[(18)F]FDG in childhood lymphoma: clinical utility and impact on management

Evaluation of pediatric malignancies using total-body PET/CT with half-dose [18F]-FDG

PURPOSE

To explore the impact of a true half dose of [¹⁸F]-FDG on image quality in pediatric oncological patients undergoing total-body PET/CT and investigate short acquisition times with half-dose injected activity.

METHODS

One hundred pediatric oncological patients who underwent total-body PET/CT using the uEXPLORER scanner after receiving a true half dose of [¹⁸F]-FDG (1.85 MBq/kg) were retrospectively enrolled. The PET images were first reconstructed using complete 600-s data and then split into 300-s, 180-s, 60-s, 40-s, and 20-s duration groups (G600 to G20). The subjective analysis was performed using 5-point Likert scales. Objective quantitative metrics included the maximum standard uptake value (SUV_max), SUV_mean, standard deviation (SD), signal-to-noise ratio (SNR), and SNR_norm of the background. The variabilities in lesion SUV_mean, SUV_max, and tumor-to-background ratio (TBR) were also calculated.

RESULTS

The overall image quality scores in the G600, G300, G180, and G60 groups were 4.9 ± 0.2, 4.9 ± 0.3, 4.4 ± 0.5, and 3.5 ± 0.5 points, respectively. All the lesions identified in the half-dose images were localized in the G60 images, while 56% of the lesions could be clearly identified in the G20 images. With reduced acquisition time, the SUV_max and SD of the backgrounds were gradually increased, while the TBR values showed no statistically significant differences among the groups (all p > 0.1). Using the half-dose images as a reference, the variability in the lesion SUV_max gradually increased from the G180 to G20 images, while the lesion SUV_mean remained stable across all age groups. SNR_norm was highly negatively correlated with age.

CONCLUSION

Total-body PET/CT with a half dose of [¹⁸F]-FDG (1.85 MBq/kg, estimated whole-body effective dose: 1.76-2.57 mSv) achieved good performance in pediatric patients, with sufficient image quality and good lesion conspicuity. Sufficient image quality and lesion conspicuity could be maintained at a fast scanning time of 60 s with half-dose activity.

Validation of Deep Learning-based Augmentation for Reduced 18F-FDG Dose for PET/MRI in Children and Young Adults with Lymphoma

Purpose

To investigate if a deep learning convolutional neural network (CNN) could enable low-dose fluorine 18 (¹⁸F) fluorodeoxyglucose (FDG) PET/MRI for correct treatment response assessment of children and young adults with lymphoma.

Materials and Methods

In this secondary analysis of prospectively collected data (ClinicalTrials.gov identifier: NCT01542879), 20 patients with lymphoma (mean age, 16.4 years ± 6.4 [standard deviation]) underwent ¹⁸F-FDG PET/MRI between July 2015 and August 2019 at baseline and after induction chemotherapy. Full-dose ¹⁸F-FDG PET data (3 MBq/kg) were simulated to lower ¹⁸F-FDG doses based on the percentage of coincidence events (representing simulated 75%, 50%, 25%, 12.5%, and 6.25% ¹⁸F-FDG dose [hereafter referred to as 75%_Sim, 50%_Sim, 25%_Sim, 12.5%_Sim, and 6.25%_Sim, respectively]). A U.S. Food and Drug Administration-approved CNN was used to augment input simulated low-dose scans to full-dose scans. For each follow-up scan after induction chemotherapy, the standardized uptake value (SUV) response score was calculated as the maximum SUV (SUV_max) of the tumor normalized to the mean liver SUV; tumor response was classified as adequate or inadequate. Sensitivity and specificity in the detection of correct response status were computed using full-dose PET as the reference standard.

Results

With decreasing simulated radiotracer doses, tumor SUV_max increased. A dose below 75%_Sim of the full dose led to erroneous upstaging of adequate responders to inadequate responders (43% [six of 14 patients] for 75%_Sim; 93% [13 of 14 patients] for 50%_Sim; and 100% [14 of 14 patients] below 50%_Sim; P < .05 for all). CNN-enhanced low-dose PET/MRI scans at 75%_Sim and 50%_Sim enabled correct response assessments for all patients. Use of the CNN augmentation for assessing adequate and inadequate responses resulted in identical sensitivities (100%) and specificities (100%) between the assessment of 100% full-dose PET, augmented 75%_Sim, and augmented 50%_Sim images.

