Reproducibility and uptake time dependency of volume-based parameters on FDG-PET for lung cancer

The prognostic value of positron emission tomography/magnetic resonance imaging in predicting survival in patients with adenocarcinoma of the esophagogastric junction

INTRODUCTION

In recent years, the utility of positron emission tomography/magnetic resonance imaging (PET/MRI) has become increasingly significant in diagnostic settings. This study provides a five-year follow-up on a previous pilot study that demonstrated the feasibility of PET/MRI in predicting the resectability of adenocarcinoma of the esophagogastric junction (AEG). We aimed to evaluate whether this imaging modality could further serve as a prognostic tool for survival in AEG patients.

METHODS

A total of 22 patients were included in the initial pilot study, with 17 of them undergoing surgery. All patients underwent three series of neo-adjuvant chemotherapy (NT). This follow-up study retrospectively analyzed the correlation between the apparent diffusion coefficient (ADC) and standard uptake value (SUV) measurements of the primary tumor from the original study with overall survival and recurrence. ADC and SUV values were measured prior to initiation of NT, and again 17-21 days into the first cycle of NT-administration, and the differences between the scans were calculated as ∆SUVmax, ∆ADCb0, and ∆ADCb50. Early treatment response was assessed using the Response Evaluation Criteria In Solid Tumors (RECIST). Binary logistic regression was employed to evaluate the predictive values of ADC and SUV parameters, and receiver operating characteristic (ROC) curves were generated to determine sensitivity, specificity, and area under the curve (AUC).

RESULTS

As of January 7, 2022, 8 of the 22 patients were still alive. The AUC was calculated to assess the association of imaging parameters with long-term survival: ∆SUVmax: AUC = 0.74, sensitivity, 87.5%, specificity 62.5% (p = 0.037). ∆ADCb0: AUC = 0.62, sensitivity 85.7%, specificity 57.1% (p = 0.400). ∆ADCb50: AUC = 0.78, sensitivity 78.6%, specificity 85.7% (p = 0.011). Combining all three parameters yielded an AUC of 0.81, with a sensitivity of 78.6% and a specificity of 85.7% (p = 0.002). The results for individual measurements were: SUVmax(pre-NT): AUC = 0.56, sensitivity 78.6%, specificity 50% (p = 0.646). SUVmax(post-NT): AUC = 0.81, sensitivity 85.7%, specificity 87.5% (p = 0.002). ADCb0(pre-NT): AUC = 0.55, sensitivity 71.4%, specificity 62.5% (p = 0.682). ADCb0(post-NT): AUC = 0.63, sensitivity 78.6%, specificity 57.1% (p = 0.339). ADCb50(pre-NT): AUC = 0.51, sensitivity 85.7%, specificity 37.5% (p = 0.952). ADCb50(post-NT): AUC = 0.63, sensitivity 42.9%, specificity 100% (p = 0.279). No significant correlation was found between RECIST group and survival status (p = 0.15).

CONCLUSION

Our results indicate that PET/MRI is feasible for predicting long-term survival in AEG patients. The highest AUCs were achieved when combining SUV and ADC parameters, and when using post-NT SUVmax alone.

PET-based Quantitative Techniques in Assessing Efficacy of Interventional Radiology Procedures in Oncology

Interventional radiology (IR) is a super specialised branch where imaging modalities are employed to guide disease specific diagnostic and therapeutic interventions. IR interventions have gained popularity in various oncological and non-oncological indications due to it's ability to effectively diagnose the disease and direct specific targeted treatment. Hybrid imaging using PET CT and PET MRI combines the best of morphological and functional informations and offers improved sensitivity and specificity for detection of lesion; helps in accurate mapping of tumour burden, thereby aiding in planning curative vs palliative intent intervention; more accurate response evaluation to plan redo session in cases of residual / recurrent disease or for follow up evaluation and for prognostication and predicting response. Albeit visual analysis of PET images by specialist is most commonly performed for reading PET scans, PET has a remarkable capability to provide quantitative information. The present review provides a comprehensive assessment of the role of various aspects of quantitative PET parameters in assessing the efficacy of IR interventions. The insights provided will help clinicians, researchers, and medical professionals understand the role of PET imaging in advancing patient care and enhancing the therapeutic outcomes of IR procedures.

Prognostic value of pretreatment FDG PET-CT for short-term efficacy of radioactive iodine-125 seed implantation in patients with NSCLC

PURPOSE

To analyze the short-term clinical response of radioactive iodine-125 seed implantation (I125-SI) in patients of non-small-cell lung cancer (NSCLC) and explore possible correlations of various metabolic parameters of pretreatment FDG PET-CT with the short-term efficacy of this treatment modality.

METHODS AND MATERIALS

The present study is a retrospective analysis of treatment records of 46 NSCLC patients who were treated with I125-SI for lung tumors in Tianjin First Central Hospital from January 2016 to December 2018. The correlation among parameters D90, gender, pathological pattern, age, maximum tumor diameter, Metabolic Tumor Volume (MTV), SUVmax, SUVpeak, SUVmean, Total Lesion Glycolysis (TLG), High metabolic tumor cell ratio (HMR) and Carcinoembryonic antigen(CEA)with short-term efficacy of I125-SI was analyzed by two independent-sample t-test, Mann-Whitney U test or Chi-squared test and binary logistic regression.

