Adrianus J. de Langen

Repeatability of Metabolically Active Volume Measurements with 18F-FDG and 18F-FLT PET in Non–Small Cell Lung Cancer

In addition to tumor size measurements with CT, there is a need for quantitative measurements of metabolic active volumes, possibly adding to tracer uptake measurements in oncologic response evaluation with PET. The aim of this study was to evaluate the metabolic volume test–retest variability in 18F-FDG and 3′-deoxy-3′-18F-fluorothymidine (18F-FLT) PET studies for various commonly used volumes of interest (VOIs) and the dependence of that variability on lesion size and relative radiotracer uptake. Methods: Twenty non–small cell lung cancer patients were scanned twice with 18F-FDG (n = 11) or 18F-FLT (n = 9). VOIs were defined on images reconstructed with normalization- and attenuation-weighted ordered-subset expectation maximization using 4 isocontours (A41%, A50%, and A70% thresholds, adapted for local background, and 50% threshold, uncorrected for background). Statistical analysis comprised intraclass correlation coefficients and Bland–Altman analysis. Results: In the 18F-FDG and 18F-FLT groups, 34 and 20 lesions, respectively, were analyzed. Median volumes at the A50% threshold were 3.31 and 2.19 mL (interquartile range, 1.91–8.90 and 1.52–7.27 mL) for 18F-FDG and 18F-FLT, respectively. Intraclass correlation coefficients were greater than 0.9, with the exception of the A70%-based metabolic volumes for 18F-FLT. For lesions greater than 4.2 mL, repeatability coefficients (RCs = 1.96 × SD) of the percentage difference ranged from 22% to 37% for 18F-FDG and from 39% to 73% for 18F-FLT, depending on the VOI method being used. Repeatability was better for larger tumors, but there was no dependence on absolute uptake (standardized uptake value). Conclusion: Results indicate that changes of greater than 37% for 18F-FDG and greater than 73% for 18F-FLT (1.96 × SD) for lesions with A50% metabolic volumes greater than 4.2 mL represent a biologic effect. For smaller lesions (A50% VOI < 4.2 mL), an absolute change of 1.0 and 0.9 mL for 18F-FDG and 18F-FLT, respectively, is biologically relevant. Considering the balance between the success rate of automatic tumor delineation and repeatability of metabolic volume, a 50% threshold with correction for local background activity (A50%) seems optimal among the VOI methods evaluated.

Monitoring Response to Antiangiogenic Therapy in Non–Small Cell Lung Cancer Using Imaging Markers Derived from PET and Dynamic Contrast-Enhanced MRI

With antiangiogenic agents, tumor shrinkage may be absent, despite survival benefit. The present study assessed the predictive value of molecular imaging for the identification of survival benefit during antiangiogenic treatment with bevacizumab and erlotinib in patients with advanced non–small cell lung cancer. Methods: Patients were evaluated using an imaging protocol including CT, 18F-FDG PET, H215O PET, and dynamic contrast-enhanced MRI to derive measurements on tumor size, glucose metabolism, perfusion, and microvascular permeability. The percentage change in imaging parameters after 3 wk of treatment as compared with baseline was calculated and correlated with progression-free survival (PFS). Results: Forty-four patients were included, and 40 underwent CT and 18F-FDG PET at both time points. Complete datasets, containing all imaging modalities, were available for 14 patients. Bevacizumab and erlotinib treatment resulted in decreased metabolism, perfusion, and tumor size. A decrease in standardized uptake value or tumor perfusion of more than 20% at week 3 was associated with longer PFS (9.7 vs. 2.8 mo, P = 0.01, and 12.5 vs. 2.9 mo, P = 0.009, respectively). Whole-tumor Ktrans (the endothelial transfer constant) was not associated with PFS, but patients with an increase of more than 15% in the SD of tumor Ktrans values—that is, an increase in regions with low or high Ktrans values—after 3 wk had shorter PFS (2.3 vs. 7.0 mo, P = 0.008). A partial response, according to the response evaluation criteria in solid tumors (RECIST), at week 3 was also associated with prolonged PFS (4.6 vs. 2.9 mo, P = 0.017). However, 40% of patients with a partial response as their best RECIST response still had stable disease at week 3. In these cases tumor perfusion was already decreased and Ktrans heterogeneity showed no increase, indicating that the latter parameters seem to be more discriminative than RECIST at the 3-wk time point. Conclusion: PET and dynamic contrast-enhanced MRI were able to identify patients who benefit from bevacizumab and erlotinib treatment. Molecular imaging seems to allow earlier response evaluation than CT.

