Radiologic measurements of tumor response to treatment: practical approaches and limitations

Precision of manual two-dimensional segmentations of lung and liver metastases and its impact on tumour response assessment using RECIST 1.1

Background

Response evaluation criteria in solid tumours (RECIST) has significant limitations in terms of variability and reproducibility, which may not be independent. The aim of the study was to evaluate the precision of manual bi-dimensional segmentation of lung, liver metastases, and to quantify the uncertainty in tumour response assessment.

Methods

A total of 520 segmentations of metastases from six livers and seven lungs were independently performed by ten physicians and ten scientists on CT images, reflecting the variability encountered in clinical practice. Operators manually contoured the tumours, firstly independently according to the RECIST and secondly on a preselected slice. Diameters and areas were extracted from the segmentations. Mean standard deviations were used to build regression models and 95% confidence intervals (95% CI) were calculated for each tumour size and for limits of progressive disease (PD) and partial response (PR) derived from RECIST 1.1.

Results

Thirteen aberrant segmentations (2.5%) were observed without significant differences between the physicians and scientists; only the mean area of liver tumours (p = 0.034) and mean diameter of lung tumours (p = 0.021) differed significantly. No difference was observed between the methods. Inter-observer agreement was excellent (intra-class correlation >0.90) for all variables. In liver, overlaps of the 95% CI with the 95% CI of limits of PD or PR were observed for diameters above 22.7 and 37.9 mm, respectively. An overlap of 95% CIs was systematically observed for area. No overlaps were observed in lung.

Conclusions

Although the experience of readers might not affect the precision of segmentation in lung and liver, the results of manual segmentation performed for tumour response assessment remain uncertain for large liver metastases.

Electronic supplementary material

The online version of this article (doi:10.1186/s41747-017-0015-4) contains supplementary material, which is available to authorized users.

Comparison of the RECIST and EORTC PET criteria in the tumor response assessment: a pooled analysis and review

PURPOSE

The EORTC PET criteria (EORTC criteria) are used to assess metabolic tumor response in patients with solid tumors. We conducted this pooled study to compare tumor responses according to the RECIST and EORTC criteria.

METHODS

Electronic databases were searched for eligible articles with the terms of "RECIST" or "EORTC criteria". We found seven articles with the data on the comparison of tumor responses by the RECIST and EORTC criteria.

RESULTS

A total of 181 patients were recruited from the seven studies. Ninety-two patients (50.8%) received cytotoxic chemotherapy and 89 were treated with targeted agents. The agreement of tumor responses between the RECIST and EORTC criteria was moderate (k = 0.493). Of 181 patients, 66 (36.5%) showed disagreement in the tumor responses: tumor response was upgraded in 54 patients and downgraded in 12 when adopting the EORTC criteria. The estimated overall response rates were significantly different between the two criteria (52.5% by the EORTC vs. 29.8% by the RECIST, P < 0.0001). When comparing the two criteria according to the anti-cancer treatments (chemotherapy or targeted therapy), the levels of agreement in tumor responses were not excellent (k = 0.461 for chemotherapy and k = 0.524 for targeted therapy, respectively) regardless of therapeutic types.

CONCLUSION

This pooled study indicates that the concordance of tumor responses between the RECIST and EORTC criteria is not excellent. When adopting the EORTC criteria instead of the RECIST, the overall response rate was significantly increased.

Evaluation of inter-observer variability according to RECIST 1.1 and its influence on response classification in CT measurement of liver metastases

OBJECTIVE

The aim of this study is the evaluation of inter-observer variability in the measurement of liver metastases according to RECIST and its influence on response classification.

PATIENTS AND METHODS

A total of 100 radiologists measured liver target lesions, on pre- and post-chemotherapy CT scans of three patients. Each observer filled out a questionnaire about his personal and work features. The evaluations of a well experienced radiologist, considered as "the gold standard", were compared to those taken by the observers. The percentage of the observers in agreement with the reviewer, in terms of the response category and in terms of inter-observer variability, was calculated for each patient.

RESULTS

The percentage of the inter-observer agreement was elevated. Most of the observers in agreement with the reviewer were senior radiologists, while those who disagreed were junior radiologist, but this result did not reach a statistical significance. More than 30% of observers disagreed with the reviewer at least in one of the three cases.

CONCLUSIONS

RECIST measurements are reproducible on a large and heterogeneous population of radiologists. Age and expertise of the radiologist remain the most critical factors: this suggests a revision by well-experienced radiologists in clinical trials.

An integrated segmentation and shape-based classification scheme for distinguishing adenocarcinomas from granulomas on lung CT

PURPOSE

Distinguishing between benign granulmoas and adenocarcinomas is confounded by their similar visual appearance on routine CT scans. Unfortunately, owing to the inability to discriminate these lesions radigraphically, many patients with benign granulomas are subjected to unnecessary surgical wedge resections and biopsies for pathologic confirmation of cancer presence or absence. This suggests the need for improved computerized characterization of these nodules in order to distinguish between these two classes of lesions on CT scans. While there has been substantial interest in the use of textural analysis for radiomic characterization of lung nodules, relatively less work has been done in shape based characterization of lung nodules, particularly with respect to granulmoas and adenocarcinomas. The primary goal of this study is to evaluate the role of 3D shape features for discrimination of benign granulomas from malignant adenocarcinomas on lung CT images. Towards this end we present an integrated framework for segmentation, feature characterization and classification of these nodules on CT.

METHODS

The nodule segmentation method starts with separation of lung regions from the surrounding lung anatomy. Next, the lung CT scans are projected into and represented in a three dimensional spectral embedding (SE) space, allowing for better determination of the boundaries of the nodule. This then enables the application of a gradient vector flow active contour (SEGvAC) model for nodule boundary extraction. A set of 24 shape features from both 2D slices and 3D surface of the segmented nodules are extracted, including features pertaining to the angularity, spiculation, elongation and nodule compactness. A feature selection scheme, PCA-VIP, is employed to identify the most discriminating set of features to distinguish granulmoas from adenocarcinomas within a learning set of 82 patients. The features thus identified were then combined with a support vector machine classifier and independently validated on a distinct test set comprising 67 patients. The performance of the classifier for both of the training and validation cohorts was evaluated by the area under receiver characteristic curve (ROC).

RESULTS

We used 82 and 67 studies from two different institutions respectively for training and independent validation of the model and the shape features. The Dice coefficient between automatically segmented nodules by SEGvAC and the manual delineations by expert radiologists (readers) was 0.84± 0.04 whereas inter-reader segmentation agreement was 0.79± 0.12. We also identified a set of consistent features (Roughness, Convexity and Spherecity) that were found to be strongly correlated across both manual and automated nodule segmentations (R > 0.80, p < 0.0001) and capture the marginal smoothness and 3D compactness of the nodules. On the independent validation set of 67 studies our classifier yielded a ROC AUC of 0.72 and 0.64 for manually- and automatically segmented nodules respectively. On a subset of 20 studies, the AUCs for the two expert radiologists and 1 pulmonologist were found to be 0.82, 0.68 and 0.58 respectively.