RESULTS

After uneventful completion of treatment, patients were followed up at regular intervals. At the first month followup, none of cases showed complete response (CR), while 4 cases showed partial response (PR). After 3 months, there were 2 cases of CR, and 25 cases of PR; after 6 months, there were 5 cases of CR, and 27 cases of PR. D90 (p= 0.028, OR:1.075, 95% CI:1.008-1.147), MTV (p= 0.026, OR: 0.918, 95% CI: 0.851-0.990), HMR (p= 0.020, OR: 0.003, 95% CI: 0-0.407) were independent predictors for the short-term efficacy. The predictive accuracy of MTV was medium (AUC = 0.781; cutoff value = 44.58). However, the predictive accuracies of D90 and HMR were low, with the values of AUC being 0.650 for both the parameters, and their cutoff values being 127.8 Gy and 0.27 respectively.

CONCLUSIONS

I125-SI is an effective therapy with few complications in NSCLC patients. Small MTV, high D90 and low HRM were found to be linked with better local control at 6 months postimplantation.

Metabolic bulk volume predicts survival in a homogeneous cohort of stage II/III diffuse large B-cell lymphoma patients undergoing R-CHOP treatment

Purpose

Accurate risk stratification can improve lymphoma management, but current volumetric ¹⁸F-fluorodeoxyglucose (FDG) indicators require time-consuming segmentation of all lesions in the body. Herein, we investigated the prognostic values of readily obtainable metabolic bulk volume (MBV) and bulky lesion glycolysis (BLG) that measure the single largest lesion.

Methods

The study subjects were a homogeneous cohort of 242 newly diagnosed stage II or III diffuse large B-cell lymphoma (DLBCL) patients who underwent first-line R-CHOP treatment. Baseline PET/CT was retrospectively analyzed for maximum transverse diameter (MTD), total metabolic tumor volume (TMTV), total lesion glycolysis (TLG), MBV, and BLG. Volumes were drawn using 30% SUVmax as threshold. Kaplan-Meier survival analysis and the Cox proportional hazards model assessed the ability to predict overall survival (OS) and progression-free survival (PFS).

Results

During a median follow-up period of 5.4 years (maximum of 12.7 years), events occurred in 85 patients, including progression, relapse, and death (65 deaths occurred at a median of 17.6 months). Receiver operating characteristic (ROC) analysis identified an optimal TMTV of 112 cm³, MBV of 88 cm³, TLG of 950, and BLG of 750 for discerning events. Patients with high MBV were more likely to have stage III disease; worse ECOG performance; higher IPI risk score; increased LDH; and high SUVmax, MTD, TMTV, TLG, and BLG. Kaplan-Meier survival analysis showed that high TMTV (p = 0.005 and < 0.001), MBV (both p < 0.001), TLG (p < 0.001 and 0.008), and BLG (p = 0.018 and 0.049) were associated with significantly worse OS and PFS. On Cox multivariate analysis, older age (> 60 years; HR, 2.74; 95% CI, 1.58-4.75; p < 0.001) and high MBV (HR, 2.74; 95% CI, 1.05-6.54; p = 0.023) were independent predictors of worse OS. Older age (hazard ratio [HR], 2.90; 95% CI, 1.74-4.82; p < 0.001) and high MBV (HR, 2.36; 95% CI, 1.15-6.54; p = 0.032) were also independent predictors of worse PFS. Furthermore, among subjects ≤60 years, high MBV remained the only significant independent predictor of worse OS (HR, 4.269; 95% CI, 1.03-17.76; p = 0.046) and PFS (HR, 6.047; 95% CI, 1.73-21.11; p = 0.005). Among subjects with stage III disease, only greater age (HR, 2.540; 95% CI, 1.22-5.30; p = 0.013) and high MBV (HR, 6.476; 95% CI, 1.20-31.9; p = 0.030) were significantly associated with worse OS, while greater age was the only independent predictor of worse PFS (HR, 6.145; 95% CI, 1.10-4.17; p = 0.024).

Conclusions

MBV easily obtained from the single largest lesion may provide a clinically useful FDG volumetric prognostic indicator in stage II/III DLBCL patients treated with R-CHOP.

FDG-PET/CT in the Monitoring of Lymphoma Immunotherapy Response: Current Status and Future Prospects

Cancer immunotherapy has been extensively investigated in lymphoma over the last three decades. This new treatment modality is now established as a way to manage and maintain several stages and subtypes of lymphoma. The establishment of this novel therapy has necessitated the development of new imaging response criteria to evaluate and follow up with cancer patients. Several FDG PET/CT-based response criteria have emerged to address and encompass the various most commonly observed response patterns. Many of the proposed response criteria are currently being used to evaluate and predict responses. The purpose of this review is to address the efficacy and side effects of cancer immunotherapy and to correlate this with the proposed criteria and relevant patterns of FDG PET/CT in lymphoma immunotherapy as applicable. The latest updates and future prospects in lymphoma immunotherapy, as well as PET/CT potentials, will be discussed.

The reproducibility of MTV and TLG of soft tissue tumors calculated by FDG-PET: Comparison between the lower limit by the fixed value SUV 2.5 and that value by 30% of SUVmax

PURPOSE

We evaluated the reproducibility calculating volume-based FDG-PET/CT parameters, i.e., metabolic tumor volume (MTV) and total lesion glycolysis (TLG), in soft tissue tumors.

MATERIALS AND METHODS

Fifty-three cases with soft tissue tumors were analyzed retrospectively. The conditions determining the lower limit of MTV were fixed value SUV 2.5 or 30% of SUVmax. To investigate the agreement of the measurements by two radiologists, %difference, the correlation coefficients and Bland-Altman plot were analyzed. We compared these parameters in both intra- and inter-operator for evaluating the agreement in the measurements.