Conclusion

CNN enhancement of PET/MRI scans may enable 50% ¹⁸F-FDG dose reduction with correct treatment response assessment of children and young adults with lymphoma.Keywords: Pediatrics, PET/MRI, Computer Applications Detection/Diagnosis, Lymphoma, Tumor Response, Whole-Body Imaging, Technology AssessmentClinical trial registration no: NCT01542879 Supplemental material is available for this article. © RSNA, 2021.

RS, Janarthinakani M, Prasad K, Patil C, Anoop P, Reddy N, Anumula SK, Roopa SP, Golamari KR, Danthala M, Malipatil B, Rangarajan B, Udupa KS, Nandennavar M, Niraimathi K. Role of Interim PET Scan after 2 Cycles of ABVD in Pediatric Hodgkin Lymphoma: Retrospective Multicenter Study from South India

Introduction Most Indian centers use Adriamycin/Bleomycin/Vinblastine/Dacarba-zine (ABVD) chemotherapy for pediatric Hodgkin lymphoma (pHL). To reduce the late toxicity, robust predictive markers are needed to risk stratify pHL patients, thereby limiting the number of chemotherapy cycles and omitting radiation for low-risk and intensifying treatment for high-risk children.

Objective This study was conducted to analyze the outcome of pHL patients treated with ABVD and various factors predicting the outcome.

Materials and Methods This retrospective study analyzed the outcome of 113 consecutive pHL children treated with ABVD chemotherapy from 11 tertiary care centers in South India from 2009 to 2019.

Results The median duration of follow-up was 2.73 years. The median age was 13 years. B symptoms are seen in 50.5% patients, bulky disease in 23%, and stage IV in 28.3%. Of 113 pHL, 69% had a positron emission tomography (PET) and 31% had computed tomography (CT)-based staging. Stage IV (37.1%) and extranodal involvement (31.2%) were seen more often with PET than with CT staging (8.5 and 2.8%, respectively). Among 64 patients with interim PET scan after two cycles (iPET2), 20.3% did not achieve complete remission (CR) and no factors were significantly associated. The 4-year event-free survival (EFS) rate of the entire cohort was 86%. The 4-year EFS rate was 93% for patients with CR in iPET2 and 52% for patients not achieving CR. The only independent predictor of low EFS was iPET2 response (p < 0.05).

Conclusion Our study confirms the prognostic role of PET scan staging and response assessment. Not achieving CR on the iPET2 scan indicates poor prognosis and warrants clinical trial enrollment for a better outcome.

Roles of F-18-Fluoro-2-Deoxy-Glucose PET/Computed Tomography Scans in the Management of Post-Transplant Lymphoproliferative Disease in Pediatric Patient

Post-transplant lymphoproliferative disease is a well-known complication in transplant recipients. Evaluating the extent and stage of disease is important for management and follow-up. As a combination of anatomic and functional imaging, PET/CT is a sensitive and specific tool to stage and detect occult disease compared with conventional imaging. PET/CT also has a role in monitoring treatment response. Although PET/CT has been shown to be potentially useful in adults, evidence in children is insufficient. This review provides an overview of the use of PET/CT in post-transplant lymphoproliferative disease, especially in pediatric patients.

2-deoxy-2[F-18] fluoro-D-glucose positron emission tomography Deauville scale and core-needle biopsy to determine successful management after six doxorubicin, bleomycin, vinblastine and dacarbazine cycles in advanced-stage Hodgkin lymphoma

BACKGROUND

The clinical impact of the positivity of the Deauville scale (DS) of positron emission tomography (PET) performed at the end of doxorubicin, bleomycin, vinblastine and dacarbazine (ABVD) in patients with advanced Hodgkin lymphoma (HL), in terms of providing rationale to shift poor responders onto a more intensive regimen, remain to be validated by histopathology.