CONCLUSIONS

The major finding of this study was that certain shape features appear to differentially express between granulomas and adenocarcinomas and thus computer extracted shape cues could be used to distinguish these radiographically similar pathologies.

Neoadjuvant Ifosfamide and Epirubicin in the Treatment of Malignant Peripheral Nerve Sheath Tumors

Background and Objectives. Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive soft tissue sarcomas with poor overall survival. Response to chemotherapy has been debated for these tumors. Methods. We performed a retrospective analysis of the patients at our institution with a biopsy-proven diagnosis of MPNST that underwent neoadjuvant chemotherapy prior to surgery. Results. We retrospectively identified five patients who received neoadjuvant chemotherapy with epirubicin and ifosfamide that demonstrated a 30% reduction in tumor growth and a 60% response rate by RECIST criteria. Additionally, a metabolic response was observed in all three patients who received serial PET scans during neoadjuvant treatment. The clinical benefit rate, which includes stable disease, was 100%. Conclusions. Our data suggest that MPNSTs do respond to epirubicin and ifosfamide based chemotherapy and prospective studies are warranted to further define the clinical benefit.

Statistical tools for the temporal analysis and classification of lung lesions

BACKGROUND AND OBJECTIVE

Lung cancer remains one of the most common cancers globally. Temporal evaluation is an important tool for analyzing the malignant behavior of lesions during treatment, or of indeterminate lesions that may be benign. This work proposes a methodology for the analysis, quantification, and visualization of small (local) and large (global) changes in lung lesions. In addition, we extract textural features for the classification of lesions as benign or malignant.

METHODS

We employ the statistical concept of uncertainty to associate each voxel of a lesion to a probability that changes occur in the lesion over time. We employ the Jensen divergence and hypothesis test locally to verify voxel-to-voxel changes, and globally to capture changes in lesion volumes.

RESULTS

For the local hypothesis test, we determine that the change in density varies by between 3.84 and 40.01% of the lesion volume in a public database of malignant lesions under treatment, and by between 5.76 and 35.43% in a private database of benign lung nodules. From the texture analysis of regions in which the density changes occur, we are able to discriminate lung lesions with an accuracy of 98.41%, which shows that these changes can indicate the true nature of the lesion.

CONCLUSION

In addition to the visual aspects of the density changes occurring in the lesions over time, we quantify these changes and analyze the entire set using volumetry. In the case of malignant lesions, large b-divergence values are associated with major changes in lesion volume. In addition, this occurs when the change in volume is small but is associated with significant changes in density, as indicated by the histogram divergence. For benign lesions, the methodology shows that even in cases where the change in volume is small, a change of density occurs. This proves that even in lesions that appear stable, a change in density occurs.

Tumor burden monitoring using cell-free tumor DNA could be limited by tumor heterogeneity in advanced breast cancer and should be evaluated together with radiographic imaging

Background

Accurate measurement of tumor burden in breast cancer disease is essential to improve the clinical management of patients. In this study, we evaluate whether the fluctuations in the fraction of PIK3CA mutant allele correlates with tumor response according to RECIST criteria and tumor markers quantification.

Methods

Eighty six plasma samples were analyzed by digital PCR using Rare Mutation Assays for E542K, E545K and H1047R. Mutant cfDNA and tumor markers CA15-3 and CEA were compared with radiographic imaging.

Results

The agreement between PIK3CA mutation status in FFPE samples and circulating tumor DNA (ctDNA) was moderate (K = 0.591; 95% IC = 0.371–0.811). Restricting the analysis to the metastatic patients, we found a good agreement between PIK3CA mutation status assessed in liquid and solid biopsy (K = 0.798 95%; IC = 0.586–1). ctDNA showed serial changes with fluctuations correlating with tumor markers 15.3 and CEA in 7 out of 8 cases with Pearson correlation coefficients ranging from 0.99 to 0.46 and from 0.99 to 0.38 respectively. Similarly, fluctuations in the fraction of PIK3CA mutant allele always correlated with changes in lesion size seen on images, although in two cases it did not correlate with treatment responses as defined by RECIST criteria.

Conclusion

oncogenic mutation quantification in plasma samples can be useful to monitor treatment outcome. However, it might be limited by tumor heterogeneity in advanced disease and it should be evaluated together with radiographic imaging.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3185-9) contains supplementary material, which is available to authorized users.

Algorithm Variability in the Estimation of Lung Nodule Volume From Phantom CT Scans: Results of the QIBA 3A Public Challenge

RATIONALE AND OBJECTIVES

Quantifying changes in lung tumor volume is important for diagnosis, therapy planning, and evaluation of response to therapy. The aim of this study was to assess the performance of multiple algorithms on a reference data set. The study was organized by the Quantitative Imaging Biomarker Alliance (QIBA).

MATERIALS AND METHODS

The study was organized as a public challenge. Computed tomography scans of synthetic lung tumors in an anthropomorphic phantom were acquired by the Food and Drug Administration. Tumors varied in size, shape, and radiodensity. Participants applied their own semi-automated volume estimation algorithms that either did not allow or allowed post-segmentation correction (type 1 or 2, respectively). Statistical analysis of accuracy (percent bias) and precision (repeatability and reproducibility) was conducted across algorithms, as well as across nodule characteristics, slice thickness, and algorithm type.

RESULTS

Eighty-four percent of volume measurements of QIBA-compliant tumors were within 15% of the true volume, ranging from 66% to 93% across algorithms, compared to 61% of volume measurements for all tumors (ranging from 37% to 84%). Algorithm type did not affect bias substantially; however, it was an important factor in measurement precision. Algorithm precision was notably better as tumor size increased, worse for irregularly shaped tumors, and on the average better for type 1 algorithms. Over all nodules meeting the QIBA Profile, precision, as measured by the repeatability coefficient, was 9.0% compared to 18.4% overall.

CONCLUSION

The results achieved in this study, using a heterogeneous set of measurement algorithms, support QIBA quantitative performance claims in terms of volume measurement repeatability for nodules meeting the QIBA Profile criteria.

Feasibility of assessing pulmonary blood volume using C-arm CT during transpulmonary chemoperfusion and chemoembolization in primary and secondary lung tumours

OBJECTIVE

Assessment of parenchymal blood volume (PBV) of primary and secondary pulmonary malignancies by using a C-arm CT, regarding its role in detecting early functional response to transpulmonary chemoembolization (TPCE) and clinical practicability.

METHODS

21 patients with a mean age of 56.77 years, who were assigned to TPCE during their palliative treatment, were included. PBV and the diameter of tumours were analyzed. PBV maps were calculated from three-dimensional CT-angiographic (3D-CTA) data sets. Imaging was performed on a flat detector, C-arm CT. Groups of response were classified according to the criteria of the response evaluation criteria in solid tumours. Statistically significant differences were determined and Pearson's regression analysis correlated PBV and diameter as parameters of response to treatment.