RESULTS

The values of % difference were excellent, 0.2-3.5%, in the intra-operator in all calculated volume-based parameters. In both inter- and intra-operator analysis, the values of % differences were lower in the parameters calculated by SUV 2.5 fixed value as a lower threshold compared with those calculated by 30% of SUVmax as a lower threshold. The correlation coefficient in MTV30% for inter-operator were 0.84 or 0.87, those were lower than values by the intra-operator evaluation. Nevertheless, the correlation coefficients were higher than 0.84 in every parameter. Particularly, correlation coefficient in the parameters calculated by SUV 2.5 fixed value was better than those calculated by 30% of SUVmax. The Bland-Altman plot analysis showed good agreement for all parameters, particularly in the intra-operator examinations. However, in the inter-operator study, some variances were noted in every condition.

CONCLUSION

In conclusion, the reproducibility of measuring volume-based FDG-PET/CT parameters of soft tissue tumors was good, particularly, in the measurement by fixed lower limit value SUV 2.5 in the intra-operator.

Early Prediction of Radiotherapeutic Efficacy in a Mouse Model of Non-Small Cell Lung Carcinoma Using 18F-FLT and 18F-FDG PET/CT

This study investigated the usefulness of [18F]-3'-deoxy-3'-fluorothymidine (18F-FLT) and [18F]-fluoro-2-deoxy-D-glucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT) imaging for predicting the therapeutic efficacy of non-small cell lung cancer (NSCLC) irradiation at an early stage after radiation treatment. Mice were xenografted with the human lung adenocarcinoma line A549 or large cell lung cancer line FT821. Tumour uptake of 18F-FLT and 18F-FDG was imaged using PET/CT before and 1 week after irradiation. In A549 tumours, 18F-FLT uptake was significantly decreased, and 18F-FDG uptake was unchanged post-irradiation compared with pre-irradiation. In FT821 tumours, uptake of both 18F-FLT and 18F-FDG uptake was substantially decreased post-irradiation compared with pre-irradiation. In both xenografts, tumour volumes in the irradiated groups were significantly decreased compared with those in the control group. 18F-FLT is expected to contribute to individual NSCLC therapy because it accurately evaluates the decrease in tumour activity that cannot be captured by 18F-FDG. 18F-FDG may be useful for evaluating surviving cells without being affected by the inflammatory reaction at an extremely early stage, approximately 1 week after irradiation. Combined use of 18F-FLT and 18F-FDG PET/CT imaging may increase the accurate prediction of radiotherapy efficacy, which may lead to improved patient outcomes and minimally invasive personalised therapy. J. Med. Invest. 70 : 361-368, August, 2023.

Reproducibility of Standardized Uptake Values Including Volume Metrics Between TOF-PET-MR and TOF-PET-CT

Purpose

To investigate the reproducibility of tracer uptake measurements, including volume metrics, such as metabolic tumor volume (MTV) and tumor lesion glycolysis (TLG) obtained by TOF-PET-CT and TOF-PET-MR.

Materials and Methods

Eighty consecutive patients with different oncologic diagnoses underwent TOF-PET-CT (Discovery 690; GE Healthcare) and TOF-PET-MR (SIGNA PET-MR; GE Healthcare) on the same day with single dose−18F-FDG injection. The scan order, PET-CT following or followed by PET-MR, was randomly assigned. A spherical volume of interest (VOI) of 30 mm was placed on the liver in accordance with the PERCIST criteria. For liver, the maximum and mean standard uptake value for body weight (SUV) and lean body mass (SUL) were obtained. For tumor delineation, VOI with a threshold of 40 and 50% of SUVmax was used (VOI40 and VOI50). The SUVmax, SUVmean, SUVpeak, MTV and TLG were calculated. The measurements were compared between the two scanners.

Results

In total, 80 tumor lesions from 35 patients were evaluated. There was no statistical difference observed in liver regions, whereas in tumor lesions, SUVmax, SUV mean, and SUVpeak of PET-MR were significantly underestimated (p < 0.001) in both VOI40 and VOI50. Among volume metrics, there was no statistical difference observed except TLG on VOI50 (p = 0.03). Correlation between PET-CT and PET-MR of each metrics were calculated. There was a moderate correlation of the liver SUV and SUL metrics (r = 0.63–0.78). In tumor lesions, SUVmax and SUVmean had a stronger correlation with underestimation in PET-MR on VOI 40 (SUVmax and SUVmean; r = 0.92 and 0.91 with slope = 0.71 and 0.72, respectively). In the evaluation of MTV and TLG, the stronger correlations were observed both on VOI40 (MTV and TLG; r = 0.75 and 0.92) and VOI50 (MTV and TLG; r = 0.88 and 0.95) between PET-CT and PET-MR.

Conclusion

PET metrics on TOF-PET-MR showed a good correlation with that of TOF-PET-CT. SUVmax and SUVpeak of tumor lesions were underestimated by 16% on PET-MRI. MTV with % threshold can be regarded as identical volumetric markers for both TOF-PET-CT and TOF-PET-MR.

Influences on PET Quantification and Interpretation

Various factors have been identified that influence quantitative accuracy and image interpretation in positron emission tomography (PET). Through the continuous introduction of new PET technology-both imaging hardware and reconstruction software-into clinical care, we now find ourselves in a transition period in which traditional and new technologies coexist. The effects on the clinical value of PET imaging and its interpretation in routine clinical practice require careful reevaluation. In this review, we provide a comprehensive summary of important factors influencing quantification and interpretation with a focus on recent developments in PET technology. Finally, we discuss the relationship between quantitative accuracy and subjective image interpretation.

