What and how should we measure in paediatric oncology FDG-PET/CT? Comparison of commonly used SUV metrics for differentiation between paediatric tumours

Predictive value of 2-deoxy-2-fluorine-18-fluoro-D-glucose positron emission tomography/computed tomography parameters for MYCN amplification in high-risk neuroblastoma

OBJECTIVES

To investigate the predictive value of 2-deoxy-2-fluorine-18-fluoro-D-glucose positron emission tomography/computed tomography (18F-FDG PET/CT) parameters for MYCN amplification in high-risk neuroblastoma (HR-NB).

MATERIALS AND METHODS

A retrospective analysis was performed by reviewing 68 HR-NB patients who underwent MYCN testing and 18F-FDG PET/CT imaging at our hospital between January 2018 and December 2019. Based on the results of MYCN testing, patients were categorized into either the MYCN-amplified (MNA) or MYCN non-amplified (MYCN-NA) group. The 18F-FDG PET/CT parameters, including maximum standardized uptake value (SUVmax), mean standardized uptake value (SUVmean), peak standardized uptake value (SUVpeak), tumor metabolic volume (MTV), total lesion glycolysis (TLG), coefficient of variation (COV), and areas under the curve of cumulative SUV-volume histogram index (AUC-CSH index) were evaluated. Independent predictors were identified through univariate and multivariate logistic regression analyses, and their diagnostic performance was evaluated using the receiver-operating characteristic (ROC) curve.

RESULTS

Univariate logistic regression analysis revealed that SUVpeak was significantly associated with MYCN amplification. Multivariate logistic regression analysis showed that SUVpeak was an independent predictor of MYCN amplification in HR-NB [Odds ratio (OR) = 0.673, 95 % confidence interval (95 % CI): 0.494-0.917, P = 0.012]. ROC curve analysis demonstrated that the predictive model including SUVpeak had higher diagnostic performance [area under the curve (AUC): 0.790, 95 % CI: 0.677-0.881, sensitivity: 0.861, specificity: 0.591, positive predictive value (PPV): 0.820, negative predictive value (NPV): 0.722] compared to using SUVpeak alone (AUC: 0.640, 95 % CI: 0.514-0.752, sensitivity: 0.630, specificity: 0.682, PPV: 0.806, NPV: 0.469).

CONCLUSION

SUVpeak can predict the MYCN amplification in HR-NB patients. The predictive model constructed by combining SUVpeak and age can distinguish MYCN status in HR-NB non-invasively with superior efficacy compared to using SUVpeak alone.

Are Semiquantitative Methods Superior to Deauville Scoring in the Monitoring Therapy Response for Pediatric Hodgkin Lymphoma?

Tailoring treatment in patients with Hodgkin lymphoma (HL) is paramount to maximize outcomes while avoiding unnecessary toxicity. We aimed to compare the performance of SUVmax reduction (ΔSUVmax%) and the PET ratio (rPET) versus the Deauville score (DS) for assessing the chemotherapy response in pediatric HL patients undergoing 18F-FDG PET-CT. Fifty-two patients with biopsy-proven HL (aged 8-16 years) were enrolled at baseline, interim (after the second or third chemotherapy round) and post-therapy (on completion of first-line chemotherapy). Interim and post-therapy DS, ΔSUVmax% and rPET were compared as response predictors. Patients were classified as responders or non-responders based on a 24-month clinical follow-up. Interim DS showed a sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and diagnostic accuracy of 100%, 80.4%, 100%, 40% and 82.7%, respectively, in predicting the therapy response. Post-therapy DS showed a sensitivity, specificity, PPV, NPV and accuracy of 66.7%, 97.8%, 95.7%, 80% and 94.2%, repsectively. Interim ΔSUVmax% showed a sensitivity, specificity, PPV, NPV and accuracy of 83.3%, 82.6%, 97.4%, 38.5% and 82.7%, respectively, with a 56.3% cutoff. Post-therapy ΔSUVmax% showed a sensitivity, specificity, PPV, NPV and accuracy of 83.3%, 84.8%, 97.5%, 41.7% and 84.6%, respectively, with a 76.8% cutoff. Compared to ΔSUVmax%, DS showed a significantly higher sensitivity, specificity (p < 0.05) and NPV (p < 0.01). The sensitivity, specificity, PPV, NPV and accuracy of rPET in predicting the therapy response at 24 months were 76.1%, 100%, 100%, 35.3% and 78.8%, respectively, with a cut-off of 1.31. DS and rPET showed comparable predictive performance (p > 0.58). In conclusion, DS is an easier method with better performance than ΔSUVmax% and rPET in predicting the chemotherapy response in pediatric HL patients.

Evaluation of physiological Waldeyer's ring, mediastinal blood pool, thymic, bone marrow, splenic and hepatic activity with 18F-FDG PET/CT: exploration of normal range among pediatric patients

INTRODUCTION

While ¹⁸F-FDG PET/CT pediatrics applications have increased in number and indications, few studies have addressed normal maximum standardized uptake values (SUV_max) of referral organs in children. The purpose of this study is to assess these in a cohort of pediatric patients.

MATERIAL AND METHODS

285 ¹⁸F-FDG PET/CT scans in 229 patients were reviewed. SUV_max were assessed for mediastinal blood pool (MBP), thymus (T), liver (L), spleen (S), bone marrow (BM) and Waldeyer's Ring (Wald). L/MBP and S/L ratios were calculated. Same day complete blood counts (CBC) were available for 132 studies and compared to BM and S. Means, standard deviations and correlation coefficients with age, weight and body surface area (BSA) were calculated.