RESULTS

During 4.91 sessions, median diameter increased 18.18% (p > 0.05) and PBV reduced 39.62% (p > 0.05). Functional and imaging response per tumour was statistical significantly different (p ≤ 0.05). Correlation coefficient was r = 0.058. 2/41 tumours showed partial response; 31/41 tumours showed stable disease; and 8/41 tumours showed progressive disease. The highest pre-treatment PBV values were measured in decreasing tumours (206.93 ml l(-1)), and the lowest values were measured in increasing tumours (60.17 ml l(-1); p > 0.05). The lowest values were also measured in lung cancer (53.02 ml l(-1)) that was significantly different to uterine leiomyosarcoma (103.31 ml l(-1)) and renal cell cancer (113.14 ml l(-1); p ≤ 0.05).

CONCLUSION

Assessment of PBV maps by using 3D-CTA image data is feasible in the clinical routine. PBV shows a stronger response to TPCE treatment than measurement in diameter and should be considered as a response parameter for early detection.

ADVANCES IN KNOWLEDGE

Assessment of PBV using C-arm CT during TPCE is a feasible technique. Assessment of PBV might be useful in assessing response to treatment.

Irreversible Electroporation (IRE): Standardization of Terminology and Reporting Criteria for Analysis and Comparison

BACKGROUND

Irreversible electroporation (IRE) as newer ablation modality has been introduced and its clinical niche is under investigation. At present just one IRE system has been approved for clinical use and is currently commercially available (NanoKnife® system). In 2014, the International Working Group on Image-Guided Tumor Ablation updated the recommendation about standardization of terms and reporting criteria for image-guided tumor ablation. The IRE method is not covered in detail. But the non-thermal IRE method and the NanoKnife System differ fundamentally from established ablations techniques, especially thermal approaches, e.g. radio frequency ablation (RFA).

MATERIAL/METHODS

As numerous publications on IRE with varying terminology exist so far - with numbers continuously increasing - standardized terms and reporting criteria of IRE are needed urgently. The use of standardized terminology may then allow for a better inter-study comparison of the methodology applied as well as results achieved.

RESULTS

Thus, the main objective of this document is to supplement the updated recommendation for image-guided tumor ablation by outlining a standardized set of terminology for the IRE procedure with the NanoKnife Sytem as well as address essential clinical and technical informations that should be provided when reporting on IRE tumor ablation.

CONCLUSIONS

We emphasize that the usage of all above recommended reporting criteria and terms can make IRE ablation reports comparable and provide treatment transparency to assess the current value of IRE and provide further development.

CT Appearance of Hepatocellular Carcinoma after Locoregional Treatments: A Comprehensive Review

Hepatocellular carcinoma (HCC) is a major health problem worldwide, affecting more than 600,000 new patients per year. Curative treatments are available in a small percentage of patients, while most of them present in stages requiring locoregional treatments such as thermoablation, transarterial chemoembolization, and/or radioembolization. These therapies result in specific imaging features that the general radiologist has to be aware of in order to assess the response to treatment and to correctly manage the follow-up of treated patients. Multiphasic helical computed tomography has become a popular imaging modality for detecting hypervascular tumors and characterizing liver lesions. On this basis, many staging and diagnostic systems have been proposed for evaluating response to all different existing strategies. Radiofrequencies and microwaves generate thermoablation of tumors, and transarterial chemoembolization exploits the double effect of the locoregional administration of drugs and embolizing particles. Eventually radioembolization uses a beta-emitting isotope to induce necrosis. Therefore, the aim of this comprehensive review is to analyze and compare CT imaging appearance of HCC after various locoregional treatments, with regard to specific indications for all possible procedures.

Comparison of metabolic and anatomic response to chemotherapy based on PERCIST and RECIST in patients with advanced stage non-small cell lung cancer

BACKGROUND

The aim of this study was to explore the prognostic role of metabolic response to chemotherapy, determined by FDG-PET, in patients with metastatic non-small-cell lung cancer (NSCLC).

MATERIALS AND METHODS

Thirty patients with metastatic NSCLC were analyzed for prognostic factors related to overall survival (OS) and progression free survival (PFS). Disease evaluation was conducted with FDG-PET/CT and contrast-enhanced CT prior to and at the end of first-line chemotherapy. Response evaluation of 19 of 30 patients was also performed after 2-3 cycles of chemotherapy. Morphological and metabolic responses were assessed according to RECIST and PERCIST, respectively.

RESULTS

The median OS and PFS were 11 months and 6.2 months, respectively. At the end of first-line chemotherapy, 10 patients achieved metabolic and anatomic responses. Of the 19 patients who had an interim response analysis after 2-3 cycles of chemotherapy, 3 achieved an anatomic response, while 9 achieved a metabolic response. In univariate analyses, favorable prognostic factors for OS were number of cycles of first-line chemotherapy, and achieving a response to chemotherapy at completion of therapy according to the PERCIST and RECIST. The OS of patients with a metabolic response after 2-3 cycles of chemotherapy was also significantly extended. Anatomic response at interim analysis did not predict OS, probably due to few patients with anatomic response. In multivariate analyses, metabolic response after completion of therapy was an independent prognostic factor for OS.

CONCLUSIONS

Metabolic response is at least as effective as anatomic response in predicting survival. Metabolic response may be an earlier predictive factor for treatment response and OS in NSCLC patients.

Erlotinib versus carboplatin and paclitaxel in advanced lepidic adenocarcinoma: IFCT-0504

The IFCT-0504 phase II trial evaluated the efficacy of erlotinib versus carboplatin-paclitaxel (CP) as first-line treatment in 130 cases of advanced lepidic-predominant adenocarcinoma (ADC).The primary objective of the study was treatment efficacy, evaluated based on an end-point of disease control at 16 weeks.The primary objective was met, with a disease control in 35 (53%) out of 66 patients treated with CP and in 25 (39.1%) out of 64 patients treated with erlotinib. Median progression-free survival (PFS) for the total population was 3.6 months. The disease control rate did not differ between either the therapeutic arms or pathological subtypes, whereas there was a strong interaction between treatment arms and tumour pathological subtypes for PFS (p=0.009). Mucinous tumour patients treated with erlotinib exhibited an increased progression risk (hazard ratio 3.4, 95% CI 1.7-6.5; p≤0.001). The PFS for nonmucinous tumour patients was similar in both arms. Median overall survival was 20.1 months and did not differ between therapeutic arms. These findings were not further elucidated by molecular analyses and the toxicity profiles were as expected.Our study demonstrated the dominant role of CP alongside erlotinib in the management of advanced lepidic ADC. Based on these findings, erlotinib should not be administered in first-line therapy to patients with lepidic ADC in the absence of an epidermal growth factor receptor mutation.

Sustained systemic response paralleled with ovarian metastasis progression by sunitinib in metastatic renal cell carcinoma: Is this an anti-angiogenic potentiation of cancer?

Metastatic renal cell cancer is associated with poor prognosis and survival and is resistant to conventional chemotherapy. Therapeutic targeting of molecular pathways for tumor angiogenesis and other specific activation mechanisms offers improved tumor response and prolonged survival. A 48-year-old, female patient presented with large right renal mass with features suggesting of renal cell cancer without metastasis on contrast enhanced computed tomography (CT). Right radical nephrectomy was done. After 9 months of surgery, she got metastasis in lung, liver and ovary. The patient received sunitinib via an expanded access program. After eight 6-week cycles of sunitinib, a reassessment CT scan confirmed an excellent partial response with the almost complete disappearance (90%) of liver and lung metastasis but the adnexal mass had increased in size (>10 times) and the possibility was thought of second malignancy. Excision of the mass performed. Histopathology of the mass depicted metastatic renal cell cancer. There is possibility of a ‘site-specific anti-angiogenic potentiation mechanism’ of malignancy in relation to sunitinib based upon the preclinical studies, in reference to the index case. Regression of one site with concurrent progression is possible. The exact mechanism of site-specific response, especially organ specific progression by vascular endothelial growth factor inhibitors in metastatic renal cell cancer warrants further study.