Utility of Volumetric Metabolic Parameters on Preoperative FDG PET/CT for Predicting Tumor Lymphovascular Invasion in Non-Small Cell Lung Cancer

Background: Lymphovascular invasion (LVI) is an adverse prognostic indicator in non-small cell lung cancer (NSCLC) and serves as an indication for postoperative adjuvant chemotherapy recommendation after resection. Objective: To assess the utility of clinicopathologic factors and volumetric metabolic parameters from preoperative FDG PET/CT in predicting primary tumor LVI in NSCLC. Methods: This retrospective study included 161 patients (mean age, 61.8±8.1 years; 111 men, 50 women) with surgically-confirmed NSCLC who underwent preoperative FDG PET/CT between January 2018 and November 2020. Two nuclear medicine physicians used software to place automated volumes of interest delineating each tumor to record metabolic indices (SUVmax, SUVmean, and metabolictumor volume [MTV]), which in turn were used to calculate total lesion glycolysis (TLG). Measurements were first performed independently to determine interobserver agreement using intraclass correlation coefficients (ICCs) and then repeated in consensus. Associations of clinicopathologic and metabolic parameters with tumor LVI status were assessed using t test, Mann-Whitney U test, and chi-squared test. Diagnostic performance was assessed using ROC analysis. Multivariable logistic regression analysis was performed to identify independent predictors of tumor LVI. Results: A total of 23.6% (38/161) of patients had LVI. Interobserver agreement was ICC=1.000 for SUVmax, ICC=0.997 for SUVmean, and 0.999 for MTV. Tumors with LVI, compared with tumors without LVI, exhibited higher SUVmax (15.4±5.9 vs 11.7±7.5, p=.006), SUVmean (6.0±1.6 vs 5.1±2.0, p=.009), MTV (median 15.8 cm3 vs 5.5 cm3, p<.001), and TLG (median 88.8 vs 24.5, p<.001). Among the metabolic parameters, AUC was highest for MTV (0.704), with optimal MTV cutoff of 6.4 cm3 yielding sensitivity 92.1% (35/38), specificity 56.1% (69/123), PPV 39.3% (35/89), and NPV 95.8% (69/72) for LVI. Independent predictors (p<.05) of LVI were MTV (≥6.4 cm3, odds ratio [OR]=6.5), N1 (OR=6.4) or N2 (OR=4.0) disease, and T2 disease (OR=3.6). These factors combined achieved AUC of 0.854 for LVI. Conclusion: The volumetric metabolic parameter MTV from preoperative FDG PET/CT is an independent predictor of tumor LVI in NSCLC. Clinical Impact: Further studies are warranted to assess the potential role of preoperative prediction of LVI using FDG PET/CT to help guide clinical decision making in NSCLC.

A Preliminary Study to Use SUVmax of FDG PET-CT as an Identifier of Lesion for Artificial Intelligence

Background: Diagnostic reports contribute not only to the particular patient, but also to constructing massive training dataset in the era of artificial intelligence (AI). The maximum standardized uptake value (SUVmax) is often described in daily diagnostic reports of [¹⁸F] fluorodeoxyglucose (FDG) positron emission tomography (PET) - computed tomography (CT). If SUVmax can be used as an identifier of lesion, that would greatly help AI interpret diagnostic reports. We aimed to clarify whether the lesion can be localized using SUVmax strings. Methods: The institutional review board approved this retrospective study. We investigated a total of 112 lesions from 30 FDG PET-CT images acquired with 3 different scanners. SUVmax was calculated from DICOM files based on the latest Quantitative Imaging Biomarkers Alliance (QIBA) publication. The voxels showing the given SUVmax were exhaustively searched in the whole-body images and counted. SUVmax was provided with 5 different degrees of precision: integer (e.g., 3), 1st decimal places (DP) (3.1), 2nd DP (3.14), 3rd DP (3.142), and 4th DP (3.1416). For instance, when SUVmax = 3.14 was given, the voxels with 3.135 ≤ SUVmax < 3.145 were extracted. We also evaluated whether local maximum restriction could improve the identifying performance, where only the voxels showing the highest intensity within some neighborhood were considered. We defined that "identical detection" was achieved when only single voxel satisfied the criterion. Results: A total of 112 lesions from 30 FDG PET-CT images were investigated. SUVmax ranged from 1.3 to 49.1 (median = 5.6). Generally, when larger and more precise SUVmax values were given, fewer voxels satisfied the criterion. The local maximum restriction was very effective. When SUVmax was determined to 4 decimal places (e.g., 3.1416) and the local maximum restriction was applied, identical detection was achieved in 33.3% (lesions with SUVmax < 2), 79.5% (2 ≤ SUVmax < 5), and 97.8% (5 ≤ SUVmax) of lesions. Conclusion: In this preliminary study, SUVmax of FDG PET-CT could be used as an identifier to localize the lesion if precise SUVmax is provided and local maximum restriction was applied, although the lesions showing SUVmax < 2 were difficult to identify. The proposed method may have potential to make use of diagnostic reports retrospectively for constructing training datasets for AI.