Use of H215O-PET and DCE-MRI to Measure Tumor Blood Flow

Positron emission tomography (PET) with H2(15)O and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) provide noninvasive measurements of tumor blood flow. Both tools offer the ability to monitor the direct target of antiangiogenic treatment, and their use is increasingly being studied in trials evaluating such drugs. Antiangiogenic therapy offers great potential and, to an increasing extent, benefit for oncological patients in a variety of palliative and curative settings. Because this type of targeted therapy frequently results in consolidation of the tumor mass instead of regression, monitoring treatment response with the standard volumetric approach (Response Evaluation Criteria in Solid Tumors) leads to underestimation of the response rate. Monitoring direct targets of anticancer therapy might be superior to indirect size changes. In addition, measures of tumor blood flow contribute to a better understanding of tumor biology. This review shows that DCE-MRI and H2(15)O-PET provide reliable measures of tumor perfusion, provided that a certain level of standardization is applied. Heterogeneity in scan acquisition and data analysis complicates the interpretation of study results. Also, limitations inherent to both techniques must be considered when interpreting DCE-MRI and H2(15)O-PET results. This review focuses on the technical and physiological aspects of both techniques and aims to provide the essential information necessary to critically evaluate the use of DCE-MRI and H2(15)O-PET in an oncological setting.

Repeatability of Radiomic Features in Non-Small-Cell Lung Cancer [18F]FDG-PET/CT Studies: Impact of Reconstruction and Delineation

PurposeTo assess (1) the repeatability and (2) the impact of reconstruction methods and delineation on the repeatability of 105 radiomic features in non-small-cell lung cancer (NSCLC) 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) positron emission tomorgraphy/computed tomography (PET/CT) studies.ProceduresEleven NSCLC patients received two baseline whole-body PET/CT scans. Each scan was reconstructed twice, once using the point spread function (PSF) and once complying with the European Association for Nuclear Medicine (EANM) guidelines for tumor PET imaging. Volumes of interest (n = 19) were delineated twice, once on PET and once on CT images.ResultsSixty-three features showed an intraclass correlation coefficient ≥ 0.90 independent of delineation or reconstruction. More features were sensitive to a change in delineation than to a change in reconstruction (25 and 3 features, respectively).ConclusionsThe majority of features in NSCLC [18F]FDG-PET/CT studies show a high level of repeatability that is similar or better compared to simple standardized uptake value measures.

Effects of Image Characteristics on Performance of Tumor Delineation Methods: A Test–Retest Assessment

PET can be used to monitor response during chemotherapy and assess biologic target volumes for radiotherapy. Previous simulation studies have shown that the performance of various automatic or semiautomatic tumor delineation methods depends on image characteristics. The purpose of this study was to assess test–retest variability of tumor delineation methods, with emphasis on the effects of several image characteristics (e.g., resolution and contrast). Methods: Baseline test–retest data from 19 non–small cell lung cancer patients were obtained using 18F-FDG (n = 10) and 3′-deoxy-3′-18F-fluorothymidine (18F-FLT) (n = 9). Images were reconstructed with varying spatial resolution and contrast. Six different types of tumor delineation methods, based on various thresholds or on a gradient, were applied to all datasets. Test–retest variability of metabolic volume and standardized uptake value (SUV) was determined. Results: For both tracers, size of metabolic volume and test–retest variability of both metabolic volume and SUV were affected by the image characteristics and tumor delineation method used. The median volume test–retest variability ranged from 8.3% to 23% and from 7.4% to 29% for 18F-FDG and 18F-FLT, respectively. For all image characteristics studied, larger differences (≤10-fold higher) were seen in test–retest variability of metabolic volume than in SUV. Conclusion: Test–retest variability of both metabolic volume and SUV varied with tumor delineation method, radiotracer, and image characteristics. The results indicate that a careful optimization of imaging and delineation method parameters is needed when metabolic volume is used, for example, as a response assessment parameter.