Test-retest reproducibility analysis of lung CT image features

Quantitative size, shape, and texture features derived from computed tomographic (CT) images may be useful as predictive, prognostic, or response biomarkers in non-small cell lung cancer (NSCLC). However, to be useful, such features must be reproducible, non-redundant, and have a large dynamic range. We developed a set of quantitative three-dimensional (3D) features to describe segmented tumors and evaluated their reproducibility to select features with high potential to have prognostic utility. Thirty-two patients with NSCLC were subjected to unenhanced thoracic CT scans acquired within 15 min of each other under an approved protocol. Primary lung cancer lesions were segmented using semi-automatic 3D region growing algorithms. Following segmentation, 219 quantitative 3D features were extracted from each lesion, corresponding to size, shape, and texture, including features in transformed spaces (laws, wavelets). The most informative features were selected using the concordance correlation coefficient across test-retest, the biological range and a feature independence measure. There were 66 (30.14%) features with concordance correlation coefficient ≥ 0.90 across test-retest and acceptable dynamic range. Of these, 42 features were non-redundant after grouping features with R (2) Bet ≥ 0.95. These reproducible features were found to be predictive of radiological prognosis. The area under the curve (AUC) was 91% for a size-based feature and 92% for the texture features (runlength, laws). We tested the ability of image features to predict a radiological prognostic score on an independent NSCLC (39 adenocarcinoma) samples, the AUC for texture features (runlength emphasis, energy) was 0.84 while the conventional size-based features (volume, longest diameter) was 0.80. Test-retest and correlation analyses have identified non-redundant CT image features with both high intra-patient reproducibility and inter-patient biological range. Thus making the case that quantitative image features are informative and prognostic biomarkers for NSCLC.

Proposal of a hybrid approach for tumor progression and tumor-induced angiogenesis

One of the main challenges in cancer modelling is to improve the knowledge of tumor progression in areas related to tumor growth, tumor-induced angiogenesis and targeted therapies efficacy. For this purpose, incorporate the expertise from applied mathematicians, biologists and physicians is highly desirable. Despite the existence of a very wide range of models, involving many stages in cancer progression, few models have been proposed to take into account all relevant processes in tumor progression, in particular the effect of systemic treatments and angiogenesis. Composite biological experiments, both in vitro and in vivo, in addition with mathematical modelling can provide a better understanding of theses aspects. In this work we proposed that a rational experimental design associated with mathematical modelling could provide new insights into cancer progression. To accomplish this task, we reviewed mathematical models and cancer biology literature, describing in detail the basic principles of mathematical modelling. We also analyze how experimental data regarding tumor cells proliferation and angiogenesis in vitro may fit with mathematical modelling in order to reconstruct in vivo tumor evolution. Additionally, we explained the mathematical methodology in a comprehensible way in order to facilitate its future use by the scientific community.

Assessing response to treatment of bone metastases from breast cancer: what should be the standard of care?

Bone is the most common site for breast cancer metastases, occurring in up to 70% of those with metastatic disease. In order to effectively manage these patients, it is essential to have consistent, reproducible and validated methods of assessing response to therapy. We present current clinical practice of imaging response assessment of bone metastases. We also review the biology of bone metastases and measures of response assessment including clinical assessment, tumour markers and imaging techniques; bone scans (BSs), computed tomography (CT), positron emission tomography, magnetic resonance imaging (MRI) and whole-body diffusion-weighted MRI (WB DW-MRI). The current standard of care of BSs and CT has significant limitations and are not routinely recommended for the purpose of response assessment in the bones. WB DW-MRI has the potential to address this unmet need and should be evaluated in clinical trials.

Pitfalls in RECIST Data Extraction for Clinical Trials: Beyond the Basics

Response Evaluation Criteria in Solid Tumors (RECIST) is a standardized methodology for determining therapeutic response to anticancer therapy using changes in lesion appearance on imaging studies. Many radiologists are now using RECIST in their routine clinical workflow, as part of consultative arrangements, or within dedicated imaging core laboratories. Although basic RECIST methodology is well described in published articles and online resources, inexperienced readers may encounter difficulties with certain nuances and subtleties of RECIST. This article illustrates a set of pitfalls in RECIST assessment considered to be "beyond the basics." These pitfalls were uncovered during a quality improvement review of a recently established cancer imaging core laboratory staffed by radiologists with limited prior RECIST experience. Pitfalls are presented in four categories: (1) baseline selection of lesions, (2) reassessment of target lesions, (3) reassessment of nontarget lesions, and (4) identification of new lesions. Educational and operational strategies for addressing these pitfalls are suggested. Attention to these pitfalls and strategies may improve the overall quality of RECIST assessments performed by radiologists.

Magnetic resonance imaging of the liver after loco-regional and systemic therapy

Assessment of tumor response is crucial in determining the effectiveness of loco-regional and systemic therapy, and for determining the need for subsequent treatment. The ultimate goal is to improve patient's survival. Changes in tumor size and enhancement after therapy may not be detected early by the traditional response criteria. Tumor response is better assessed in the entire tumor volume rather than in a single axial plane. The purpose of this article is to familiarize the reader with early treatment response assessed by anatomic and volumetric functional magnetic resonance imaging metrics of the liver after loco-regional and systemic therapy.

Comparison of RECIST 1.0 and RECIST 1.1 in Patients with Metastatic Cancer: A Pooled Analysis

BACKGROUND

We conducted this pooled analysis to investigate the impact of RECIST 1.1 on the selection of target lesions and classification of tumor response, in comparison with RECIST 1.0. Methods : We searched MEDLINE and EMBASE for articles with terms of RECIST 1.0 or RECIST 1.1. We looked into all abstracts and virtual meeting presentations from the conferences of ASCO and ESMO between 2009 and 2013.

RESULTS

There were six articles in the literature comparing the clinical impacts of RECIST 1.0 and RECIST 1.1 in patients with metastatic cancer. A total of 359 patients were recruited from the six trials; 217 with non-small cell lung cancer, 61 with gastric cancer, 58 with colorectal cancer, and 23 with thyroid cancer. The number of target lesions by RECIST 1.1 was significantly lower than that by RECIST 1.0 (P<0.001). Because of new lymph node criteria, fourteen patients (3.1%) had no target lesions when adopting RECIST 1.1. RECIST 1.1 showed high concordance with RECIST 1.0 in the assessment of tumor responses (k = 0.903). Sixteen patients (4.8%) showed disagreement between the two criteria.

CONCLUSION

This pooled study demonstrated that RECIST 1.1 showed a highly concordant response assessment with RECIST 1.0 in patients with metastatic cancer.

