeting NP. Overall, targeted NPs were unable to distinguish cancer metastasis from general inflammation, which may have clinical implications to the nanoparticle-mediated delivery of cancer drugs.

Local Recurrences in Rectal Cancer: MRI vs. CT

Rectal cancers are often considered a distinct disease from colon cancers as their survival and management are different. Particularly, the risk for local recurrence (LR) is greater than in colon cancer. There are many factors predisposing to LR such as postoperative histopathological features or the mesorectal plane of surgical resection. In addition, the pattern of LR in rectal cancer has a prognostic significance and an important role in the choice of operative approach and. Therefore, an optimal follow up based on imaging is critical in rectal cancer. The aim of this review is to analyse the risk and the pattern of local recurrences in rectal cancer and to provide an overview of the role of imaging in early detection of LRs. We performed a literature review of studies published on Web of Science and MEDLINE up to January 2023. We also reviewed the current guidelines of National Comprehensive Cancer Network (NCCN) and the European Society for Medical Oncology (ESMO). Although the timing and the modality of follow-up is not yet established, the guidelines usually recommend a time frame of 5 years post surgical resection of the rectum. Computed Tomography (CT) scans and/or Magnetic Resonance Imaging (MRI) are the main imaging techniques recommended in the follow-up of these patients. PET-CT is not recommended by guidelines during post-operative surveillance and it is generally used for problem solving.

Left hemicolectomy and low anterior resection in colorectal cancer patients: Knight-griffen vs. transanal purse-string suture anastomosis with no-coil placement

BACKGROUND

Colorectal cancer (CRC) is considered one of the most frequent neoplasms of the digestive tract with a high mortality rate. Left hemicolectomy (LC) and low anterior resection (LAR) with minimally invasive laparoscopic and robotic approaches or with the open technique are the gold standard curative treatment.

MATERIALS AND METHODS

Seventy-seven patients diagnosed with CRC were recruited between September 2017 and September 2021. All patients underwent a preoperative staging with a full-body CT scan. The goal of this study was to compare both types of surgeries, LC-LAR LS with Knight-Griffen colorectal anastomosis and LC-LAR open with Trans-Anal Purse-String Suture Anastomosis (the TAPSSA group), by positioning a No-Coil transanal tube (SapiMed Spa, Alessandria, Italy), in terms of postoperative complications such as prolonged postoperative ileus (PPOI), anastomotic leak (AL), postoperative ileus (POI), and hospital stay.

RESULTS

The patients were divided into two groups: the first with 39 patients who underwent LC and LAR in LS with Knight-Griffen anastomosis (Knight-Griffen group) and the second with 38 patients who underwent LC and LAR by the open technique with the TAPSSA group. Only one patient who underwent the open technique suffered AL. POI was 3.76 ± 1.7 days in the TAPSSA group and 3.07 ± 1.3 days in the Knight-Griffen group. There were no statistically significant differences in terms of AL and POI between the two different groups.

CONCLUSION

The important point that preliminarily emerged from this retrospective study was that the two different techniques showed similarities in terms of AL and POI, and therefore, all the advantages reported in the previous studies pertaining to No-Coil also hold good in this study regardless of the surgical technique used. However, randomized controlled trials are needed to confirm these findings.

Optimizing Adjuvant Therapy after Surgery for Colorectal Cancer Liver Metastases: A Systematic Review

The liver is the most common site of colorectal cancer metastatic spread. Although metastasectomy is the gold standard for fit patients with resectable colorectal cancer liver metastases (CRLMs), their management after surgical treatment remains controversial. The objective of this systematic review was to collate the currently available data of the agents used in the adjuvant setting in order to define the most optimal therapeutic strategy. A systematic review of the literature was conducted by searching PubMed/Medline and Cochrane library databases. We included studies that evaluated the efficacy, the tolerability and the safety profile of various chemotherapeutic agents that are used as adjuvant treatment after surgical resection of CRLMs. The outcomes of interest were regression-free survival (RFS), disease-free survival (DFS), overall survival (OS) and severe toxicities. From 543 initial articles, 29 publications with 7028 patients were finally included. In general, the results of the eligible studies indicated that adjuvant therapy after resection of CRLMs led to improved RFS/DFS rates, but this benefit did not contribute to a statistically significant prolongation of OS. Moreover, the choice of the therapeutic strategy, namely systematic or regional chemotherapy or the combination of both, did not seem to have a differential impact on patient outcomes. However, these results should be interpreted with caution since the majority of the chosen studies are of low or moderate quality. In this context, further high-quality clinical trials conducted on patient sub-populations with modern therapies are required in order to reduce in-study and between-study heterogeneity and determine which patients are expected to derive the maximum benefit from adjuvant therapy after surgery for CRLMs.

A radiomic biomarker for prognosis of resected colorectal cancer liver metastases generalizes across MRI contrast agents

Introduction

Contrast-enhanced MRI is routinely performed as part of preoperative work-up for patients with Colorectal Cancer Liver Metastases (CRLM). Radiomic biomarkers depicting the characteristics of CRLMs in MRI have been associated with overall survival (OS) of patients, but the reproducibility and clinical applicability of these biomarkers are limited due to the variations in MRI protocols between hospitals.

Methods

In this work, we propose a generalizable radiomic model for predicting OS of CRLM patients who received preoperative chemotherapy and delayed-phase contrast enhanced (DPCE) MRIs prior to hepatic resection. This retrospective two-center study included three DPCE MRI cohorts (n=221) collected between January 2006 and December 2012. A 10-minute delayed Gd-DO3A-butrol enhanced MRI discovery cohort was used to select features based on robustness across contrast agents, correlation with OS and pairwise Pearson correlation, and to train a logistic regression model that predicts 3-year OS.

Results

The model was evaluated on a 10-minute delayed Gd-DO3A-butrol enhanced MRI validation cohort (n=121), a 20-minute delayed Gd-EOB-DTPA (n=72) cohort from the same institute, and a 5-minute delayed Gd-DTPA cohort (n=28) from an independent institute. Two features were selected: minor axis length and dependence variance. The radiomic signature model stratified high-risk and low-risk CRLM groups in the Gd-DO3Abutrol (HR = 6.29, p = .007), Gd-EOB-DTPA (HR = 3.54, p = .003) and Gd-DTPA (HR = 3.16, p = .04) validation cohorts.

Discussion

While most existing MRI findings focus on a specific contrast agent, our study shows the potential of MRI features to be generalizable across main-stream contrast agents at delayed phase.

Can optimized model-based iterative reconstruction improve the contrast of liver lesions in CT?

BACKGROUND

Computed tomography is a standard imaging procedure for the detection of liver lesions, such as metastases, which can often be small and poorly contrasted, and therefore hard to detect. Advances in image reconstruction have shown promise in reducing image noise and improving low-contrast detectability.