Early Reassessment of Total Metabolic Tumor Volume on FDG-PET/CT in Advanced Melanoma Patients Treated with Pembrolizumab Predicts Long-Term Outcome

PD-1 Immune checkpoint inhibitors, such as Pembrolizumab, can have a durable beneficial therapeutic effect in patients with advanced melanoma. However, not all patients will benefit equally from these therapies, and (potentially life-threatening) immune-related adverse events may occur. In this study, we investigate the value of early response assessment by FDG-PET/CT as a biomarker for predicting survival. We identified all patients with advanced melanoma who were treated with Pembrolizumab in our medical center and underwent a baseline and at least one follow-up FDG-PET/CT. The total metabolic tumor volume (TMTV) was calculated, and the evolution was compared to survival parameters. A total of 77 patients underwent a baseline and at least one follow-up FDG-PET/CT, 36 patients had follow-up imaging within 2–4 months, and 21 patients an FDG-PET/CT 5–6 months after baseline. When the TMTV evolution was categorized into two subgroups (stable/decrease versus increase), an association was found between stability or decrease in TMTV and better PFS and OS. A similar trend, however non-significant, was observed at 5–6 months. The evolution in TMTV as assessed by FDG-PET/CT 2–4 months after treatment initiation is associated with long-term outcomes in patients with advanced melanoma treated with Pembrolizumab.

Quantitative FDG PET Assessment for Oncology Therapy

Simple Summary

PET enables quantitative assessment of tumour biology in vivo. Accumulation of F-18 fluorodeoxyglucose (FDG) may reflect tumour metabolic activity. Quantitative assessment of FDG uptake can be applied for treatment monitoring. Numerous studies indicated biochemical change assessed by FDG-PET as a more sensitive marker than morphological change. Those with complete metabolic response after therapy may show better prognosis. Assessment of metabolic change may be performed using absolute FDG uptake or metabolic tumour volume. More recently, radiomics approaches have been applied to FDG PET. Texture analysis quantifies intratumoral heterogeneity in a voxel-by-voxel basis. Combined with various machine learning techniques, these new quantitative parameters hold a promise for assessing tissue characterization and predicting treatment effect, and could also be used for future prognosis of various tumours.

Abstract

Positron emission tomography (PET) has unique characteristics for quantitative assessment of tumour biology in vivo. Accumulation of F-18 fluorodeoxyglucose (FDG) may reflect tumour characteristics based on its metabolic activity. Quantitative assessment of FDG uptake can often be applied for treatment monitoring after chemotherapy or chemoradiotherapy. Numerous studies indicated biochemical change assessed by FDG PET as a more sensitive marker than morphological change estimated by CT or MRI. In addition, those with complete metabolic response after therapy may show better disease-free survival and overall survival than those with other responses. Assessment of metabolic change may be performed using absolute FDG uptake in the tumour (standardized uptake value: SUV). In addition, volumetric parameters such as metabolic tumour volume (MTV) have been introduced for quantitative assessment of FDG uptake in tumour. More recently, radiomics approaches that focus on image-based precision medicine have been applied to FDG PET, as well as other radiological imaging. Among these, texture analysis extracts intratumoral heterogeneity on a voxel-by-voxel basis. Combined with various machine learning techniques, these new quantitative parameters hold a promise for assessing tissue characterization and predicting treatment effect, and could also be used for future prognosis of various tumours, although multicentre clinical trials are needed before application in clinical settings.

Are lesion features reproducible between 18F-FDG PET/CT images when acquired on analog or digital PET/CT scanners?

OBJECTIVES

To compare lesion features extracted from ¹⁸F-FDG PET/CT images acquired on analog and digital scanners, on consecutive imaging data from the same subjects.

METHODS

Whole-body ¹⁸F-FDG PET/CT images from 55 oncological patients were acquired twice after a single ¹⁸F-FDG injection, with a digital and an analog PET/CT scanner, alternately. Twenty-nine subjects were examined first on the digital, and 26 first on the analog equipment. Image reconstruction was performed using manufacturer standard clinical protocols and protocols that fulfilled EARL1 specifications. Twenty-five features based on lesion standardized uptake value (SUV) and geometry were assessed. To compare these features, intraclass correlation coefficient (ICC), relative difference (RD), absolute value of RD (|RD|), and repeatability coefficient (RC) were used.

RESULTS

In total, 323 ¹⁸F-FDG avid lesions were identified. High agreement (ICC > 0.75) was obtained for most of the lesion features pulled out from both scanners' imaging data, especially when reconstruction protocols fulfilled EARL1 specifications. For EARL1 reconstruction images, the features frequently used in clinics, SUV_max, SUV_peak, SUV_mean, metabolic tumor volume, and total lesion glycolysis, reached an ICC of 0.92, 0.95, 0.87, 0.98, and 0.98, and a median RD (digital-analog) of 3%, 5%, 4%, - 3% and 1%, respectively. Using standard reconstruction protocols, the ICC were 0.84, 0.93, 0.80, 0.98, and 0.98, and the RD were 20%, 11%, 13%, - 7%, and 7%, respectively.

CONCLUSION

Under controlled acquisition and reconstruction parameters, most of the features studied can be used for research and clinical work. This is especially important for multicenter studies and patient follow-ups.

KEY POINTS

• Using manufacturer standard clinical reconstruction protocols, lesions SUV was significantly higher when using the digital scanner, especially the SUV_max that was approximately 20% higher. • High agreement was obtained for the majority of the lesion features when using reconstruction protocols that fulfilled EARL1 specifications. • Longitudinal patient studies can be performed interchangeably between digital and analog scanners when both fulfill EARL1 specifications.