RESULTS

Weak correlation with age, weight or BSA was found for Wald. Strong correlations with weight/BSA more than with age were demonstrated for MBP, L and BM and moderate for S and T. After initial decrease between age 0 and 2, thymic activity peaked at age 11 years then involuted. No correlation was found between CBC ad BM or S. In 28 studies, L was less or equal to MBP. In 74 S was superior to L.

CONCLUSIONS

Referral organs ¹⁸F-FDG uptake varies in children more in relation with weight and BSA than with age for key referral organs, such as L, S and MBP. In a significant number of studies, L activity may impede evaluation of treatment response in comparison with MBP or inflammation/infection evaluation in comparison with S.

Clinical Perspectives for 18F-FDG PET Imaging in Pediatric Oncology: Μetabolic Tumor Volume and Radiomics

Pediatric cancer, although rare, requires the most optimized treatment approach to obtain high survival rates and minimize serious long-term side effects in early adulthood. 18F-FDG PET/CT is most helpful and widely used in staging, recurrence detection, and response assessment in pediatric oncology. The well-known 18F-FDG PET metabolic indices of metabolic tumor volume (MTV) and tumor lesion glycolysis (TLG) have already revealed an independent significant prognostic value for survival in oncologic patients, although the corresponding cut-off values remain study-dependent and not validated for use in clinical practice. Advanced tumor “radiomic” analysis sheds new light into these indices. Numerous patterns of texture 18F-FDG uptake features can be extracted from segmented PET tumor images due to new powerful computational systems supporting complex “deep learning” algorithms. This high number of “quantitative” tumor imaging data, although not decrypted in their majority and once standardized for the different imaging systems and segmentation methods, could be used for the development of new “clinical” models for specific cancer types and, more interestingly, for specific age groups. In addition, data from novel techniques of tumor genome analysis could reveal new genes as biomarkers for prognosis and/or targeted therapies in childhood malignancies. Therefore, this ever-growing information of “radiogenomics”, in which the underlying tumor “genetic profile” could be expressed in the tumor-imaging signature of “radiomics”, possibly represents the next model for precision medicine in pediatric cancer management. This paper reviews 18F-FDG PET image segmentation methods as applied to pediatric sarcomas and lymphomas and summarizes reported findings on the values of metabolic and radiomic features in the assessment of these pediatric tumors.

Image-Guided Biopsy for Relapsed Neuroblastoma: Focus on Safety, Adequacy for Genetic Sequencing, and Correlation of Tumor Cell Percent With Quantitative Lesion MIBG Uptake

PURPOSE

Many novel therapies for relapsed and refractory neuroblastoma require tumor tissue for genomic sequencing. We analyze our experience with image-guided biopsy in these patients, focusing on safety, yield, adequacy for next-generation sequencing (NGS), and correlation of tumor cell percent (TC%) with quantitative uptake on ¹²³I-meta-iodobenzylguanidine (MIBG) single-photon emission computed tomography with computed tomography (SPECT/CT).

MATERIALS AND METHODS

An 11-year retrospective review of image-guided biopsy on 66 patients (30 female), with a median age of 8.7 years (range, 0.9-49 years), who underwent 95 biopsies (55 bone and 40 soft tissue) of relapsed or refractory neuroblastoma lesions was performed.

RESULTS

There were seven minor complications (7%) and one major complication (1%). Neuroblastoma was detected in 88% of MIBG- or fluorodeoxyglucose-avid foci. The overall NGS adequacy was 69% (64% in bone and 74% in soft tissue, P = .37). NGS adequacy within neuroblastoma-positive biopsies was 88% (82% bone and 96% soft tissue, P = .11). NGS-adequate biopsies had a greater mean TC% than inadequates (51% v 18%, P = .03). NGS-adequate biopsies had a higher mean number of needle passes (7.5 v 3.4, P = .0002). The mean tissue volume from NGS-adequate soft-tissue lesions was 0.16 cm³ ± 0.12. Lesion:liver and lesion:psoas MIBG uptake ratios correlated with TC% (r = 0.74, r = 0.72, and n = 14). Mean TC% in NGS-adequate samples was 51%, corresponding to a lesion:liver ratio of 2.9 and a lesion:psoas ratio of 9.0. Thirty percent of biopsies showed an actionable ALK mutation or other therapeutically relevant variant.

CONCLUSION

Image-guided biopsy for relapsed or refractory neuroblastoma was safe and likely to provide NGS data to guide therapy decisions. A lesion:liver MIBG uptake ratio of ≥ 3 or a lesion:psoas ratio of > 9 was associated with a TC% sufficient to deliver NGS results.

Positron Emission Tomography for Response Evaluation in Microenvironment-Targeted Anti-Cancer Therapy

Therapeutic response is evaluated using the diameter of tumors and quantitative parameters of 2-[¹⁸F] fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET). Tumor response to molecular-targeted drugs and immune checkpoint inhibitors is different from conventional chemotherapy in terms of temporal metabolic alteration and morphological change after the therapy. Cancer stem cells, immunologically competent cells, and metabolism of cancer are considered targets of novel therapy. Accumulation of FDG reflects the glucose metabolism of cancer cells as well as immune cells in the tumor microenvironment, which differs among patients according to the individual immune function; however, FDG-PET could evaluate the viability of the tumor as a whole. On the other hand, specific imaging and cell tracking of cancer cell or immunological cell subsets does not elucidate tumor response in a complexed interaction in the tumor microenvironment. Considering tumor heterogeneity and individual variation in therapeutic response, a radiomics approach with quantitative features of multimodal images and deep learning algorithm with reference to pathologic and genetic data has the potential to improve response assessment for emerging cancer therapy.