PURPOSE

To examine a novel, specialized, model-based iterative reconstruction (MBIR) technique for improved low-contrast liver lesion detection.

MATERIAL AND METHODS

Patient images with reported poorly contrasted focal liver lesions were retrospectively reconstructed with the low-contrast attenuating algorithm (FIRST-LCD) from primary raw data. Liver-to-lesion contrast, signal-to-noise, and contrast-to-noise ratios for background and liver noise for each lesion were compared for all three FIRST-LCD presets with the established hybrid iterative reconstruction method (AIDR-3D). An additional visual conspicuity score was given by two experienced radiologists for each lesion.

RESULTS

A total of 82 lesions in 57 examinations were included in the analysis. All three FIRST-LCD algorithms provided statistically significant increases in liver-to-lesion contrast, with FIRST_MILD showing the largest increase (40.47 HU in AIDR-3D; 45.84 HU in FIRST_MILD; P < 0.001). Substantial improvement was shown in contrast-to-noise metrics. Visual analysis of the lesions shows decreased lesion visibility with all FIRST methods in comparison to AIDR-3D, with FIRST_STR showing the closest results (P < 0.001).

CONCLUSION

Objective image metrics show promise for MBIR methods in improving the detectability of low-contrast liver lesions; however, subjective image quality may be perceived as inferior. Further improvements are necessary to enhance image quality and lesion detection.

Real-Time Split-Dose PET/CT-Guided Ablation Improves Colorectal Liver Metastasis Detection and Ablation Zone Margin Assessments without the Need for Repeated Contrast Injection

BACKGROUND

Real-time split-dose PET can identify the targeted colorectal liver metastasis (CLM) and eliminate the need for repeated contrast administration before and during thermal ablation (TA). This study aimed to assess the added value of pre-ablation real-time split-dose PET when combined with non-contract CT in the detection of CLM for ablation and the evaluation of the ablation zone and margins.

METHODS

A total of 190 CLMs/125 participants from two IRB-approved prospective clinical trials using PET/CT-guided TA were analyzed. Based on detection on pre-TA imaging, CLMs were categorized as detectable, non-detectable, and of poor conspicuity on CT alone, and detectable, non-detectable, and low FDG-avidity on PET/CT after the initial dose. Ablation margins around the targeted CLM were evaluated using a 3D volumetric approach.

RESULTS

We found that 129/190 (67.9%) CLMs were detectable on CT alone, and 61/190 CLMs (32.1%) were undetectable or of poor conspicuity, not allowing accurate depiction and targeting by CT alone. Thus, the theoretical 5- and 10-mm margins could not be defined in these tumors (32.1%) using CT alone. When TA intraprocedural PET/CT images are obtained and inspected (fused PET/CT), only 4 CLM (2.1%) remained undetectable or had a low FDG avidity.

CONCLUSIONS

The addition of PET to non-contrast CT improved CLM detection for ablation targeting, margin assessments, and continuous depiction of the FDG avid CLMs during the ablation without the need for multiple intravenous contrast injections pre- and intra-procedurally.

Surgical Management of Liver Metastases from Colorectal Cancer: A Single-Surgeon Preliminary Findings Report

Introduction: Colorectal cancer is a significant medical and social problem. Approximately half of the patients with colorectal carcinoma develop liver metastasis. Most commonly, they are identified during the diagnostic process or the initial surgery. After the diagnostics, only 15% of the cases are referred to receive radical surgery. Liver resection in patients with hepatic metastases is the only way to improve their survival. Objective: To introduce a surgical strategy used for the treatment of colorectal liver metastases. Materials and Methods: The study included 539 patients who underwent surgery for colorectal carcinoma in the Department of Surgery at University Hospital "Kaspela" during the period 2014–2020. This data was collected from the patients' disease history. Results: Of the 539 patients with colorectal carcinoma, 74 (13.7%) were diagnosed with synchronous liver metastases. In 38 (51.3%) of the cases, the metastases were solitary, of which 21 were removed simultaneously and 17 at the follow-up stage. In 8 (10.8%) cases, more than one (2 to 3) solitary metastasis was established near the edges. They were also removed simultaneously. In 6 patients (8.1%), bi-lobar and peripherally localized solitary lesions were found, which were removed instantly and chemotherapy was administered. In 22 (29.7%) of the patients with multiple bi-lobar metastases, only a biopsy was performed, and surgery was carried out only in those affected by chemotherapy. Conclusion: The possibilities of simultaneous and stepwise liver resections were expanded by focusing on individual approach preferences and improving diagnostic methods, liver surgery techniques, and modern chemotherapy. This increased the survival rate of patients with colorectal liver metastases.

NGA-Inspired Nanorobots-Assisted Detection of Multifocal Cancer

We propose a new framework of computing-inspired multifocal cancer detection procedure (MCDP). Under the rubric of MCDP, the tumor foci to be detected are regarded as solutions of the objective function, the tissue region around the cancer areas represents the parameter space, and the nanorobots loaded with contrast medium molecules for cancer detection correspond to the optimization agents. The process that the nanorobots detect tumors by swimming in the high-risk tissue region can be regarded as the process that the agents search for the solutions of an objective function in the parameter space with some constraints. For multimodal optimization (MMO) aiming to locate multiple optimal solutions in a single simulation run, the niche technology has been widely used. Specifically, the niche genetic algorithm (NGA) has been shown to be particularly effective in solving MMO. It can be used to identify the global optima of multiple hump functions in a running, effectively keep the diversity of the population, and prematurely avoid the genetic algorithm. Learning from the optimization procedure of NGA, we propose the NGA-inspired MCDP in order to locate the tumor targets efficiently while taking into account realistic in vivo propagation and controlling of nanorobots, which is different from the use scenario of the standard NGA. To improve the performance of the MCDP, we also modify the crossover operator of the original NGA from crossing within a population to crossing between two populations. Finally, we present comprehensive numerical examples to demonstrate the effectiveness of the NGA-inspired MCDP when the biological objective function is associated with the blood flow velocity profile caused by tumor-induced angiogenesis.