PATIENTS AND METHODS

This prospective trial involved patients with stage IIB/IV HL who after six ABVD cycles underwent PET (PET6) and core-needle cutting biopsy (CNCB) of 2-deoxy-2[F-18] fluoro-d-glucose (FDG)-avid lymph nodes. Patients received high-dose chemotherapy/autologous haematopoietic stem cell rescue (HDCT/AHSCR) if CNCB was positive for HL, alternatively, if CNCB or PET was negative, received observation or consolidation radiotherapy (cRT) on residual nodal masses, as initially planned. The end-point was 5-year progression-free survival (PFS).

RESULTS

In all, 43 of the 169 (25%) evaluable patients were PET6 positive (DS 4, 32; DS 5, 11). Among them, histology showed malignancy (HL) in 100% of DS 5 scores and in 12.5% of DS 4 scores. Fifteen patients with positive biopsy received HDCT/AHSCR, whereas 28 patients with negative biopsy, as well as 126 patients with negative PET6, continued the original plan (cRT, 78 patients; observation, 76 patients). The 5-year PFS in the negative PET6 group, negative biopsy group and positive biopsy group was 95.4%, 100% and 52.5%, respectively.

CONCLUSION

DS positivity of end-of-ABVD PET in advanced HL carried a certain number of CNCB-proven non-malignant FDG-uptakes. The DS 4 scores which were found to have negative histology appeared to benefit from continuing the original non-intensive therapeutic plane as indicated by the successful outcome in more than 95% of them by obtaining similar 5-year PFS to the PET6-negative group. By contrast, the DS 5 score had consistently positive histology and was associated with unsuccessful conventional therapy, promptly requiring treatment intensification or innovative therapeutic approaches.

[Rebound (reactive) thymic hyperplasia after chemotherapy in children with lymphoma]

INTRODUCTION

Thymic regrowth after chemotherapy treatment has been reported in children with lymphoma, and in order to avoid misdiagnosing these cases as relapses, physicians should become familiar with rebound (reactive) thymic hyperplasia (RTH) and remain aware of its possible occurrence. We aimed to estimate the prevalence of RTH in children with lymphoma after completion of chemotherapy and to evaluate the clinical characteristics, outcomes, and the findings of computed tomography (CT) and gallium-67 (GA-67) scans in these patients.

PATIENTS AND METHODS

We conducted a retrospective cross-sectional study by reviewing the health records of children with a lymphoma diagnosis managed at an outpatient paediatric oncology clinic in Jeddah, Saudi Arabia.

RESULTS

Rebound thymic hyperplasia was detected in 51.9% of the lymphoma patients (14/27). It developed a median of 2.5 months after completion of chemotherapy (range, 2.0-4.25 months). Patients with RTH had significantly shorter treatment durations, and we found no significant differences between patients with and without RTH in sex, age at diagnosis, type of lymphoma or type of treatment received. All patients with RTH were asymptomatic, and routine laboratory tests did not detect any abnormalities in them. The findings of CT and GA-67 scans were highly suggestive of RTH. None of the patients with RTH had a recurrence, and RTH resolved spontaneously within a median of 6 months (range, 4.0-11.0).

CONCLUSION

RTH was detected in ∼50% of children with lymphoma after completion of chemotherapy. A clinical evaluation and laboratory tests combined with imaging by CT and GA-67 can help identify RTH and rule out other lesions elsewhere.

Preliminary experience on the use of PET/CT in the management of pediatric post-transplant lymphoproliferative disorder

INTRODUCTION

Post-transplant lymphoproliferative disorder (PTLD) is a well-known complication following prolonged immunosuppression. Contrary to other lymphomas, there is no standardized imaging approach to assess PTLD either at staging or for response to therapy. Positron emission tomography/computed tomography (PET/CT) is an imaging modality that has proven to be useful in lymphoma. However, there is still limited data concerning its use in pediatric PTLD. Our study evaluates the use of PET/CT in pediatric PTLD at our institution.

METHODS

To assess the role of PET/CT in pediatric PTLD, we reviewed the pediatric patients with PTLD who had undergone PET/CT at our institution between 2000 and 2016.