CT perfusion as an imaging biomarker in monitoring response to neoadjuvant bevacizumab and radiation in soft-tissue sarcomas: comparison with tumor morphology, circulating and tumor biomarkers, and gene expression

OBJECTIVE

The purpose of this study was to evaluate the role of CT perfusion in monitoring response to neoadjuvant antiangiogenic and radiation therapy in resectable soft-tissue sarcomas and correlate the findings with tumor size, circulating and tumor biomarkers, and gene expression.

SUBJECTS AND METHODS

This phase II clinical trial included 20 patients (13 men and 7 women; mean age, 55 years) with soft-tissue sarcomas who were undergoing treatment with the antiangiogenic drug bevacizumab followed by bevacizumab, radiation, and surgical resection. The patients underwent CT perfusion and diagnostic contrast-enhanced CT at baseline, at 2 weeks after bevacizumab therapy, and after completion of bevacizumab and radiation therapy. Multiple CT perfusion parameters (blood flow, blood volume, mean transit time, and permeability) were correlated with tumor size, circulating and tumor biomarkers, and gene expression.

RESULTS

Two weeks after bevacizumab therapy, there was substantial fall in blood volume (31.9% reduction, p = 0.01) with more pronounced reduction in blood flow, blood volume, and permeability after treatment completion (53-64% reduction in blood flow, blood volume, and permeability; p = 0.001), whereas tumor size showed no significant change (p = 0.34). Tumors with higher baseline blood volume and lower baseline tumor size showed superior response to bevacizumab and radiation (p = 0.05). There was also an increase in median plasma vascular endothelial growth factor and placental-derived growth factor concentration after bevacizumab therapy paralleled by a decrease in tumor perfusion depicted by CT perfusion, although this was not statistically significant (p = 0.4). The baseline tumor microvessel density (MVD) correlated with blood flow (p = 0.04). At least 20 different genes were differentially expressed in tumors with higher and lower baseline perfusion.

CONCLUSION

CT perfusion is more sensitive than tumor size for monitoring early and late response to bevacizumab and radiation therapy. CT perfusion parameters correlate with MVD, and the gene expression levels of baseline tumors could potentially predict treatment response.

Volume-based response evaluation with consensual lesion selection: a pilot study by using cloud solutions and comparison to RECIST 1.1

RATIONALE AND OBJECTIVES

Lesion volume is considered as a promising alternative to Response Evaluation Criteria in Solid Tumors (RECIST) to make tumor measurements more accurate and consistent, which would enable an earlier detection of temporal changes. In this article, we report the results of a pilot study aiming at evaluating the effects of a consensual lesion selection on volume-based response (VBR) assessments.

MATERIALS AND METHODS

Eleven patients with lung computed tomography scans acquired at three time points were selected from Reference Image Database to Evaluate Response to therapy in lung cancer (RIDER) and proprietary databases. Images were analyzed according to RECIST 1.1 and VBR criteria by three readers working in different geographic locations. Cloud solutions were used to connect readers and carry out a consensus process on the selection of lesions used for computing response. Because there are not currently accepted thresholds for computing VBR, we have applied a set of thresholds based on measurement variability (-35% and +55%). The benefit of this consensus was measured in terms of multiobserver agreement by using Fleiss kappa (κfleiss) and corresponding standard errors (SE).

RESULTS

VBR after consensual selection of target lesions allowed to obtain κfleiss = 0.85 (SE = 0.091), which increases up to 0.95 (SE = 0.092), if an extra consensus on new lesions is added. As a reference, the agreement when applying RECIST without consensus was κfleiss = 0.72 (SE = 0.088). These differences were found to be statistically significant according to a z-test.

CONCLUSIONS

An agreement on the selection of lesions allows reducing the inter-reader variability when computing VBR. Cloud solutions showed to be an interesting and feasible strategy for standardizing response evaluations, reducing variability, and increasing consistency of results in multicenter clinical trials.

Factors affecting the restaging accuracy of magnetic resonance imaging after preoperative chemoradiation in patients with rectal cancer

PURPOSES

We evaluated patient or tumor factors associated with the preoperative restaging accuracy of magnetic resonance imaging (MRI) for determining T and N stages as well as circumferential resection margin (CRM) involvement after chemoradiation (CRT) in patients with locally advanced rectal cancer.

METHODS

Seventy-seven patients with rectal cancer that were treated with preoperative CRT (50.4 Gy) followed by radical resection were included. Post-CRT MRI was performed approximately 4 weeks after preoperative CRT.

RESULTS

The median tumor distance from the anal verge was 6 cm, 48 (62%) of which were anterior and 29 (38%) posterior. The median tumor diameter was 3 cm. A stage-by-stage comparison showed that correct staging occurred in 62%, 43%, and 86% of patients for T staging, N staging, and CRM prediction, respectively. Shorter distance to the anal verge (<5 cm), smaller tumor diameter (<1 cm), and anterior tumor location were associated with incorrect T staging. There were no significant variables in terms of N staging accuracy. Shorter tumor distance and anterior tumor location were associated with incorrect CRM prediction.

CONCLUSIONS

Our findings suggest that specific tumor factors such as small, distal, or anterior rectal tumors are closely associated with the accuracy of MRI after preoperative CRT.

Y90 radioembolization of colorectal cancer liver metastases: response assessment by contrast-enhanced computed tomography with or without PET-CT guidance

PURPOSE

To compare various computed tomography (CT) parameters to the positron emission tomography with computed tomography (PET-CT) response, with or without PET guidance for the response assessment of colorectal cancer (CRC) metastases treated by Y90 radioembolization.

METHODS

Thirty-six CRC metastases were retrospectively evaluated on 18F-Fluoro-Deoxy-Glucose PET-CT and contrast-enhanced computed tomography (CECT) performed at baseline and 2-3 months after Y90 radioembolization.

RESULTS

Median SUVmax values decreased from 11.39 to 6.71 after radioembolization (P<.001), and 23/36 (64%) metastases were categorized metabolic responses according to European Organisation for Research and Treatment of Cancer criteria. Only a decrease of the mean attenuation in the structural (P<.001) and metabolic active volume (P<.001) was observed. The change in these criteria was correlated with the change of SUVmax.

Imaging tumor response following liver-directed intra-arterial therapy

Liver-directed intra-arterial therapies are palliative treatment options for patients with unresectable liver cancer; their use has also resulted in patients being downstaged leading to curative resection and transplantation. These intra-arterial therapies include transarterial embolization, conventional transarterial chemoembolization (TACE), drug-eluting bead TACE and radioembolization. Assessment of imaging response following these liver-directed intra-arterial therapies is challenging but pivotal for patient management. Size measurements based on computed tomography or magnetic resonance imaging (MRI) have been traditionally used to assess tumor response to therapy. However, these anatomic changes lag behind functional changes and may require months to occur. Further, these intra-arterial therapies cause acute tumor necrosis, which may result in a paradoxical increase in tumor size on early follow-up imaging despite complete cell death or necrosis. This concept is unique comparing to changes seen following systemic chemotherapy. The recent development of functional imaging techniques including diffusion-weighted MRI (DW MRI) and positron emission tomography (PET) allow for early assessment of treatment response and even prediction of overall tumor response to intra-arterial therapies. Although the results of DW MRI and PET studies are promising, the impact of these imaging modalities to assess treatment response has been limited without standardized protocols. The aim of this review article is to delineate the best practice for assessing tumor response in patients with primary or secondary hepatic malignancies undergoing intra-arterial therapies.