Hepatic Positron Emission Tomography: Applications in Metabolism, Haemodynamics and Cancer

Evaluating in vivo the metabolic rates of the human liver has been a challenge due to its unique perfusion system. Positron emission tomography (PET) represents the current gold standard for assessing non-invasively tissue metabolic rates in vivo. Here, we review the existing literature on the assessment of hepatic metabolism, haemodynamics and cancer with PET. The tracer mainly used in metabolic studies has been [¹⁸F]2-fluoro-2-deoxy-D-glucose (¹⁸F-FDG). Its application not only enables the evaluation of hepatic glucose uptake in a variety of metabolic conditions and interventions, but based on the kinetics of ¹⁸F-FDG, endogenous glucose production can also be assessed. 14(R,S)-[¹⁸F]fluoro-6-thia-Heptadecanoic acid (¹⁸F-FTHA), ¹¹C-Palmitate and ¹¹C-Acetate have also been applied for the assessment of hepatic fatty acid uptake rates (¹⁸F-FTHA and ¹¹C-Palmitate) and blood flow and oxidation (¹¹C-Acetate). Oxygen-15 labelled water (¹⁵O-H₂O) has been used for the quantification of hepatic perfusion. ¹⁸F-FDG is also the most common tracer used for hepatic cancer diagnostics, whereas ¹¹C-Acetate has also shown some promising applications in imaging liver malignancies. The modelling approaches used to analyse PET data and also the challenges in utilizing PET in the assessment of hepatic metabolism are presented.

Respiratory 4D-Gating F-18 FDG PET/CT Scan for Liver Malignancies: Feasibility in Liver Cancer Patient and Tumor Quantitative Analysis

Purpose

To evaluate the potential clinical role and effectiveness of respiratory 4D-gating F-18 FDG PET/CT scan for liver malignancies, relative to routine (3D) F-18 FDG PET/CT scan.

Materials and Methods

This study presented a prospective clinical study of 16 patients who received F-18 FDG PET/CT scan for known or suspected malignant liver lesions. Ethics approvals were obtained from the ethics committees of the Hong Kong Baptist Hospital and The Hong Kong Polytechnic University. Liver lesions were compared between the gated and ungated image sets, in terms of 1) volume measurement of PET image, 2) accuracy of maximum standardized uptake value (SUV_max), mean standardized uptake value (SUV_mean), and 3) accuracy of total lesion glycoses (TLG). Statistical analysis was performed by using a two-tailed paired Student t-test and Pearson correlation test.

Results

The study population consisted of 16 patients (9 males and 7 females; mean age of 65) with a total number of 89 lesions. The SUV_max and SUV_mean measurement of the gated PET images was more accurate than that of the ungated PET images, compared to the static reference images. An average of 21.48% (p < 0.001) reduction of the tumor volume was also observed. The SUV_max and SUV_mean of the gated PET images were improved by 19.81% (p < 0.001) and 25.53% (p < 0.001), compared to the ungated PET images.

Conclusions

We have demonstrated the feasibility of implementing 4D PET/CT scan for liver malignancies in a prospective clinical study. The 4D PET/CT scan for liver malignancies could improve the quality of PET image by improving the SUV accuracy of the lesions and reducing image blurring. The improved accuracy in the classification and identification of liver tumors with 4D PET image would potentially lead to its increased utilization in target delineation of GTV, ITV, and PTV for liver radiotherapy treatment planning in the future.

Role of CT in Two-Stage Liver Surgery

Complete resection is the only potentially curative treatment for primary or metastatic liver tumors. Improvements in surgical techniques such as conventional two-stage hepatectomy (TSH) with portal vein embolization and ALPPS (associating liver partition and portal vein ligation for staged hepatectomy) promote hypertrophy of the future liver remnant (FLR), expanding resection criteria to include patients with widespread hepatic disease who were formerly not considered candidates for resection. Radiologists are essential in the multidisciplinary approach required for TSH. In particular, multidetector CT has a critical role throughout the various stages of this surgical process. The aims of CT before the first stage of TSH are to define the feasibility of surgery, assess the number and location of liver tumors in relation to relevant anatomy, and provide a detailed anatomic evaluation, including vascular and biliary variants. Volume calculation with CT is also essential to determine if the FLR is sufficient to avoid posthepatectomy liver failure. The objectives of CT between the first and second stages of TSH are to recalculate liver volumes (ie, assess FLR hypertrophy) and depict expected liver changes and complications that could modify the surgical plan or preclude the second stage of definitive resection. In this review, the importance of CT throughout different stages of TSH is discussed and key observations that contribute to surgical planning are highlighted. In addition, the advantages and limitations of MRI for detection of liver metastases and assessment of complications are briefly described. ^©RSNA, 2022.

Intraoperative (Contrast-Enhanced) Ultrasound Has the Highest Diagnostic Accuracy of Any Imaging Modality in Resection of Colorectal Liver Metastases

AIM

Defining sensitivity, specificity, diagnostic accuracy for detection of colorectal liver metastases in imaging compared to intraoperative assessment. Defining a cutoff, where accuracy of detection is impaired.

METHODS

Prospective single-institution clinical trial (clinicaltrials.gov: NCT01522209). Patients underwent CEUS, MDCT, and 3 Tesla EOB-MRI within 2 weeks preoperatively. Intraoperative palpation, IOUS, and CEIOUS were performed. A patient and lesion-based database was analyzed for accuracy of detection of CEUS, CT, MRI, and Palp/IOUS/CEIOUS combined read. Histology was standard of reference.

RESULTS

Forty-seven high tumor load (mean 5, 4 lesions) patients were analyzed. Histopathology confirmed 264 lesions (245 malignant: 19 benign). Accuracy for detection of all lesions: CEUS 63%, CT 71%, MRI 92%, and PALP/IOUS/CEIOUS 98%. ROC analysis for lesion size showed severe impairment of accuracy in lesion detection smaller than 5mm. Intraoperative imaging was not impaired by lesion size. Patient-based analysis revealed a change of resection plan after IOUS/CEIOUS in 35% of patients.

CONCLUSION

At 5-mm lesion size, preoperative imaging shows a drop in accuracy of detection. In patients with multiple lesions, addition of MRI to MDCT seems useful. Accuracy of intraoperative ultrasound is not impacted by lesion size and should be mandatory. CEIOUS can improve intraoperative decision-making.

TRIAL REGISTRATION

Study registered with clinicaltrials.gov : NCT01522209.

Clinical added value of MRI to CT in patients scheduled for local therapy of colorectal liver metastases (CAMINO): study protocol for an international multicentre prospective diagnostic accuracy study

BACKGROUND

Abdominal computed tomography (CT) is the standard imaging method for patients with suspected colorectal liver metastases (CRLM) in the diagnostic workup for surgery or thermal ablation. Diffusion-weighted and gadoxetic-acid-enhanced magnetic resonance imaging (MRI) of the liver is increasingly used to improve the detection rate and characterization of liver lesions. MRI is superior in detection and characterization of CRLM as compared to CT. However, it is unknown how MRI actually impacts patient management. The primary aim of the CAMINO study is to evaluate whether MRI has sufficient clinical added value to be routinely added to CT in the staging of CRLM. The secondary objective is to identify subgroups who benefit the most from additional MRI.