RESULTS

Nine patients were identified. Six had PET/CT at diagnosis. All lesions seen on CT were identified with PET/CT. Fourteen PET/CTs were done during treatment. Eight PET/CTs were negative, including three where CT showed areas of uncertain significance. In these cases, PET/CT helped us to stop treatment and the patients remain in remission after a long follow-up (mean 74.3 months; range 12.4-180.9 months). PET/CT revealed additional disease in two cases, therefore treatment was intensified. Six biopsies and close follow-up was done to confirm PET/CT results. In one case, PET/CT did not identify central nervous system involvement demonstrated on magnetic resonance imaging.

CONCLUSION

PET/CT may have an important role in the staging and follow-up of pediatric PTLD. In our cohort, PET/CT was helpful in staging and assessing treatment response and in clarifying equivocal findings on other imaging modalities.

Nuclear Medicine in Pediatric and Adolescent Tumors

Nuclear medicine has an important role in the management of many cancers in pediatric age group with multiple imaging modalities and radiopharmaceuticals targeting various biological uptake mechanisms. 18-Flourodeoxyglucose is the radiotracer of choice especially in patients with sarcoma and lymphoma. (18)FDG-PET, for sarcoma and lymphomas, is proved to be superior to conventional imaging in staging and therapy response. Although studies are limited in pediatric population, (18)FDG-PET/CT has found its way through international guidelines. Limitations and strengths of PET imaging must be noticed before adapting PET imaging in clinical protocols. Established new response criteria using multiple parameters derived from (18)FDG-PET would increase the accuracy and repeatability of response evaluation. Current data suggest that I-123 metaiodobenzylguanidine (MIBG) remains the tracer of choice in the evaluation of neuroblastoma (NB) because of its high sensitivity, specificity, diagnostic accuracy, and prognostic value. It is valuable in determining the response to therapy, surveillance for disease recurrence, and in selecting patients for I-131 therapy. SPECT/CT improves the diagnostic accuracy and the interpretation confidence of MIBG scans. (18)FDG-PET/CT is an important complementary to MIBG imaging despite its lack of specificity to NB. It is valuable in cases of negative or inconclusive MIBG scans and when MIBG findings underestimate the disease status as determined from clinical and radiological findings. F-18 DOPA is promising tracer that reflects catecholamine metabolism and is both sensitive and specific. F-18 DOPA scintigraphy provides the advantages of PET/CT imaging with early and short imaging times, high spatial resolution, inherent morphologic correlation with CT, and quantitation. Regulatory and production issues currently limit the tracer's availability. PET/CT with Ga-68 DOTA appears to be useful in NB imaging and may have a unique role in selecting patients for peptide receptor radionuclide therapy with somatostatin analogues. C-11 hydroxyephedrine PET/CT is a specific PET tracer for NB, but the C-11 label that requires an on-site cyclotron production and the high physiologic uptake in the liver and kidneys limit its use. I-124 MIBG is useful for I-131 MIBG pretherapeutic dosimetry planning. Its use for diagnostic imaging as well as the use of F-18 labeled MIBG analogues is currently experimental. PET/MR imaging is emerging and is likely to become an important tool in the evaluation. It provides metabolic and superior morphological data in one imaging session, expediting the diagnosis and lowering the radiation exposure. Radioactive iodines not only detect residual tissue and metastatic disease but also are used in the treatment of differentiated thyroid cancer. However, these are not well documented in pediatric age group like adult patients. Use of radioactivity in pediatric population is very important and strictly controlled because of the possibility of secondary malignities; therefore, management of oncological cases requires detailed literature knowledge. This article aims to review the literature on the use of radionuclide imaging and therapy in pediatric population with thyroid cancer, sarcomas, lymphoma, and NB.