CT versus FDG-PET/CT response evaluation in patients with metastatic colorectal cancer treated with irinotecan and cetuximab

We compared morphologic computed tomography (CT)-based to metabolic fluoro-deoxy-glucose (FDG) positron emission tomography (PET)/CT-based response evaluation in patients with metastatic colorectal cancer and correlated the findings with survival and KRAS status. From 2006 to 2009, patients were included in a phase II trial and treated with cetuximab and irinotecan every second week. They underwent FDG-PET/CT examination at baseline and after every fourth treatment cycle. Response evaluation was performed prospectively according to Response Evaluation Criteria in Solid Tumors (RECIST 1.0) and retrospectively according to Positron Emission Tomography Response Criteria in Solid Tumors (PERCIST). Best overall responses were registered. Sixty-one patients were eligible for response evaluation. Partial response (PR) rate was 18%, stable disease (SD) rate 64%, and progressive disease (PD) rate 18%. Partial metabolic response (PMR) rate was 56%, stable metabolic disease rate 33%, and progressive metabolic disease (PMD) rate 11%. Response agreement was poor, κ-coefficient 0.19. Hazard ratio for overall survival for responders (PR/PMR) versus nonresponders (PD/PMD) was higher for CT- than for FDG-PET/CT evaluation. Within patients with KRAS mutations, none had PR but 44% had PMR. In conclusion, morphologic and metabolic response agreement was poor primarily because a large part of the patients shifted from SD with CT evaluation to PMR when evaluated with FDG-PET/CT. Furthermore, a larger fraction of the patients with KRAS mutations had a metabolic treatment response.

Current status of imaging and emerging techniques to evaluate liver metastases from colorectal carcinoma

Colorectal cancer is the third most common cancer diagnosed in both men and women in the United States. Liver is a common site of tumor spread and in approximately 30% of the cases; synchronous liver disease is present at the time of diagnosis. Early detection of liver metastases is crucial to appropriately select patients who may benefit from hepatic resection among those needing chemotherapy, to improve 5-year survival. Advances in imaging techniques have contributed greatly to the management of these patients. Multidetector computed tomography is the most useful test for initial staging and in posttreatment surveillance settings. Magnetic resonance imaging is considered superior to multidetector computed tomography and positron emission tomography for the detection and characterization of small lesions and for liver evaluation in the presence of background fatty liver changes. Positron emission tomography-computed tomography has a problem-solving role in the detection of distant metastasis and in posttreatment evaluation. The advanced imaging methods also serve a role in selecting appropriate patients for radiologically targeted therapies and in monitoring response to conventional and novel therapies.

Multimodal imaging evaluation in staging of rectal cancer

Rectal cancer is a common cancer and a major cause of mortality in Western countries. Accurate staging is essential for determining the optimal treatment strategies and planning appropriate surgical procedures to control rectal cancer. Endorectal ultrasonography (EUS) is suitable for assessing the extent of tumor invasion, particularly in early-stage or superficial rectal cancer cases. In advanced cases with distant metastases, computed tomography (CT) is the primary approach used to evaluate the disease. Magnetic resonance imaging (MRI) is often used to assess preoperative staging and the circumferential resection margin involvement, which assists in evaluating a patient’s risk of recurrence and their optimal therapeutic strategy. Positron emission tomography (PET)-CT may be useful in detecting occult synchronous tumors or metastases at the time of initial presentation. Restaging after neoadjuvant chemoradiotherapy (CRT) remains a challenge with all modalities because it is difficult to reliably differentiate between the tumor mass and other radiation-induced changes in the images. EUS does not appear to have a useful role in post-therapeutic response assessments. Although CT is most commonly used to evaluate treatment responses, its utility for identifying and following-up metastatic lesions is limited. Preoperative high-resolution MRI in combination with diffusion-weighted imaging, and/or PET-CT could provide valuable prognostic information for rectal cancer patients with locally advanced disease receiving preoperative CRT. Based on these results, we conclude that a combination of multimodal imaging methods should be used to precisely assess the restaging of rectal cancer following CRT.

Spectrum of multilocular cystic hepatic lesions: CT and MR imaging findings with pathologic correlation

A multilocular cystic hepatic lesion detected at computed tomography (CT) and magnetic resonance (MR) imaging is a common but nonspecific radiologic finding that can cause potential challenges for differential diagnosis. This imaging pattern may be observed in a wide spectrum of common and uncommon neoplastic or nonneoplastic entities. Neoplastic lesions include cystadenoma, cystadenocarcinoma, hepatocellular carcinoma (HCC), metastases, mesenchymal hamartoma, and inflammatory myofibroblastic tumor. Nonneoplastic lesions include hepatic abscess, echinococcal cyst, intrahepatic hematoma, and biloma. The multiple coalescent cysts seen in polycystic liver disease may exhibit an imaging pattern similar to that of a multilocular cystic lesion. Mural nodularity, irregular thickness of the septa, ragged inner surface, and typical enhancement pattern in the solid portion of the lesion are often indicative of malignancy, although multilocular primary or secondary malignant tumors are uncommon. Recognition of the more common necrosis or cystic change of HCC and metastases induced by locoregional or systemic treatment also is important. The nonenhanced cystic component may be composed of different types of fluids (eg, serous, mucinous, proteinaceous, hemorrhagic, bilious, or mixed) or spontaneous or treatment-related necrosis, whereas the septa may be formed by a wide range of tissues depending on the lesion type. An understanding of the CT and MR imaging findings of these lesions and their respective pathologic correlation aids in accurate diagnosis.

Prediction of early response to chemotherapy in lung cancer by using diffusion-weighted MR imaging

Purpose. To determine whether change of apparent diffusion coefficient (ADC) value could predict early response to chemotherapy in lung cancer. Materials and Methods. Twenty-five patients with advanced non-small cell lung cancer underwent chest MR imaging including DWI before and at the end of the first cycle of chemotherapy. The tumor's mean ADC value and diameters on MR images were calculated and compared. The grouping reference was based on serial CT scans according to Response Evaluation Criteria in Solid Tumors. Logistic regression was applied to assess treatment response prediction ability of ADC value and diameters. Results. The change of ADC value in partial response group was higher than that in stable disease group (P = 0.004). ROC curve showed that ADC value could predict treatment response with 100% sensitivity, 64.71% specificity, 57.14% positive predictive value, 100% negative predictive value, and 82.7% accuracy. The area under the curve for combination of ADC value and longest diameter change was higher than any parameter alone (P ≤ 0.01). Conclusions. The change of ADC value may be a sensitive indicator to predict early response to chemotherapy in lung cancer. Prediction ability could be improved by combining the change of ADC value and longest diameter.