METHODS

In this international multicentre prospective incremental diagnostic accuracy study, 298 patients with primary or recurrent CRLM scheduled for curative liver resection or thermal ablation based on CT staging will be enrolled from 17 centres across the Netherlands, Belgium, Norway, and Italy. All study participants will undergo CT and diffusion-weighted and gadoxetic-acid enhanced MRI prior to local therapy. The local multidisciplinary team will provide two local therapy plans: first, based on CT-staging and second, based on both CT and MRI. The primary outcome measure is the proportion of clinically significant CRLM (CS-CRLM) detected by MRI not visible on CT. CS-CRLM are defined as liver lesions leading to a change in local therapeutical management. If MRI detects new CRLM in segments which would have been resected in the original operative plan, these are not considered CS-CRLM. It is hypothesized that MRI will lead to the detection of CS-CRLM in ≥10% of patients which is considered the minimal clinically important difference. Furthermore, a prediction model will be developed using multivariable logistic regression modelling to evaluate the predictive value of patient, tumor and procedural variables on finding CS-CRLM on MRI.

DISCUSSION

The CAMINO study will clarify the clinical added value of MRI to CT in patients with CRLM scheduled for local therapy. This study will provide the evidence required for the implementation of additional MRI in the routine work-up of patients with primary and recurrent CRLM for local therapy.

TRIAL REGISTRATION

The CAMINO study was registered in the Netherlands National Trial Register under number NL8039 on September 20th 2019.

Missing colorectal liver metastases: the surgical challenge

BACKGROUND

New chemotherapy schemes have allowed for a better radiological response of unresectable colorectal liver metastases, leading to an interesting scenario known as a complete radiological response. The aim of this study was to review the current management of missing liver metastases (MLM) from the liver surgeon's point of view.

METHODS

A systematic search was conducted on all publications of PubMed and Embase between 2003 and 2018. Meta-analysis was performed on MLM resected/unresected. Residual tumor or regrowth and relapse-free survival were used as evaluation indices.

RESULTS

After literature search, 18 original articles were included for analysis. The predictive factors for MLM are type and duration of chemotherapy and size and number of lesions. Magnetic resonance is the most sensitive preoperative technique. Regarding clinical management, liver surgery is deemed the fundamental pillar in the therapeutic strategy of these patients. Meta-analysis due to data heterogeneity was inconclusive.

CONCLUSIONS

Depending on the clinical context, MLM monitoring appears to be a valid therapeutic alternative. Nevertheless, prospective randomized clinical studies are needed.

Evaluation of the Diagnostic Performance of Positron Emission Tomography/Magnetic Resonance for the Diagnosis of Liver Metastases

OBJECTIVE

The aim of this study was to compare the performance of positron emission tomography (PET)/magnetic resonance (MR) versus stand-alone PET and stand-alone magnetic resonance imaging (MRI) in the detection and characterization of suspected liver metastases.

MATERIALS AND METHODS

This multi-institutional retrospective performance study was approved by the institutional review boards and was Health Insurance Portability and Accountability Act compliant, with waiver of informed consent. Seventy-nine patients with confirmed solid extrahepatic malignancies who underwent upper abdominal PET/MR between February 2017 and June 2018 were included. Where focal hepatic lesions were identified, the likelihood of a diagnosis of a liver metastasis was defined on an ordinal scale for MRI, PET, and PET/MRI by 3 readers: 1 nuclear medicine physician and 2 radiologists. The number of lesions per patient, lesion size, and involved hepatic segments were recorded. Proof of metastases was based on histopathologic correlation or clinical/imaging follow-up. Diagnostic performance was assessed using sensitivity, specificity, positive and negative predictive values, and receiver operator characteristic curve analysis.

RESULTS

A total of 79 patients (53 years, interquartile range, 50-68; 43 men) were included. PET/MR had a sensitivity of 95%, specificity of 97%, positive predictive value of 97%, and negative predictive value of 95%. The sensitivity, specificity, positive predictive value, and negative predictive value of MRI were 88%, 98%, 98%, and 90% and for PET were 83%, 97%, 97%, and 86%, respectively. The areas under the curve for PET/MRI, MRI, and PET were 95%, 92%, and 92%, respectively.

CONCLUSIONS

Contrast-enhanced PET/MR has a higher sensitivity and negative predictive value than either PET or MRI alone in the setting of suspected liver metastases. Fewer lesions were characterized as indeterminate by PET/MR in comparison with PET and MRI. This superior performance could potentially impact treatment and management decisions for patients with suspected liver metastases.

Distinguishing pure histopathological growth patterns of colorectal liver metastases on CT using deep learning and radiomics: a pilot study

Histopathological growth patterns (HGPs) are independent prognosticators for colorectal liver metastases (CRLM). Currently, HGPs are determined postoperatively. In this study, we evaluated radiomics for preoperative prediction of HGPs on computed tomography (CT), and its robustness to segmentation and acquisition variations. Patients with pure HGPs [i.e. 100% desmoplastic (dHGP) or 100% replacement (rHGP)] and a CT-scan who were surgically treated at the Erasmus MC between 2003-2015 were included retrospectively. Each lesion was segmented by three clinicians and a convolutional neural network (CNN). A prediction model was created using 564 radiomics features and a combination of machine learning approaches by training on the clinician's and testing on the unseen CNN segmentations. The intra-class correlation coefficient (ICC) was used to select features robust to segmentation variations; ComBat was used to harmonize for acquisition variations. Evaluation was performed through a 100 × random-split cross-validation. The study included 93 CRLM in 76 patients (48% dHGP; 52% rHGP). Despite substantial differences between the segmentations of the three clinicians and the CNN, the radiomics model had a mean area under the curve of 0.69. ICC-based feature selection or ComBat yielded no improvement. Concluding, the combination of a CNN for segmentation and radiomics for classification has potential for automatically distinguishing dHGPs from rHGP, and is robust to segmentation and acquisition variations. Pending further optimization, including extension to mixed HGPs, our model may serve as a preoperative addition to postoperative HGP assessment, enabling further exploitation of HGPs as a biomarker.

The Correlation between 18F-FDG PET/CT Imaging SUVmax of Preoperative Colon Cancer Primary Lesions and Clinicopathological Factors

Background

The purpose of this study is to explore the correlation between the ¹⁸F-FDG PET/CT imaging maximum standardized uptake value (SUVmax) of preoperative colon cancer primary lesions and clinicopathological factors.

Methods

88 colon cancer patients diagnosed by histopathology were collected from January 2014 to December 2015. ¹⁸F-FDG PET/CT imaging was performed before surgery. Kaplan–Meier survival analysis was used to assess the prognosis of colon cancer patients.