Current Role of FDG-PET in Pediatric Hodgkin's Lymphoma

Hodgkin's lymphoma is one of the most curable pediatric cancers with long-term survival rates exceeding 90% following intensive treatment. Collaborative group studies worldwide aim on reduction or elimination of radiotherapy to avoid potentially life-limiting late effects especially second cancers and cardiovascular diseases. Large prospective trials have integrated early response FDG-PET scans to identify adequate responders to chemotherapy in whom radiotherapy may safely be omitted. The criteria for interpretation of early response PET have changed during the past years and will be further refined based on trial results. FDG-PET is also systematically used to assess initial disease involvement of pediatric Hodgkin's lymphoma and could replace bone marrow biopsy. This article summarizes the role of FDG-PET in staging and response assessment focusing on large pediatric trials, the criteria for PET interpretation and pitfalls.

How PET/MR Can Add Value For Children With Cancer

PURPOSE

To review how PET/MR technology could add value for pediatric cancer patients.

RECENT FINDINGS

Since many primary tumors in children are evaluated with MRI and metastases are detected with PET/CT, integrated PET/MR can be a time-efficient and convenient solution for pediatric cancer staging. 18F-FDG PET/MR can assess primary tumors and the whole body in one imaging session, avoid repetitive anesthesia and reduce radiation exposure compared to 18F-FDG PET/CT. This article lists 10 action points, which might improve the clinical value of PET/MR for children with cancer. However, even if PET/MR proves valuable, it cannot enter mainstream applications if it is not accessible to the majority of pediatric cancer patients. Therefore, innovations are needed to make PET/MR scanners affordable and increase patient throughput.

SUMMARY

PET/MR offers opportunities for more efficient, accurate and safe diagnoses of pediatric cancer patients. The impact on patient management and outcomes has to be substantiated by large-scale prospective clinical trials.

Posttreatment PET/CT Rather Than Interim PET/CT Using Deauville Criteria Predicts Outcome in Pediatric Hodgkin Lymphoma: A Prospective Study Comparing PET/CT with Conventional Imaging

Data about the significance of ¹⁸F-FDG PET at interim assessment and end of treatment in pediatric Hodgkin lymphoma (HL) are limited. Methods: Patients (≤18 y) with HL were prospectively evaluated with contrast-enhanced CT (CECT) and PET combined with low-dose CT (PET/CT) at baseline, after 2 cycles of chemotherapy, and after completion of treatment. Revised International Working Group (RIW) criteria and Deauville 5 point-scale for response assessment by PET/CT were used. All patients received doxorubicin (Adriamycin), bleomycin, vinblastine, dacarbazine chemotherapy along with involved-field radiotherapy (25 Gy) for early stage (IA, IB, and IIA) and advanced stage (IIB-IV) with bulky disease. Results: Of the 57 enrolled patients, median follow-up was 81.6 mo (range, 11-97.5 mo). Treatment decisions were based on CECT. At baseline, PET/CT versus CECT identified 67 more disease sites; 23 patients (40.3%) were upstaged and of them in 9 patients (39%) upstaging would have affected treatment decision; notably none of these patients relapsed. The specificity of interim PET/CT based on RIW criteria (61.5%) and Deauville criteria (91.4%) for predicting relapse was higher than CECT (40.3%) (P = 0.03 and P < 0.0001, respectively). Event-free survival based on interim PET/CT (RIW) response was 93.3 ± 4.1 versus 89.6 ± 3.8 (positive vs. negative scan, respectively; P = 0.44). The specificity of posttreatment PET/CT (Deauville) was 95.7% versus 76.4% by CECT (P = 0.006). Posttreatment PET/CT (Deauville) showed significantly inferior overall survival in patients with positive scan versus negative scan results (66.4 ± 22.5 vs. 94.5 ± 2.0, P = 0.029). Conclusion: Interim PET/CT has better specificity, and use of Deauville criteria further improves it. Escalation of therapy based on interim PET in pediatric HL needs further conclusive evidence to justify its use. Posttreatment PET/CT (Deauville) predicts overall survival and has better specificity in comparison to conventional imaging.

Proportion of false-positive lesions at interim and end-of-treatment FDG-PET in lymphoma as determined by histology: Systematic review and meta-analysis

PURPOSE

To systematically review and meta-analyze the proportion of false-positive lesions at interim and end-of-treatment ¹⁸F-fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) in lymphoma using biopsy as reference standard.