Prediction of tumour grade and survival outcome using pre-treatment PET- and MRI-derived imaging features in patients with resectable pancreatic ductal adenocarcinoma

OBJECTIVES

To perform a correlation analysis between histopathology and imaging in patients with previously untreated pancreatic ductal adenocarcinoma (PDAC) and to determine the prognostic values of clinical, histological, and imaging parameters regarding overall survival (OS), disease-specific survival (DSS), and progression-free survival (PFS).

METHODS

This single-centre study prospectively included 61 patients (32 males; median age, 68.0 years [IQR, 63.0-75.0 years]) with histologically confirmed PDAC and following surgical resection who preoperatively underwent ¹⁸F-FDG PET/CT and DW-MRI. On whole lesions, we measured, using a 42% SUV_max threshold volume of interest (VOI), the following quantitative parameters: mean and maximum standardised uptake values (SUV_mean and SUV_max), total lesion glycolysis (TLG), metabolic tumour volume (MTV), mean and minimum apparent diffusion coefficient (ADC_mean and ADC_min), diffusion total volume (DTV), and MTV/ADC_min ratio. Spearman's correlation analysis was performed to assess relationships between these markers and histopathological findings from surgical specimens (stage; grade; resection quality; and vascular, perineural, and lymphatic invasion). Kaplan-Meier and Cox hazard ratio methods were used to evaluate the impacts of imaging parameters on OS (n = 41), DSS (n = 36), and PFS (n = 41).

RESULTS

Inverse correlations between ADC_min and SUV_max (rho = - 0.34; p = 0.0071), and between SUV_mean and ADC_mean (rho = - 0.29; p = 0.026) were identified. ADC_min was inversely correlated with tumour grade (rho = - 0.40; p = 0.0015). MTV was an independent predictive factor for OS and DSS, while DTV was an independent predictive factor for PFS.

CONCLUSION

In previously untreated PDAC, ADC and SUV values are correlated. Combining PET-MRI metrics may help predict PDAC grade and patients' survival.

KEY POINTS

• Minimum apparent diffusion coefficient derived from DW-MRI inversely correlates with tumour grade in pancreatic ductal adenocarcinoma. • In pancreatic ductal adenocarcinoma, metabolic tumour volume has been confirmed as a predictive factor for patients' overall survival and disease-specific survival. • Combining PET and MRI metrics may help predict grade and patients' survival in pancreatic ductal adenocarcinoma.

Influence on [18F]FDG uptake by cancer cells after anti-PD-1 therapy in an enforced-immune activated mouse tumor

Background

Anti-programmed cell death 1 (PD-1) antibody is an immune checkpoint inhibitor, and anti-PD-1 therapy improves the anti-tumor functions of T cells and affects tumor microenvironment. We previously reported that anti-PD-1 treatment affected tumor glycolysis by using 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) positron emission tomography (PET). That study showed that anti-PD-1 therapy in a mouse B16F10 melanoma model increased glucose metabolism in cancer cells at the point where anti-PD-1 therapy did not cause a significant inhibition of tumor growth. However, the B16F10 melanoma model is poorly immunogenic, so it is not clear how anti-PD-1 treatment affects glucose metabolism in highly immunogenic cancer models. In this study, we used a cyclic dinucleotide GMP-AMP (cGAMP)-injected B16F10 melanoma model to investigate the effect of anti-PD-1 therapy on [¹⁸F]FDG uptake in a highly immune activated tumor in mice.

Results

To compare the cGAMP-injected B16F10 model with the B16F10 model, experiments were performed as described in our previous manuscript. [¹⁸F]FDG-PET was measured before treatment and 7 days after the start of treatment. In this study, [¹⁸F]FDG uptake in tumors in the cGAMP/anti-PD-1 combination group was lower than that in the anti-PD-1 treatment group tumors on day 7, as shown by PET and ex vivo validation. Flow-cytometry was performed to assess immune cell populations and glucose metabolism. Anti-PD-1 and/or cGAMP treatment increased the infiltration level of immune cells into tumors. The cGAMP/anti-PD-1 combination group had significantly lower levels of GLUT1^high cells/hexokinase II^high cells in CD45⁻ cancer cells compared with tumors in the anti-PD-1 treated group. These results suggested that if immune responses in tumors are higher than a certain level, glucose uptake in cancer cells is reduced depending on that level. Such a change of glucose uptake might be caused by the difference in infiltration or activation level of immune cells between the anti-PD-1 treated group and the cGAMP/anti-PD-1 combination group.

Conclusions

[¹⁸F]FDG uptake in cancer cells after anti-PD-1 treatment might be affected by the tumor immune microenvironment including immune cell infiltration, composition, and activation status.

Prognostic significance of semi-quantitative FDG-PET parameters in stage I non-small cell lung cancer treated with carbon-ion radiotherapy

Purpose

Prognostic significance of volumetric ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computer tomography (PET/CT) parameters in carbon-ion radiotherapy (C-ion RT) treated stage I non-small cell lung cancer, and need of histology-wise separate cut-off values for risk stratification were assessed.

Methods

Thirty-nine patients (29 men and 10 women, 71.9 ± 8.3 years) who underwent FDG PET/CT examinations before C-ion RT were retrospectively evaluated. FDG-PET parameters: standardized uptake values (SUVmax, SUVpeak, and SUVmean), metabolic tumor volume (MTV), and total lesion glycolysis (TLG), and clinicopathological variables were assessed for prognosis using Cox proportional hazards regression analysis. Mann-Whitney test compared medians of significant parameters between adenocarcinoma (AC) and squamous cell carcinoma (SCC), and Kaplan-Meier curves were plotted for median-based low- and high-risk groups.