Results

The ¹⁸F-FDG PET/CT imaging SUVmax value of preoperative colon cancer primary lesion was significantly correlated with the length of the lesion, clinical stage, histopathological type, and the degree of tumor differentiation. The SUVmax value of tumors with long-diameter, ≥ 3 cm, clinically high-stage, adenocarcinoma, and poorly differentiated lesions was significantly high. In addition, the consistency between PET/CT and surgical pathological results at stage I and IV was higher. Stage II and III PET/CT are basically consistent with the pathological results of surgery. Kaplan–Meier survival analysis showed that the 5-year event-free survival rate of the SUVmax > 18.26 group was significantly lower than that of the SUVmax ≤ 18.26 group.

Conclusion

¹⁸F-FDG PET/CT imaging SUVmax of preoperative colon cancer primary lesions can not only reflect the proliferation and invasion ability but also monitor the recurrence and metastasis of colon cancer.

Rim enhancement on hepatobiliary phase of pre-treatment 3.0 T MRI: A potential marker for early chemotherapy response in colorectal liver metastases treated with XELOX

PURPOSE

To assess the value of the enhanced features on the hepatobiliary phase (HBP) of pre-treatment Gd-EOB-DTPA MRI in evaluating response to chemotherapy in colorectal liver metastases (CRLMs).

METHODS

We retrospectively studied 65 patients with CRLMs who underwent Gd-EOB-DTPA enhanced MRI before chemotherapy from October 2015 to November 2017. The diagnosis of liver metastasis was established on the basis of imaging findings. Two radiologists evaluated the size, contrast-enhanced (CE) patterns of the maximum lesion on the HBP. According to the different CE patterns, we quantified area signal intensity (SI) by applying SI ratio (such as SI_center/outer and SI_rim/center). All of the above parameters were analyzed in terms of chemotherapy response.

RESULTS

Rim enhancement on the HBP was more frequent in the responding group of 28 patients (72%) than in the non-responding group of eight patients (31%). Additionally, there was a significant association between chemotherapy response and quantitative parameters: including diameter (P = 0.04), SI_center/outer (P = 0.047) and SI_rim/center (P = 0.012). The HBP CE pattern (P = 0.007) and SI_center/outer (P = 0.022) were independent factors for chemotherapy response. The areas under the curve (AUCs) of the above-mentioned parameters were significant associated with response to chemotherapy, in which diameter, HBP CE patterns, SI_center/outer, and SI_rim/center were 0.638, 0.706, 0.712, and 0.673, respectively. Moreover, the combination of these parameters obtained the largest AUC of 0.821.

CONCLUSION

The CE patterns, in particular with rim enhancement, and SI ratio parameters on the HBP are useful indicators for early evaluation of therapeutic response after chemotherapy in patients with CRLMs.

Endoscopic Ultrasound for Detection of Liver Metastasis: Hope or Hype?

Transabdominal ultrasonography, contrast-enhanced computed tomography, and magnetic resonance imaging (MRI) are the common diagnostic tests for the detection of hepatic lesions. Use of enhanced and advanced MRI technique, that is, diffusion weighted MRI and hepatocyte-specific contrast agents, has further improved the accuracy of detection of metastatic liver lesions ≤10 mm in diameter. However, even with these advanced imaging modalities sensitivity is low for lesions smaller than 10 mm when compared with standard intraoperative ultrasound. Endoscopic ultrasound (EUS) is an emerging imaging modality with resolution sufficient to detect and sample lesions as small as 5 mm in diameter. In this news and views, we have discussed the role of standard and enhanced EUS for the detection of metastatic liver lesions.

The Diagnostic Value of FDG-PET/CT for Urachal Cancer

BACKGROUND

Urachal carcinoma (UrC) is a rare malignancy that often presents at an advanced stage with metastases in up to a quarter of patients. There is no consensus on the optimal form of staging for patients with UrC. In the present study, we evaluated the diagnostic value of ¹⁸F-fluorodeoxyglucose-positron emitted tomography/computed tomography (FDG-PET/CT) for UrC.

PATIENTS AND METHODS

We evaluated 40 consecutive patients who were staged for urachal cancer between 2010 and 2020. They underwent a total of 62 FDG-PET/CTs (40 for primary staging, and 22 during follow-up), which were compared with standard-of-care contrast-enhanced CT (CECT). The metabolic detection of primary tumors, lymph node metastases (LNMs), peritoneal metastases (PMs), distant metastases (DMs), and local recurrence by FDG-PET/CT was evaluated. Sensitivity and specificity were calculated compared with CECT. Histopathology or follow-up imaging was the reference standard.

RESULTS

Of all 40 patients, 33 patients (83%) had urachal adenocarcinoma-26 (65%) with a mucinous component and 7 (17%) with invasive urothelial carcinoma. All local UrC tumors could be visualized on CT, and 80% showed increased FDG uptake. At initial staging, FDG-PET/CT detected FDG-avid LNMs, PMs, and DMs in 50%, 17%, and 25% of patients, respectively. These metastases were also visualized on CECT. During follow up, FDG-PET/CT revealed FDG-avid local recurrences that were not seen on CT in two out of eight patients (25%).

CONCLUSION

The present study demonstrates that most UrC can be visualized on FDG-PET/CT. At initial diagnosis, FDG-PET/CT does not seem to yield additional information compared with CECT; however, FDG-PET/CT may be helpful during follow-up. This is a small study, and the findings should be corroborated with larger series.

Imaging of colorectal cancer liver metastases using contrast-enhanced US, multidetector CT, MRI, and FDG PET/CT: a meta-analysis

BACKGROUND

Imaging of colorectal cancer liver metastases (CRCLMs) has improved in recent years. Therefore, the role of current imaging techniques needs to be defined.

PURPOSE

To assess the diagnostic performance of contrast-enhanced ultrasound (CEUS), multidetector computed tomography (MDCT), magnetic resonance imaging (MRI), and fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT in the detection of CRCLMs.

MATERIAL AND METHODS

PubMed database was searched for articles published during 2000-2019. Inclusion criteria were as follows: diagnosis/suspicion of CRCLMs; CEUS, MDCT, MRI, or FDG PET/CT performed for the detection of CRCLMs; prospective study design; histopathologic examination, intraoperative findings and/or follow-up used as reference standard; and data for calculating sensitivity and specificity reported.

RESULTS

Twelve prospective studies were assessed, including 536 patients with CRCLMs (n = 1335). On a per-lesion basis, the sensitivity of CEUS, MDCT, MRI, and FDG PET/CT was 86%, 84%, 89%, and 62%, respectively. MRI had the highest sensitivity on a per-lesion analysis. CEUS and MDCT had comparable sensitivities. On a per-patient basis, the sensitivity and specificity of CEUS, MDCT, MRI, and FDG PET/CT was 80% and 97%, 87% and 95%, 87% and 94%, and 96% and 97%, respectively. The per-patient sensitivities for MRI and MDCT were similar. The sensitivity for MRI was higher than that for CEUS, MDCT, and FDG PET/CT for lesions <10 mm and lesions at least 10 mm in size. Hepatospecific contrast agent did not improve diagnostic performances.