MATERIALS AND METHODS

Medline was searched for original studies. Methodological quality of included studies was evaluated, and results were meta-analytically summarized using random effects (in case of interstudy heterogeneity [I²≤50%]) or fixed effects (in case of no interstudy heterogeneity [I²>50%]).

RESULTS

Eleven studies, comprising 139 patients who underwent biopsy of an FDG-avid lesion during or after completion of antilymphoma treatment, were included. Overall methodological quality was moderate. The proportion of false-positive results among all biopsied FDG-avid lesions at PET performed during of after completion of treatment ranged between 7.7% and 90.5% (the vast majority was due to inflammatory changes), with a weighted summary proportion (random effects, I²=75.7%) of 55.7% (95% confidence interval [CI]: 32.6-76.6%). There were no available studies on interim FDG-PET in Hodgkin lymphoma. The pooled summary false-positive proportions were 83.0% (95% CI: 72.0%-90.2%) for interim FDG-PET in non-Hodgkin lymphoma (fixed effects, I²=27.7%), 23.1% (95% CI: 4.7%-64.5%) for end-of-treatment FDG-PET in Hodgkin lymphoma (random effects; I²=67.1%), and 31.5% (95% CI: 3.9%-83.9%) for end-of-treatment FDG-PET in non-Hodgkin lymphoma (random effects, I²=68.3%).

CONCLUSION

Both interim and end-of-treatment FDG-PET scans in patients with lymphoma suffer from a very high number of false-positive FDG-avid lesions. This finding, in combination with the previously reported high number of false-negative FGD-PET scans for residual disease detection, suggests that the role of interim and end-of-treatment FDG-PET should be reconsidered.

Imaging Evaluation of Mediastinal Masses in Children and Adults: Practical Diagnostic Approach Based on A New Classification System

A compartmental approach to the diagnosis of the mediastinal masses in children and adults has been widely used to facilitate the diagnosis and planning of diagnostic interventions and surgical treatment for many years. Recently, a new computed tomography-based mediastinal division scheme, approved by the International Thymic Malignancy Interest Group, has received considerable attention as a potential new standard. In this review article, this new computed tomography-based mediastinal division scheme is described and illustrated. In addition, currently used imaging modalities and techniques, practical imaging algorithm of evaluating mediastinal masses, and characteristic imaging findings of various mediastinal masses that occur in children and adults are discussed. Such up-to-date knowledge has the potential to facilitate better understanding of mediastinal masses in both pediatric and adult populations.

Value of 18F-FDG PET and PET/CT for evaluation of pediatric malignancies

Successful management of solid tumors in children requires imaging tests for accurate disease detection, characterization, and treatment monitoring. Technologic developments aim toward the creation of integrated imaging approaches that provide a comprehensive diagnosis with a single visit. These integrated diagnostic tests not only are convenient for young patients but also save direct and indirect health-care costs by streamlining procedures, minimizing hospitalizations, and minimizing lost school or work time for children and their parents. (18)F-FDG PET/CT is a highly sensitive and specific imaging modality for whole-body evaluation of pediatric malignancies. However, recent concerns about ionizing radiation exposure have led to a search for alternative imaging methods, such as whole-body MR imaging and PET/MR. As we develop new approaches for tumor staging, it is important to understand current benchmarks. This review article will synthesize the current literature on (18)F-FDG PET/CT for tumor staging in children, summarizing questions that have been solved and providing an outlook on unsolved avenues.

Update on pediatric leukemia and lymphoma imaging

Together, leukemia and lymphoma account for half of all childhood malignancies. Leukemia and lymphoma arise from similar cell lines and can have overlapping imaging features; however, the clinical presentation, imaging strategies, and treatment protocols can vary substantially based on the specific subtype. Although imaging does not play a central role in staging or monitoring disease in childhood leukemia, findings on imaging may be the first indication of the diagnosis. Advanced imaging, especially positron emission tomography/computed tomography, has moved to the forefront of staging and treatment response evaluation in Hodgkin's disease and non-Hodgkin's lymphoma. Imaging also plays a key role in evaluating the myriad of treatment complications that are commonly seen with chemotherapy and associated neutropenia. Future efforts will be largely focused on decreasing radiation exposure to these children, utilizing reduced or radiation-free modalities, such as positron emission tomography/magnetic resonance and diffusion-weighted whole-body imaging with background suppression, as well as refining surveillance imaging strategies. The purpose of this article is to briefly review the classification of pediatric leukemia and lymphoma, illustrate common imaging findings at presentation throughout the body, describe staging and therapeutic response evaluation, and show a spectrum of commonly encountered complications of treatment.