Results

Median follow-up period was 44.8 months. 1/2/3-year overall survival (OS), progression-free survival (PFS) and local control (LC) rates were 94.9/84.3/70.8, 82.1/69.2/58.4 and 97.3/85.7/82.3%. Multivariate analysis revealed age (hazard ratio, HR: 1.09; 95% confidence interval, CI: 1.0–1.19, p < 0.05) and MTV (HR 4.83, 95% CI 1.21–19.27, p < 0.03) predicted OS, and only MTV predicted PFS (HR 5.3, CI 1.32–21.35, p < 0.02) independently. Compared with AC, SCC had higher MTV (median, 6.625cm³ vs 0.2 cm³, p < 0.01). Single MTV cut-off based on overall cohort was insignificant in SCC for PFS (p > 0.02); separate cut-offs of MTV, 0.2 cm³ for AC (p < 0.03) and 6.625 cm³ for SCC (p < 0.05) were relevant.

Conclusion

Among all FDG PET/CT parameters, only MTV beared prognostic ability for stage I NSCLC treated with C-ion RT, and its histological variation may need consideration for risk-adapted therapeutic management.

The value of different 18F-FDG PET/CT baseline parameters in risk stratification of stage I surgical NSCLC patients

OBJECTIVE

Administration of postoperative chemotherapy to patients with completely resected stage I NSCLC is still a matter of debate. The aim of the present study was to evaluate the value of different baseline ¹⁸F-FDG PET parameters in identifying surgical stage I NSCLC patients who are at high risk of recurrence, and thus are indicated for further postoperative treatment.

METHODS

This is a retrospective study, which included 49 patients (28 males, 21 females) with the median age of 69 years (range 28-84), who had pathologically proven stage I NSCLC. All patients underwent ¹⁸F-FDG PET/CT at baseline followed by complete surgical resection of the tumor (R0). Baseline SUV_max, MTV and TLG were measured. Patients' follow-up records were retrospectively reviewed, and DFS (disease-free survival) was assessed. For each parameter, the most accurate cut-off value for the prediction of recurrence was calculated using the ROC curve analysis and the Youden index. DFS was evaluated for patients above and below the calculated cut-off value using the Kaplan-Meier method and the difference in survival between the two groups was estimated using the log-rank test.

RESULTS

Median observation time of the patients after surgery was 28.7 months (range 3.5-58.8 months). 9 patients developed recurrence. The calculated cut-off values for SUV_max, MTV and TLG were 6, 6.6 and 33.6, respectively. Using these cut-offs, the observed sensitivity for SUV_max, MTV and TLG for prediction of recurrence was 100%, 89% and 89%, respectively, while the observed specificity was 43%, 73% and 65%, respectively. The difference in survival between patients below and above the cut-off value was statistically significant in all three studied parameters. The highest AUC was observed for MTV (AUC = 0.825, p = 0.003), followed by TLG (AUC = 0.789, p = 0.007), and lastly SUV_max (AUC = 0.719, p = 0.041). ROC curve analysis showed that volumetric parameters had better predictive performance than SUV_max as regards recurrence.

CONCLUSION

PET-derived parameters at baseline were predictive of recurrence in stage I surgical NSCLC patients. Moreover, the metabolic volume of the tumor was the most significant parameter for this purpose among the studied indices.

Volume-based parameters on FDG PET may predict the proliferative potential of soft-tissue sarcomas

INTRODUCTION

Soft-tissue sarcomas (STS) are rare types of tumors that have variable levels of tumor differentiation. F-18 fluorodeoxyglucose positron emission tomography (FDG PET) has been established as an useful tool for STS patients, and the metabolic tumor volume (MTV) and total lesion glycolysis (TLG) are reported to be useful in various cancers. We compared the diagnostic value of four PET parameters (maximum standardized uptake value [SUVmax], SUVmean, MTV, and TLG) from two acquisition timings for predicting the expression of the pathological marker of cell proliferation Ki-67, based on pathological investigation.

MATERIALS AND METHODS

In this retrospective study, we investigated 20 patients (59 ± 19 years old, 18-87 years old) with pathologically confirmed STS who underwent FDG PET before surgical intervention. The patients fasted ≥ 6 h before the intravenous injection of FDG. The whole body was scanned twice; at an early phase (61.5 ± 2.6 min) and at a delayed phase (118.0 ± 2.1 min) post-injection. The SUVmax, SUVmean, MTV, and TLG of the primary lesion were measured with a tumor boundary determined by SUV ≥ 2.0. Ki-67 was measured using MIB-1 immunohistochemistry. We used Pearson's correlation coefficient to analyze the relationships between the PET parameters and Ki-67 expressions. The Kaplan-Meier analysis with the log-rank test was performed to compare overall survival between high-group and low-group at each of the four PET parameters and Ki-67 expression.

RESULTS

All four PET parameters at each phase showed significant correlations with Ki-67. Among them, the Pearson's correlation coefficient (r) was largest for TLG (r = 0.76 and 0.77 at the early and delayed phases, respectively), followed by MTV (0.70 and 0.72), SUVmax (r = 0.65 and 0.66), and SUVmean (r = 0.62 and r = 0.64). From early to delayed phases, the SUVmax and SUVmean both increased in all 20 patients, whereas the MTV and TLG increased in 13/20 (65%) and 16/20 (80%) patients, respectively. None of the %increases of the PET parameters were significantly correlated with Ki-67. The overall survival was shorter for high-SUVmax, high-SUVmean, high-TLG, and high-Ki-67 groups than the other groups, although the difference did not reach statistical significance.