CONCLUSION

MRI is the preferred imaging modality for evaluating CRCLMs. Both MDCT and CEUS can be used as alternatives.

Contrast-enhanced ultrasound can guide the therapeutic strategy by improving the detection of colorectal liver metastases

BACKGROUND & AIMS

CT may miss up to 30% of cases of colorectal liver metastases (CRLMs). We assessed the impact of contrast-enhanced ultrasound (CEUS) on the detection of CRLMs and on changes to the therapeutic strategy; additionally, we assessed the accuracy of CEUS in differentiating unclear focal liver lesions (FLLs) compared to staging-CT.

METHODS

We prospectively analyzed all patients with newly diagnosed and histologically confirmed colorectal cancer (CRC) at our tertiary gastroenterological center between December 2015 and May 2019. CEUS was performed in a total of 296 patients without CRLMs after staging-CT using the contrast agent (SonoVue®). Standard of reference was obtained by MRI or histology to diagnose CRLMs missed by CT. Benign FLLs were confirmed by MRI or follow-up CT (mean follow-up interval: 18 months).

RESULTS

Eight additional CRLMs were detected by CEUS (overall 2.7%; sensitivity 88.9%, specificity 99.0%, positive predictive value 100%, negative predictive value 99.6%). All patients with CRLMs detected only by CEUS were in tumor stage T3/T4 (4.0% additionally detected CRLMs). The number needed to screen to detect 1 additional CRLM by CEUS was 37 in all patients and 24.5 in T3/T4-patients. When results were reviewed by a board-certified radiologist and oncologist, the therapeutic strategy changed in 6 of these 8 patients. Among the 62 patients (20.9%) with unclear FLLs after staging-CT, CEUS determined the dignity (malignant vs. benign) of 98.4% of the FLLs.

CONCLUSION

Overall, CEUS detected 2.7% additional CRLMs (including 4.0% in tumor stage T3/T4) with a significant impact on the oncological therapeutic strategy for 75% of these patients. Patients with tumor stage T3/T4 would particularly benefit from CEUS. We propose CEUS as the first imaging modality for CT-detected lesions of unknown dignity.

LAY SUMMARY

In patients with newly diagnosed colorectal cancer, contrast-enhanced ultrasound (CEUS) detected additional liver metastases after computed tomography (CT). In the majority of these patients, the oncological therapy was changed after obtaining the CEUS results. After staging-CT, 21% of hepatic lesions remained unclear. In these cases, CEUS was accurate to either reveal or exclude liver metastasis in nearly all patients and could reduce costs (e.g., number of MRI scans).

Is It Time to Introduce PET/CT in Rectal Cancer Guidelines?

At the moment, international guidelines for rectal cancer suggest to consider F-FDG PET/CT scan in a few conditions: (1) at disease presentation in case of suspected or proven metastatic synchronous adenocarcinoma with potentially curable M1 disease; (2) in the recurrence workup for serial carcinoembryonic antigen level elevation; (3) in the recurrence workup with metachronous metastases documented by CT, MRI, or biopsy; (4) in case of strong contraindication to IV contrast agent administration; and (5) to evaluate an equivocal finding on a contrast-enhanced CT or MRI. PET/CT is not indicated in the follow-up or surveillance of rectal cancer. On the other hand, an attentive evaluation of the literature shows that PET/CT may also be used in some circumstances with significant levels of diagnostic accuracy. This review article aims to emphasize differences between current international guidelines and scientific literature in the role of PET/CT in rectal cancer.

Imaging in disappearing colorectal liver metastases and their accuracy: a systematic review

Background

Approximately 30% of patients with colorectal cancer develop colorectal liver metastases (CRLM). CRLM that become undetectable by imaging after chemotherapy are called disappearing liver metastases (DLM). But a DLM is not necessarily equal to cure. An increasing incidence of patients with DLM provides surgeons with a difficult dilemma: to resect or to not resect the original sites of DLM? The aim of this review was to investigate to what extent a DLM equates a complete response (CR) and to compare outcomes.

Methods

This review was conducted in accordance with the PRISMA guidelines and registered in Prospero (registration number CRD42017070441). Literature search was made in the PubMed and Embase databases. During the process of writing, PubMed was repeatedly searched and reference lists of included studies were screened for additional studies of interest for this review. Results were independently screened by two authors with the Covidence platform. Studies eligible for inclusion were those reporting outcomes of DLM in adult patients undergoing surgery following chemotherapy.

Results

Fifteen studies were included with a total of 2955 patients with CRLM. They had 4742 CRLM altogether. Post-chemotherapy, patients presented with 1561 DLM. Patients with one or more DLM ranged from 7 to 48% (median 19%). Median DLM per patient was 3.4 (range 0.4–5.6). Patients were predominantly evaluated by contrast-enhanced computed tomography (CE-CT) before and after chemotherapy, with some exceptions and with addition of magnetic resonance imaging (MRI) in some studies. Intraoperative ultrasound (IOUS) was universally performed in all but two studies. If a DLM remained undetectable by IOUS, this DLM represented a CR in 24–96% (median 77.5%). Further, if a DLM on preoperative CE-CT remained undetectable by additional workup with MRI and CE-IOUS, this DLM was equal to a CR in 75–94% (median 89%). Patients with resected DLM had a longer disease-free survival compared to patients with DLM left in situ but statistically significant differences in overall survival could not be found.

Conclusion

Combination of CE-CT, MRI, and IOUS showed promising results in accurately identifying DLM with CR. This suggests that leaving DLM in situ could be an alternative to surgical resection when a DLM remains undetectable by MRI and IOUS.

Molecular Imaging and Therapy of Colorectal and Anal Cancer

Colorectal cancer is the cancer with the third highest incidence both in males and females in the USA and is also frequently occurring in other industrialized nations. Anal cancer on the other hand is much rarer, but has a rising incidence, especially in high income nations and with a connection to HIV infections, homosexual men and a younger age of the first sexual encounter. Both have high mortality rates in common and are complex to handle in terms of prevention, staging, treatment and diagnostic of recurrence. This article aims to give an overview about the established diagnostic methods of nuclear medicine, especially sole PET and (contrast enhanced) hybrid imaging with 18F-FDG as tracer for primary staging, restaging, therapy monitoring and radiotherapy planning in current guidelines, with a special focus on the American guidelines of the National Comprehensive Cancer Network for colorectal and anal cancer. There will also be an outlook on potential future adjustments in those leading to a more significant representation of nuclear medicine by giving a synopsis of the available studies and data published in international medical press. New tracers that are still in research stage, progress in the imaging techniques, for example a further establishment of PET/MR hybrid imaging, the use of artificial intelligence and parametric imaging, as well as possible future theranostic applications like c-MET binding peptides will also be shortly discussed.