Potential Pediatric Applications of PET/MR

Medical imaging with multimodality and whole-body technologies has continuously improved in recent years. The advent of combined modalities such as PET/CT and PET/MR offers new tools with an exact fusion of molecular imaging and high-resolution anatomic imaging. For noninvasive pediatric diagnostics, molecular imaging and whole-body MR have become important, especially in pediatric oncology. Because it has a lower radiation exposure than PET/CT, combined PET/MR is expected to be of special use in pediatric diagnostics. This review focuses on possible pediatric applications of PET/MR hybrid imaging, particularly pediatric oncology and neurology but also the diagnosis of infectious or inflammatory diseases.

The utility of FDG PET in diagnosis and follow-up of lymphoma in childhood

Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL) are among the most common malignancies of childhood. (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) can be employed for accurate staging, treatment planning, and response assessment in pediatric patients with lymphomas, taking advantage of the increased FDG uptake of the malignant cells, secondary to their increased metabolic needs. FDG PET has higher sensitivity than other imaging modalities to detect nodular or diffuse lesions and higher sensitivity than bone marrow biopsy to detect bone marrow infiltration. FDG PET consists of an invaluable imaging modality during evaluation and treatment of pediatric lymphomas.

Interim PET response criteria in paediatric non-Hodgkin's lymphoma. Results from a retrospective multicenter reading

AIM

To evaluate the use and reliability of the PET-based response criteria for interim PET (iPET) in terms of interobserver variability in pediatric and adolescent patients suffering from non-Hodgkin´s lymphoma (NHL). Particular attention was given to the identification of visual cutoff to separate patients with a favourable outcome.

PATIENTS, METHODS

Retrospective analysis of PET-datasets of 18 children and adolescents suffering from NHL who underwent iPET after two cycles of chemotherapy for response assessment. Datasets were evaluated and rated in three independent review centers (RC) (blinded-read, intra-center consensus) using a visual 5-point response scale. Ratings were compared to clinical outcome. Pairwise interobserver agreement was analysed with Cohen's kappa-test (κ). Overall agreement (between attended RCs) was assessed with Fleiss' κ-test.

RESULTS

Four patients suffered relapse (early, n = 2; late, n = 2). Per region analyses on interobserver variability revealed a "substantial" agreement (Fleiss' κ = 0.618). Per patient analyses revealed concordant iPET-ratings in eight patients: iPET-negative (iPET-), n = 5; iPET-positive (iPET+), n = 2; iPET-inconclusive (iPET±), n = 1. Discordant ratings were found in the remaining patients. Patients with early relapse were concordantly identified using mediastinal blood pool structures (MBPS, score ≥ 3) as visual cutoff between iPET+ or iPET-, respectively. However, patients with late relapse were not concordantly identified taking the MBPS as visual cutoff.

CONCLUSION

The iPET interpretation using a dedicated PET-based response scale assured a low interobserver variability in per-region but not in per-patient analyses in a multicenter read. Using a sensitive read out (iPET+, score ≥ 3) a reliable identification of patients suffering relapse was limited to those with early relapse.

FDG PET/CT in children and adolescents with lymphoma

The aim of this review is to give an overview of FDG PET/CT applications in children and adolescents with lymphoma. Today, FDG PET is used for tailoring treatment intensity in children with Hodgkin lymphoma within the framework of international treatment optimisation protocols. In contrast, the role of this method in children with Non-Hodgkin lymphoma is not well defined. This paper overviews clinical appearance and metabolic behaviour of the most frequent lymphoma subtypes in childhood. The main focus of the review is to summarise knowledge about the role of FDG PET/CT for initial staging and early response assessment.