Reproducibility and Prognosis of Quantitative Features Extracted from CT Images

We study the reproducibility of quantitative imaging features that are used to describe tumor shape, size, and texture from computed tomography (CT) scans of non-small cell lung cancer (NSCLC). CT images are dependent on various scanning factors. We focus on characterizing image features that are reproducible in the presence of variations due to patient factors and segmentation methods. Thirty-two NSCLC nonenhanced lung CT scans were obtained from the Reference Image Database to Evaluate Response data set. The tumors were segmented using both manual (radiologist expert) and ensemble (software-automated) methods. A set of features (219 three-dimensional and 110 two-dimensional) was computed, and quantitative image features were statistically filtered to identify a subset of reproducible and nonredundant features. The variability in the repeated experiment was measured by the test-retest concordance correlation coefficient (CCCTreT). The natural range in the features, normalized to variance, was measured by the dynamic range (DR). In this study, there were 29 features across segmentation methods found with CCCTreT and DR ≥ 0.9 and R(2) Bet ≥ 0.95. These reproducible features were tested for predicting radiologist prognostic score; some texture features (run-length and Laws kernels) had an area under the curve of 0.9. The representative features were tested for their prognostic capabilities using an independent NSCLC data set (59 lung adenocarcinomas), where one of the texture features, run-length gray-level nonuniformity, was statistically significant in separating the samples into survival groups (P ≤ .046).

Comparison of RECIST 1.0 and RECIST 1.1 on computed tomography in patients with metastatic colorectal cancer

OBJECTIVE

We conducted this study to compare tumor measurement by computed tomography (CT) and tumor response assessment between Response Evaluation Criteria In Solid Tumors (RECIST) 1.0 and RECIST 1.1 in patients with metastatic colorectal cancer (CRC).

METHODS

We reviewed the medical records of patients with metastatic CRC who received first-line chemotherapy between January 2004 and December 2012 and compared CT tumor measurement using two RECIST versions.

RESULTS

A total of 58 patients who had target lesions according to RECIST 1.0 were included in the study. The number of target lesions recorded by RECIST 1.1 was significantly lower than that by RECIST 1.0, with a decrease experienced in 48 patients (82.7%). Six patients had no target lesions because of the new criteria of RECIST 1.1 for lymph node size. Out of 95 lymph nodes from 58 patients, only 40% were defined as target lesions according to RECIST 1.1. The overall response rate of first-line chemotherapy according to RECIST 1.0 and 1.1 was 41.5 and 40.4%, respectively. The best tumor responses showed almost perfect agreement between RECIST 1.1 and RECIST 1.0 (ĸ = 0.913). Three patients showed disagreement of the best responses between the two RECIST versions.

CONCLUSION

RECIST 1.1 showed a highly concordant response assessment with RECIST 1.0 in metastatic CRC and its clinical impact on therapeutic decisions was minimal.

Comparison of 1D, 2D, and 3D nodule sizing methods by radiologists for spherical and complex nodules on thoracic CT phantom images

RATIONALE AND OBJECTIVES

To estimate and statistically compare the bias and variance of radiologists measuring the size of spherical and complex synthetic nodules.

MATERIALS AND METHODS

This study did not require the institutional review board approval. Six radiologists estimated the size of 10 synthetic nodules embedded within an anthropomorphic thorax phantom from computed tomography scans at 0.8- and 5-mm slice thicknesses. The readers measured the nodule size using unidimensional (1D) longest in-slice dimension, bidimensional (2D) area from longest in-slice and longest perpendicular dimension, and three-dimensional (3D) semiautomated volume. Intercomparisons of bias (difference between average and true size) and variance among methods were performed after converting the 2D and 3D estimates to a compatible 1D scale.

RESULTS

The relative biases of radiologists with the 3D tool were -1.8%, -0.4%, -0.7%, -0.4%, and -1.6% for 10-mm spherical, 20-mm spherical, 20-mm elliptical, 10-mm lobulated, and 10-mm spiculated nodules compared to 1.4%, -0.1%, -26.5%, -7.8%, and -39.8% for 1D. The three-dimensional measurements were significantly less biased than 1D for elliptical, lobulated, and spiculated nodules. The relative standard deviations for 3D were 7.5%, 3.9%, 3.6%, 9.7%, and 8.3% compared to 5.7%, 2.6%, 20.3%, 5.3%, and 16.4% for 1D. Unidimensional sizing was significantly less variable than 3D for the lobulated nodule and significantly more variable for the ellipsoid and spiculated nodules. Three-dimensional bias and variability were smaller for thin 0.8-mm slice data compared to thick 5.0-mm data.

CONCLUSIONS

The study shows that radiologist-controlled 3D volumetric lesion sizing can not only achieve smaller bias but also achieve similar or smaller variability compared to 1D sizing, especially for complex lesion shapes.

Recommendations for the clinical and radiological evaluation of response to treatment in metastatic renal cell cancer

The evaluation of response to treatment is a critical step for determining the effectiveness of oncology drugs. Targeted therapies such as tyrosine kinase inhibitors and mammalian target of rapamycin inhibitors are active drugs in patients with metastatic renal cell carcinoma (mRCC). However, treatment with this type of drugs may not result in significant reductions in tumor size, so standard evaluation criteria based on tumor size, such as Response Evaluation Criteria in Solid Tumors (RECIST), may be inappropriate for evaluating response to treatment in patients with mRCC. In fact, targeted therapies apparently yield low response rates that do not reflect increased disease control they may cause and, consequently, the benefit in terms of time to progression. To improve the clinical and radiological evaluation of response to treatment in patients with mRCC treated with targeted drugs, a group of 32 experts in this field have reviewed different aspects related to this issue and have put together a series of recommendations with the intention of providing guidance to clinicians on this matter.

Consistency and efficiency of CT analysis of metastatic disease: semiautomated lesion management application within a PACS

OBJECTIVE

The purpose of this study was to evaluate the success, consistency, and efficiency of a semiautomated lesion management application within a PACS in the analysis of metastatic lesions in serial CT examinations of cancer patients.

MATERIALS AND METHODS

Two observers using baseline and follow-up CT data independently reviewed 93 target lesions (17 lung, five liver, 71 lymph node) in 50 patients with either metastatic bladder or prostate cancer. The observers measured the longest axis (or short axis for lymph nodes) of each lesion and made Response Evaluation Criteria in Solid Tumors (RECIST) determinations using manual and lesion management application methods. The times required for examination review, RECIST calculations, and data input were recorded. The Wilcoxon signed rank test was used to assess time differences, and Bland-Altman analysis was used to assess interobserver agreement within the manual and lesion management application methods. Percentage success rates were also reported.

RESULTS

With the lesion management application, most lung and liver lesions were semiautomatically segmented. Comparison of the lesion management application and manual methods for all lesions showed a median time saving of 45% for observer 1 (p<0.05) and 28% for observer 2 (p=0.05) on follow-up scans versus 28% for observer 1 (p<0.05) and 9% for observer 2 (p=0.087) on baseline scans. Variability of measurements showed mean percentage change differences of only 8.9% for the lesion management application versus 26.4% for manual measurements.

CONCLUSION

With the lesion management application method, most lung and liver lesions were successfully segmented semiautomatically; the results were more consistent between observers; and assessment of tumor size was faster than with the manual method.