CONCLUSION

The SUVmax, SUVmean, MTV, and TLG acquired at both 1 and 2 h after injection showed significant correlations with Ki-67. Among them, correlation coefficient with Ki-67 expression was highest for TLG, although the best parameter should be determined in a larger population. The delayed-phase FDG PET was equally useful as that of early-phase to predict tumor aggressiveness in STS.

Prognostic value of FDG PET/CT during radiotherapy in head and neck cancer patients

PURPOSE

To evaluate the prognostic value of 18F-fluorodeoxyglucose positron-emission tomography (FDG PET) with computed tomography (CT) before and during radiotherapy (RT) in patients with head and neck cancer.

METHODS

Twenty patients with primary head and neck squamous cell carcinoma were enrolled in this study, of whom 6 had oropharyngeal cancer, 10 had hypopharyngeal cancer, and 4 had laryngeal cancer. Fifteen patients received concurrent cisplatin and 2 received concurrent cetuximab chemotherapy. FDG PET/CT was performed before RT and in the 4th week of RT. The parameters of maximum standardized uptake value, metabolic tumor volume, and total lesion glycolysis (TLG) of the primary tumor were measured, and the prognostic significance of each was analyzed with the Cox proportional hazards model.

RESULTS

Higher TLG (&gt;19.0) on FDG PET/CT during RT was a poor prognostic factor for overall survival (OS) (p = 0.001) and progression-free survival (PFS) (p = 0.007). In the multivariate analysis, TLG during RT as a continuous variable was significantly associated with OS and PFS rate (p = 0.023 and p = 0.016, respectively). Tumor response worse than partial remission at 1 month after RT was another independent prognostic factor for PFS (p = 0.024). Conclusions: Higher TLG of the primary tumor on FDG PET/CT during RT was a poor prognostic factor for OS and PFS in patients with head and neck cancer.

Regional myocardial damage and active inflammation in patients with cardiac sarcoidosis detected by non-invasive multi-modal imaging

AIMS

Cardiac sarcoidosis (CS) can be diagnosed using ¹⁸F-FDG-PET/CT (PET), cardiovascular magnetic resonance (CMR), and ¹²³I-BMIPP/²⁰¹TlCl dual myocardial SPECT. This study aims to clarify the relationships among the three modalities with respect to CS.

METHODS AND RESULTS

We evaluated 16 patients (male n = 11; age 55 ± 13 years) with confirmed CS who underwent PET, CMR, and dual SPECT with gated SPECT before starting steroid therapy. The left ventricular myocardium was divided into 17 segments to obtain SUVmax for PET images, defect scores from 0 to 4 (0 normal; 4 absent), and mismatch scores for dual SPECT (BMDS, TLDS, and MS) images and late gadolinium enhancement (LGE) scores (0 none; 1 partly positive; 2 homogeneous) on CMR images. Summed BMDS, TLDS, and MS were 18.6 ± 12.6, 12.9 ± 10.9, and 5.7 ± 3.1, respectively. The segmental BMDS and TLDS scores became significantly higher as the LGE scores increased. The MS scores were significantly higher in areas of LGE with a score of 1 than 0 (both, p < 0.001), but did not significantly differ between areas with LGE scores of 1 and 2. The SUVmax was significantly higher in LGE areas with a score of 1 than 0 (p < 0.025), but did not significantly differ between those with scores of 1 or 2.

CONCLUSION

Regions with a higher SUVmax indicating active myocardial inflammation were mainly located in areas with LGE, where BMIPP and TL mismatches were evident in patients with CS.

Influence of volumetric 4'-[methyl-11C]-thiothymidine PET/CT parameters for prediction of the clinical outcome of head and neck cancer patients

OBJECTIVE

This prospective study compared the value of pretreatment 4'-[methyl-¹¹C]-thiothymidine (¹¹C-4DST) volumetric parameters and those of 2-deoxy-2-[18F] fluoro-D-glucose (¹⁸F-FDG) in predicting the clinical outcome in patients with head and neck squamous cell carcinoma (HNSCC).

METHODS

Fifty patients with HNSCC underwent ¹¹C-4DST PET/CT and ¹⁸F-FDG PET/CT prior to anticancer therapy. ¹⁸F-FDG metabolic tumor volume (¹⁸F-FDG MTV) and total lesion glycolysis (TLG) were calculated from ¹⁸F-FDG PET, and ¹¹C-4DST MTV and total lesion proliferation (TLP) were calculated from ¹¹C-4DST PET. All parameters were measured for the primary lesion and metastatic lymph nodes. Associations between clinical factors and PET/CT parameters and prognostic value were analyzed.

RESULTS

Receiver-operating characteristic analysis revealed that MTV, TLG, and TLP acquired from the primary lesion and metastatic lymph nodes were good parameters for predicting disease relapse and death. The area under the curves (AUCs) ranged from 0.63 to 0.71 for ¹⁸F-FDG PET/CT parameters. The AUCs of ¹¹C-4DST PET/CT parameters were larger than those of ¹⁸F-FDG (range 0.72-0.81). Univariate analysis revealed that individuals with tumors showing a high value for any PET/CT parameter were at a significantly increased risk of relapse. Upon multivariate analysis, ¹⁸F-FDG MTV, ¹¹C-4DST MTV and ¹¹C-4DST TLP were significant independent factors for relapse-free survival (P = 0.04, P = 0.0001 and P = 0.0005, respectively).

CONCLUSION

Pretreatment ¹¹C-4DST PET/CT volume-based parameters can provide important prognostic information about patients with HNSCC.