Molecular Imaging and Therapy of Liver Tumors

Liver cancer is one of the top leading causes of mortality worldwide. Conventional imaging using contrast enhanced CT and MRI are currently the mainstay of oncologic imaging of the liver for the diagnosis and management of cancer. In the past two decades, especially since the advent of hybrid imaging in the form of PET/CT and SPECT/CT, molecular imaging has been increasingly utilized for oncologic imaging and the variety of radionuclide probes for imaging liver cancers have been expanding. Beyond the usual workhorse of FDG as an oncologic tracer, there is a growing body of evidence showing that radiolabeled choline tracers, C-11 acetate and other new novel tracers may have increasing roles to play for the imaging of liver tumors. On the therapy front, there have also been advances in recent times in terms of targeted therapies for both primary and secondary liver malignancies, particularly with transarterial radioembolization. The concept of theranostics can be applied to transarterial radioembolization by utilizing a pretreatment planning scan, such as Tc-99m macroaggregated albumin scintigraphy, coupled with post treatment imaging. Radiation dose planning by personalized dosimetric calculations to the liver tumors is also being advocated. This article explores the general trends in the field of nuclear medicine for the imaging and treatment of liver cancer above and beyond routine diagnosis and management.

Follow-Up 18F-FDG PET/CT versus Contrast-Enhanced CT after Ablation of Liver Metastases of Colorectal Carcinoma-A Cost-Effectiveness Analysis

PURPOSE

After a percutaneous ablation of colorectal liver metastases (CRLM), follow-up investigations to evaluate potential tumor recurrence are necessary. The aim of this study was to analyze whether a combined 18F-Fluordesoxyglucose positron emission tomography-computed tomography (18F-FDG PET/CT) scan is cost-effective compared to a contrast-enhanced computed tomography (CE-CT) scan for detecting local tumor progression.

MATERIALS AND METHODS

A decision model based on Markov simulations that estimated lifetime costs and quality-adjusted life years (QALYs) was developed. Model input parameters were obtained from the recent literature. Deterministic sensitivity analysis of diagnostic parameters based on a Monte-Carlo simulation with 30,000 iterations was performed. The willingness-to-pay (WTP) was set to $100,000/QALY.

RESULTS

In the base-case scenario, CE-CT resulted in total costs of $28,625.08 and an efficacy of 0.755 QALYs, whereas 18F-FDG PET/CT resulted in total costs of $29,239.97 with an efficacy of 0.767. Therefore, the corresponding incremental cost-effectiveness ratio (ICER) of 18F-FDG PET/CT was $50,338.96 per QALY indicating cost-effectiveness based on the WTP threshold set above. The results were stable in deterministic and probabilistic sensitivity analyses.

CONCLUSION

Based on our model, 18F-FDG PET/CT can be considered as a cost-effective imaging alternative for follow-up investigations after percutaneous ablation of colorectal liver metastases.

Does Routine Triple-Time-Point FDG PET/CT Imaging Improve the Detection of Liver Metastases?

Prior reports have demonstrated the improved ability of delayed fluorine-18 (¹⁸F) fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) imaging (dual-time-point imaging) in detecting more patients with liver metastases. To evaluate whether routine triple-time-point FDG PET/CT imaging improves the detection of liver metastasis not visualized on initial imaging. To our knowledge, no triple-time-point imaging has been reported. This retrospective study included total 310 patients with various malignancies who underwent PET/CT scans. Triple-time-point imaging including the liver was obtained. The comparison between negative and positive liver lesions on delayed imaging for patients with initial negative imaging were analyzed. Of the 310 patients, 286 did not exhibit liver lesions on initial imaging, but six of the 286 patients exhibited lesions on delayed imaging. No additional liver lesions were detected on further delayed imaging in the 286 patients. The other 24 patients with liver lesions identified on initial imaging still showed lesions on delayed and further delayed imaging. The analysis showed a significant difference in the percentage of colorectal cancer (66.7%) and liver lesions before the PET scan (50.0%) compared with unchanged results (22.1% and 3.9%, respectively). Routine triple-time-point imaging did not improve the detection of liver metastases; however, it may be recommended in patients with colorectal cancer and liver lesions before the PET scan.

Search of low-contrast liver lesions in abdominal CT: the importance of scrolling behavior

Purpose: Visual search using volumetric images is becoming the standard in medical imaging. However, we do not fully understand how eye movement strategies mediate diagnostic performance. A recent study on computed tomography (CT) images showed that the search strategies of radiologists could be classified based on saccade amplitudes and cross-quadrant eye movements [eye movement index (EMI)] into two categories: drillers and scanners. Approach: We investigate how the number of times a radiologist scrolls in a given direction during analysis of the images (number of courses) could add a supplementary variable to use to characterize search strategies. We used a set of 15 normal liver CT images in which we inserted 1 to 5 hypodense metastases of two different signal contrast amplitudes. Twenty radiologists were asked to search for the metastases while their eye-gaze was recorded by an eye-tracker device (EyeLink1000, SR Research Ltd., Mississauga, Ontario, Canada). Results: We found that categorizing radiologists based on the number of courses (rather than EMI) could better predict differences in decision times, percentage of image covered, and search error rates. Radiologists with a larger number of courses covered more volume in more time, found more metastases, and made fewer search errors than those with a lower number of courses. Our results suggest that the traditional definition of drillers and scanners could be expanded to include scrolling behavior. Drillers could be defined as scrolling back and forth through the image stack, each time exploring a different area on each image (low EMI and high number of courses). Scanners could be defined as scrolling progressively through the stack of images and focusing on different areas within each image slice (high EMI and low number of courses). Conclusions: Together, our results further enhance the understanding of how radiologists investigate three-dimensional volumes and may improve how to teach effective reading strategies to radiology residents.

Additional value of gadoxetic acid-enhanced MRI to conventional extracellular gadolinium-enhanced MRI for the surgical management of colorectal and neuroendocrine liver metastases

BACKGROUND

Liver resection being the only potentially curative treatment for patients with liver metastasis, it is critical to select the appropriate preoperative imaging modality. The aim of this study was to assess the impact of preoperative gadoxetic acid-enhanced MRI compared to a conventional extracellular gadolinium-enhanced MRI on the surgical management of colorectal and neuroendocrine liver metastasis.

METHODS

We included 110 patients who underwent both a gadoxetic acid-enhanced MRI (hepatospecific contrast) and conventional extracellular gadolinium for the evaluation of colorectal or neuroendocrine liver metastases, from January 2012 to December 2015 at the CHU de Québec - Université Laval. When the number of lesions differed, a hepatobiliary surgeon evaluated if the gadoxetic acid-enhanced MRI modified the surgical management.