Reproducibility of Tumor Perfusion Measurements Using 15O-Labeled Water and PET

PET and 15O-labeled water (H215O) can be used to noninvasively monitor tumor perfusion. This allows evaluation of the direct target of antiangiogenic drugs, that is, tumor vasculature. Because these drugs often result in consolidation rather than regression of the tumor mass, a change in perfusion might be a more sensitive way to evaluate response than are indirect size measures on a CT scan. However, to use the technique for serial imaging of individual patients, good reproducibility is essential. The purpose of the present study was to evaluate the reproducibility of quantitative H215O measurements. Methods: Nine patients with non–small-cell lung cancer (NSCLC) were scanned twice within 7 d and before any therapy. All H215O scans were followed by an 18F-fluorothymidine scan to allow for adequate volume-of-interest (VOI) definition. VOIs were defined using a 3-dimensional threshold technique. Tumor perfusion and the volume of distribution (VT) were obtained using a 1-tissue-compartment model including an arterial blood volume component and an image-derived input function. The level of agreement between test and retest values was assessed using the intraclass correlation coefficient (ICC) and Bland–Altman analyses. Possible dependency on absolute values and lesion size was assessed by linear regression. Results: All primary tumors and more than 90% of clinically suspected locoregional metastases could be delineated. In total, 14 lesions in 9 patients were analyzed. Tumor perfusion showed excellent reproducibility, with an ICC of 0.95 and SD of 9%. The VT was only moderately reproducible, with an ICC of 0.52 and SD of 16%. No dependency was found on absolute values of perfusion (P = 0.14) and VT (P = 0.15). In addition, tumor volume did not influence the reproducibility of perfusion (P = 0.46) and VT (P = 0.25). Conclusion: Quantitative measurements of tumor perfusion using H215O and PET are reproducible in NSCLC. When patients are repeatedly being scanned during therapy, changes of more than 18% in tumor perfusion and 32% in VT (>1.96 × SD) are likely to represent treatment effects.

Outcomes of Hypofractionated High-Dose Radiotherapy in Poor-Risk Patients with “Ultracentral” Non–Small Cell Lung Cancer

Introduction: We defined “ultracentral” lung tumors as centrally located non–small cell lung cancers with planning target volumes overlapping the trachea or main bronchi. Increased toxicity has been reported after both conventional and stereotactic radiotherapy for such lesions. We studied outcomes after 12 fractions of 5 Gy (BED10 = 90 Gy, heterogeneous dose distribution) to ultracentral tumors in patients unfit for surgery or conventional chemoradiotherapy. Methods: Clinical outcomes and dosimetric details were analyzed in 47 consecutive patients with single primary or recurrent ultracentral non–small cell lung cancer treated between 2010 and 2015. Those irradiated previously or with metastasis to sites other than the brain and adrenal glands were excluded. Treatments were delivered using volumetric modulated arc therapy. Results: The median age was 77.5 years, 49% of patients had a World Health Organization performance score of 2 or higher, and the median planning target volume was 104.5cm3 (range 17.7–508.5). At a median follow‐up of 29.3 months, median overall survival was 15.9 months, and 3‐year survival was 20.1%. No isolated local recurrences were observed. Grade 3 or higher toxicity was recorded in 38% of patients, with 21% scored as having a “possible” (n = 2) or “likely” (n = 8) treatment‐related death between 5.2 and 18.2 months after treatment. Fatal pulmonary hemorrhage was observed in 15% of patients. Conclusions: Unfit patients with ultracentral tumors who were treated using this scheme had a high local control and a median survival of 15.9 months. Despite manifestation of rates of a fatal lung bleeding comparable to those seen with conventional radiotherapy for endobronchial tumors, the overall rate of G5 toxicity is of potential concern. Additional work is needed to identify tumor and treatment factors related to hemorrhage.

Treatment and survival of patients with EGFR-mutated non-small cell lung cancer and leptomeningeal metastasis: A retrospective cohort analysis