Interobserver agreement of semi-automated and manual measurements of functional MRI metrics of treatment response in hepatocellular carcinoma

PURPOSE

To assess the interobserver agreement in 50 patients with hepatocellular carcinoma (HCC) before and 1 month after intra-arterial therapy (IAT) using two semi-automated methods and a manual approach for the following functional, volumetric and morphologic parameters: (1) apparent diffusion coefficient (ADC), (2) arterial phase enhancement (AE), (3) portal venous phase enhancement (VE), (4) tumor volume, and assessment according to (5) the Response Evaluation Criteria in Solid Tumors (RECIST), and (6) the European Association for the Study of the Liver (EASL).

MATERIALS AND METHODS

This HIPAA-compliant retrospective study had institutional review board approval. The requirement for patient informed consent was waived. Tumor ADC, AE, VE, volume, RECIST, and EASL in 50 index lesions was measured by three observers. Interobserver reproducibility was evaluated using intraclass correlation coefficients (ICC). P<0.05 was considered to indicate a significant difference.

RESULTS

Semi-automated volumetric measurements of functional parameters (ADC, AE, and VE) before and after IAT as well as change in tumor ADC, AE, or VE had better interobserver agreement (ICC=0.830-0.974) compared with manual ROI-based axial measurements (ICC=0.157-0.799). Semi-automated measurements of tumor volume and size in the axial plane before and after IAT had better interobserver agreement (ICC=0.854-0.996) compared with manual size measurements (ICC=0.543-0.596), and interobserver agreement for change in tumor RECIST size was also higher using semi-automated measurements (ICC=0.655) compared with manual measurements (ICC=0.169). EASL measurements of tumor enhancement in the axial plane before and after IAT ((ICC=0.758-0.809), and changes in EASL after IAT (ICC=0.653) had good interobserver agreement.

CONCLUSION

Semi-automated measurements of functional changes assessed by ADC and VE based on whole-lesion segmentation demonstrated better reproducibility than ROI-based axial measurements, or RECIST or EASL measurements.

Invited review--neuroimaging response assessment criteria for brain tumors in veterinary patients

The evaluation of therapeutic response using cross-sectional imaging techniques, particularly gadolinium-enhanced MRI, is an integral part of the clinical management of brain tumors in veterinary patients. Spontaneous canine brain tumors are increasingly recognized and utilized as a translational model for the study of human brain tumors. However, no standardized neuroimaging response assessment criteria have been formulated for use in veterinary clinical trials. Previous studies have found that the pathophysiologic features inherent to brain tumors and the surrounding brain complicate the use of the response evaluation criteria in solid tumors (RECIST) assessment system. Objectives of this review are to describe strengths and limitations of published imaging-based brain tumor response criteria and propose a system for use in veterinary patients. The widely used human Macdonald and response assessment in neuro-oncology (RANO) criteria are reviewed and described as to how they can be applied to veterinary brain tumors. Discussion points will include current challenges associated with the interpretation of brain tumor therapeutic responses such as imaging pseudophenomena and treatment-induced necrosis, and how advancements in perfusion imaging, positron emission tomography, and magnetic resonance spectroscopy have shown promise in differentiating tumor progression from therapy-induced changes. Finally, although objective endpoints such as MR imaging and survival estimates will likely continue to comprise the foundations for outcome measures in veterinary brain tumor clinical trials, we propose that in order to provide a more relevant therapeutic response metric for veterinary patients, composite response systems should be formulated and validated that combine imaging and clinical assessment criteria.

The translocator protein radioligand 18F-DPA-714 monitors antitumor effect of erufosine in a rat 9L intracranial glioma model

On the one hand, the translocator protein (TSPO) radioligand N,N-diethyl-2-(2-(4-(2-(18)F-fluoroethoxy)phenyl)-5,7-dimethylpyrazolo[1,5-a]pyrimidin-3-yl)acetamide ((18)F-DPA-714) has been suggested to serve as an alternative radiotracer to image human glioma, and on the other hand the alkylphosphocholine erufosine (ErPC3) has been reported to induce apoptosis in otherwise highly apoptosis-resistant glioma cell lines. The induction of apoptosis by ErPC3 requires TSPO, a mitochondrial membrane protein highly expressed in malignant gliomas. In this preclinical study, we monitored the effect of ErPC3 treatment in vivo using (18)F-DPA-714 PET.

METHODS

In vitro studies investigated the antitumor effect of ErPC3 in 9L rat gliosarcoma cells. In vivo, glioma-bearing rats were imaged with (18)F-DPA-714 for the time of treatment.

RESULTS

A significant decrease in 9L cell proliferation and viability and a significant increase in apoptosis and caspase-3 activation were demonstrated on ErPC3 treatment in cell culture. In the rat model, ErPC3 administration resulted in significant changes in (18)F-DPA-714 tumor uptake over the course of the treatment. Immunohistochemistry revealed reduced tumor volume and increased cell death in ErPC3-treated animals accompanied by infiltration of the tumor core by CD11b-positive microglia/macrophages and glial fibrillary acidic protein-positive astrocytes.

CONCLUSION

Our findings demonstrate a potent antitumor effect of ErPC3 in vitro, in vivo, and ex vivo. PET imaging of TSPO expression using (18)F-DPA-714 allows effective monitoring and quantification of disease progression and response to ErPC3 therapy in intracranial 9L gliomas.

Impact of slice thickness on semi-automated measurements for volume and whole-tumor attenuation of colorectal hepatic metastases in multislice computed tomography

BACKGROUND

Volumetric and whole-tumor attenuation assessment of tumor are of value in assessment of treatment.

PURPOSE

To assess the impact of slice thickness on semi-automatic analyses (volume, whole-tumor attenuation) for small colorectal hepatic metastases.

MATERIAL AND METHODS

Computed tomography (CT) data of patients with colorectal hepatic metastases at 1.5-, 3-, and 5-mm slice thickness were semi-automatically evaluated for volume and whole-tumor attenuation by two radiologists independently. Statistical analysis included paired samples t-test and concordance correlation coefficient (CCC) analysis according to the longest axial tumor diameter (10-20 mm, 20-30 mm, 30-40 mm).

RESULTS

A total of 62 patients (32 men and 30 women) with 62 target tumors were included. The mean volume was significantly higher at 3- and 5-mm slice thicknesses in comparison with the reference (1.5 mm) for the target tumors between 10 mm and 20 mm (P = 0.0295, CCC = 0.9394 for 3 mm; P = 0.0029, CCC = 0.5129 for 5 mm, respectively) and at 5 mm slice thickness for the target tumors between 20 mm and 30 mm (P = 0.0071, CCC = 0.9102). For whole-tumor attenuation measurements, the significant difference was only seen at 5-mm slice thicknesses in comparison with the reference (1.5 mm) for the target tumors between 10 and 20 mm (P = 0.0015, CCC = 0.9389).

CONCLUSION

Slice thickness of 1.5 mm might be suggested for semi-automated volumetric measurements, and slice thickness of no more than 3 mm for whole-tumor CT attenuation in hepatic metastasis between 10 mm and 20 mm.