RESULTS

Gadoxetic acid-enhanced MRI found new lesions in 25 patients (22.7%), excluded lesions in 18 patients (16.4%) and identified the same number in 67 patients (60.9%). The addition of the gadoxetic acid-enhanced MRI directly altered the surgical management in 19 patients overall (17.3% (95% CI [10.73-25.65])).

CONCLUSION

Despite the additional cost associated with gadoxetic acid-enhanced MRI compared to conventional extracellular gadolinium-enhanced MRI, the use of this contrast agent has a significant impact on the surgical management of patients with liver metastases.

Radio-Pathological Correlations in Patients with Liver Metastases for Colorectal Cancer

BACKGROUND

Colorectal cancer (CRC) is the most frequent gastrointestinal cancer. The liver is the organ most commonly affected by CRC metastases. Synchronous CRC liver metastases (CRCLM) are present in 15-25% at diagnosis, and metastases are confined to the liver in 70-80% of these cases. The aim of the present study was to investigate the existence of significant correlations between the pathological features and computed tomography scan morpho-densitometric findings.

SUMMARY

A retrospective study of prospectively collected data has been performed; all patients underwent curative-intent hepatic resection from January 2004 to December 2012 and had histologically confirmed CRCLM. Key Messages: Thirty-four (57%) patients were males; the mean age was 64.4 (±10.2) years. Statistically significant differences have been found with the percentages of intra-tumoral fibrosis (p = 0.038) and necrosis (p = 0.007); the values of fibrosis are higher in the absence of a peri-lesional ring, while those of necrosis are higher in the presence of a peri-lesional ring.There was a correlation between the histopathological response to treatments and the global attenuation levels observed in the computed tomography scan of CRCLM. Furthermore, the presence of a radiologically evidenced peripheral ring was associated with the amount of viable tumor cells in the periphery of the tumor, and with responses predominated by necrosis. More studies are needed to clarify the radiological and histological correlation and to be able to better select patients who are going to undergo surgery.

Evaluation of Contrast-Enhanced Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) in the Detection of Retropharyngeal Lymph Node Metastases in Nasopharyngeal Carcinoma Patients

INTRODUCTION

We performed this study to explore the diagnostic accuracies and cutoff values of contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI) for the detection and diagnosis of metastatic retropharyngeal lymph nodes (RLNs) in patients with nasopharyngeal carcinoma (NPC).

METHODS

One hundred and twenty-eight patients with a total of 159 RLNs were included in the study. The sizes of maximal and minimal axial diameters of each node on both contrast-enhanced CT and MRI images were measured. The characteristics of the RLNs (malignant or benign), as well as the survival of patients, were classified based on the results of follow-up MRI.

RESULTS

RLN size cutoffs of 4-11 mm for minimal axial diameter were used. We found that MRI showed higher sensitivity while CT demonstrated higher specificity. The reasonable criterion for the diagnosis of metastatic RLNs in MRI was a minimal axial diameter of ≥6 mm, which yielded a sensitivity, specificity and diagnostic odds ratio (DOR) of 0.71, 0.82 and 10.88.

CONCLUSION

The radiologic criteria that should be used for the assessment of RLN metastases in NPC patients are nodes with a minimal axial diameter of ≥6 mm on MR images.

Imaging of Colorectal Liver Metastases: New Developments and Pending Issues

Computed tomography (CT), magnetic resonance imaging (MRI), and 18-fluorideoxyglucose positron emission tomography (18FDG-PET) are historically the most accurate imaging techniques for diagnosing liver metastases. Recently, the combination of diffusion-weighted imaging and hepatospecific contrast media, such as gadoxetic acid in MRI, have been demonstrated to have the highest diagnostic accuracy, sensitivity, and specificity for detecting liver metastases. Various recent meta-analyses have confirmed the diagnostic superiority of this combination (diffusion-weighted imaging and gadoxetic acid-enhanced MRI), especially in terms of per lesion sensitivity, as compared with CT and 18FDG-PET, even for smaller lesions (≤1 cm). However, none of the oncological guidelines have suggested the use of MRI as a first-line technique for liver metastasis detection during the staging process of oncological patients. This review analyzes the history of the principal imaging techniques for the diagnosis of liver metastases, in particular of colorectal liver metastases, focusing on the most accurate method (diffusion-weighted imaging combined with gadoxetic acid-enhanced MRI), possible reasons for the lack of its diffusion in the guidelines, and possible future scenarios.

Enhancement pattern mapping technique for improving contrast-to-noise ratios and detectability of hepatobiliary tumors on multiphase computed tomography

PURPOSE

Currently, radiologists use tumor-to-normal tissue contrast across multiphase computed tomography (MPCT) for lesion detection. Here, we developed a novel voxel-based enhancement pattern mapping (EPM) technique and investigated its ability to improve contrast-to-noise ratios (CNRs) in a phantom study and in patients with hepatobiliary cancers.

METHODS

The EPM algorithm is based on the root mean square deviation between each voxel and a normal liver enhancement model using patient-specific (EPM-PA) or population data (EPM-PO). We created a phantom consisting of liver tissue and tumors with distinct enhancement signals under varying tumor sizes, motion, and noise. We also retrospectively evaluated 89 patients with hepatobiliary cancers who underwent active breath-hold MPCT between 2016 and 2017. MPCT phases were registered using a three-dimensional deformable image registration algorithm. For the patient study, CNRs of tumor to adjacent tissue across MPCT phases, EPM-PA and EPM-PO were measured and compared.

RESULTS

EPM resulted in statistically significant CNR improvement (P < 0.05) for tumor sizes down to 3 mm, but the CNR improvement was significantly affected by tumor motion and image noise. Eighty-two of 89 hepatobiliary cases showed CNR improvement with EPM (PA or PO) over grayscale MPCT, by an average factor of 1.4, 1.6, and 1.5 for cholangiocarcinoma, hepatocellular carcinoma, and colorectal liver metastasis, respectively (P < 0.05 for all).

CONCLUSIONS

EPM increases CNR compared with grayscale MPCT for primary and secondary hepatobiliary cancers. This new visualization method derived from MPCT datasets may have applications for early cancer detection, radiomic characterization, tumor treatment response, and segmentation.

IMPLICATIONS FOR PATIENT CARE

We developed a voxel-wise enhancement pattern mapping (EPM) technique to improve the contrast-to-noise ratio (CNR) of multiphase CT. The improvement in CNR was observed in datasets of patients with cholangiocarcinoma, hepatocellular carcinoma, and colorectal liver metastasis. EPM has the potential to be clinically useful for cancers with regard to early detection, radiomic characterization, response, and segmentation.