OBJECTIVES Development of leptomeningeal metastasis (LM) in non-small cell lung cancer (NSCLC)-patients is associated with a poor prognosis. It has been suggested that LM-patients with epidermal growth factor receptor mutated (EGFR+) NSCLC have a superior prognosis compared to EGFR-wild type NSCLC. Studies in EGFR+ NSCLC-patients with LM are scarce. We retrospectively evaluated a multi-institutional cohort of EGFR+ NSCLC-patients for LM to assess clinical outcome in relation to patient characteristics and treatment modalities. MATERIAL AND METHODS Medical records of advanced-stage EGFR+ NSCLC-patients (diagnosed between August 2000 and June 2014) from 11 Dutch hospitals were evaluated for LM as diagnosed by MRI and/or cytopathological liquor analysis. Data on patient characteristics, treatment and outcome were collected. RESULTS Thirty-two of 356 (9.0%) advanced-stage EGFR+ NSCLC-patients (median follow-up 21.0 months), were diagnosed with LM between 2006 and 2014. LM was diagnosed by MRI (59.4%), liquor analysis (9.4%) or by both MRI and liquor analysis (31.3%). Median survival after LM-diagnosis was 3.1 months (95% CI: 0.0-7.3). Six- and 12-month survival rates were 43.8% and 18.8%, respectively. Patients with performance status (PS) 0-1 at time of diagnosis of LM had a significantly higher chance to be alive after 6 months and had a significantly longer survival after diagnosis of LM compared to patients with PS≥2. Age, treatment with high-dose EGFR-TKI, radiotherapy and whether LM was the only site of progressive disease did not influence survival after LM-diagnosis. CONCLUSION Although median survival after LM-diagnosis in EGFR-mutated NSCLC-patients was poor, a substantial part of the patients had a prolonged survival of more than 6 months. PS of 0-1 at time of diagnosis of LM was associated with prolonged survival. No other patient- or treatment-related characteristics were identified. Further research is warranted to identify treatment strategies that improve survival in EGFR+ NSCLC-patients with LM.

Swarm Intelligence-Enhanced Detection of Non-Small-Cell Lung Cancer Using Tumor-Educated Platelets

Summary Blood-based liquid biopsies, including tumor-educated blood platelets (TEPs), have emerged as promising biomarker sources for non-invasive detection of cancer. Here we demonstrate that particle-swarm optimization (PSO)-enhanced algorithms enable efficient selection of RNA biomarker panels from platelet RNA-sequencing libraries (n = 779). This resulted in accurate TEP-based detection of early- and late-stage non-small-cell lung cancer (n = 518 late-stage validation cohort, accuracy, 88%; AUC, 0.94; 95% CI, 0.92–0.96; p < 0.001; n = 106 early-stage validation cohort, accuracy, 81%; AUC, 0.89; 95% CI, 0.83–0.95; p < 0.001), independent of age of the individuals, smoking habits, whole-blood storage time, and various inflammatory conditions. PSO enabled selection of gene panels to diagnose cancer from TEPs, suggesting that swarm intelligence may also benefit the optimization of diagnostics readout of other liquid biopsy biosources.

Repeatability of Quantitative Whole Body 18F-FDG PET/CT Uptake Measures as Function of Uptake Interval and Lesion Selection in Non-Small Cell Lung Cancer Patients.

Change in 18F-FDG uptake may predict response to anticancer treatment. The PERCIST suggest a threshold of 30% change in SUV to define partial response and progressive disease. Evidence underlying these thresholds consists of mixed stand-alone PET and PET/CT data with variable uptake intervals and no consensus on the number of lesions to be assessed. Additionally, there is increasing interest in alternative 18F-FDG uptake measures such as metabolically active tumor volume and total lesion glycolysis (TLG). The aim of this study was to comprehensively investigate the repeatability of various quantitative whole-body 18F-FDG metrics in non–small cell lung cancer (NSCLC) patients as a function of tracer uptake interval and lesion selection strategies. Methods: Eleven NSCLC patients, with at least 1 intrathoracic lesion 3 cm or greater, underwent double baseline whole-body 18F-FDG PET/CT scans at 60 and 90 min after injection within 3 d. All 18F-FDG–avid tumors were delineated with an 50% threshold of SUVpeak adapted for local background. SUVmax, SUVmean, SUVpeak, TLG, metabolically active tumor volume, and tumor-to-blood and -liver ratios were evaluated, as well as the influence of lesion selection and 2 methods for correction of uptake time differences. Results: The best repeatability was found using the SUV metrics of the averaged PERCIST target lesions (repeatability coefficients < 10%). The correlation between test and retest scans was strong for all uptake measures at either uptake interval (intraclass correlation coefficient > 0.97 and R2 > 0.98). There were no significant differences in repeatability between data obtained 60 and 90 min after injection. When only PERCIST-defined target lesions were included (n = 34), repeatability improved for all uptake values. Normalization to liver or blood uptake or glucose correction did not improve repeatability. However, after correction for uptake time the correlation of SUV measures and TLG between the 60- and 90-min data significantly improved without affecting test–retest performance. Conclusion: This study suggests that a 15% change of SUVmean/SUVpeak at 60 min after injection can be used to assess response in advanced NSCLC patients if up to 5 PERCIST target lesions are assessed. Lower thresholds could be used in averaged PERCIST target lesions (<10%).