SUV-measurements and patient-specific corrections in pediatric Hodgkin-lymphoma: is there a benefit for PPV in early response assessment by FDG-PET?

BACKGROUND

To evaluate the influence of different SUV-measurements and patient-specific corrections thereof on the positive predictive value (PPV) of FDG-PET in pediatric Hodgkin lymphoma (pHL) using SUV-based response assessment.

METHODS

PET-datasets of 33 children [female, n = 13, male, n = 20; range of age, 8.0-17.8 (mean, 15.0) years; follow-up, 44.5-83.3 (mean 63.0) months] with HL were analyzed retrospectively. PET-scans were obtained baseline (PET1) and after two cycles of chemotherapy (PET2). Within the leading lesion maximal SUV (SUVmax) and mean SUVs were generated by using isocontur-thresholds for different volumes of interest: Absolute, SUV2.5; relative to SUVmax, SUVmean40% to SUVmean70%. Generated SUVs were adjusted to body weight (SUV) and corrected for body surface area (SUV_BSA), patient's blood glucose and a combination thereof. The decrease in SUV or respective derivates thereof between PET1 and PET2 (ΔSUV) was assessed for response prediction using receiver operating characteristics (ROC)-analysis.

RESULTS

Three patients had recurrence of disease. ROC-analysis showed the most accurate differentiation of responders and non-responders for ΔSUVmax_BSA [AUC, 0.97; P = 0.0026; sensitivity, 100%; specificity, 93.3%; PPV, 60.0%; negative predictive value (NPV), 100%; accuracy, 93.3%]. However, comparable results were obtained for conventional ΔSUVmax-determination (AUC, 0.96; P = 0.0112; sensitivity, 100%; specificity, 90.0%; PPV, 50.0%; NPV, 100%; accuracy, 90.9%). Threshold-based approaches were less effective or technically not performable in all patients.

CONCLUSIONS

At early response assessment by FDG-PET, patient-specific correction of ΔSUVmax by BSA improves PPV without impairment of excellent NPV in pHL. However, it is not statistically superior to simple ΔSUVmax-analyses. Larger cohorts are needed to investigate this observation.

Diagnostic value of combined ¹⁸F-FDG PET/MRI for staging and restaging in paediatric oncology

PURPOSE

The present study compares the diagnostic value of (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) and MRI to combined/registered (18)F-FDG PET/MRI for staging and restaging in paediatric oncology.

METHODS

Over 8 years and 2 months, 270 (18)F-FDG PET and 270 MRI examinations (mean interval 5 days) were performed in 132 patients with proven (n = 117) or suspected (n = 15) malignant disease: solid tumours (n = 64), systemic malignancy (n = 53) and benign disease (n = 15). A total of 259 suspected tumour lesions were analysed retrospectively during primary diagnosis and 554 lesions during follow-up. Image analysis was performed separately on each modality, followed by analysis of combined and registered (18)F-FDG PET/MRI imaging.

RESULTS

A total of 813 lesions were evaluated and confirmed by histopathology (n = 158) and/or imaging follow-up (n = 655) after 6 months. In the separate analysis of (18)F-FDG PET and MRI, sensitivity was 86 %/94 % and specificity 85 %/38 %. Combined/registered (18)F-FDG PET/MRI led to a sensitivity of 97 %/97 % and specificity of 81 %/82 %. False-positive results ((18)F-FDG PET n = 69, MRI n = 281, combined (18)F-FDG PET/MRI n = 85, registered (18)F-FDG PET/MRI n = 80) were due to physiological uptake or post-therapeutic changes. False-negative results ((18)F-FDG PET n = 50, MRI n = 20, combined (18)F-FDG PET/MRI n = 11, registered (18)F-FDG PET/MRI n = 11) were based on low uptake or minimal morphological changes. Examination-based evaluation during follow-up showed a sensitivity/specificity of 91 %/81 % for (18)F-FDG PET, 93 %/30 % for MRI and 96 %/72 % for combined (18)F-FDG PET/MRI.

CONCLUSION

For the detection of single tumour lesions, registered (18)F-FDG PET/MRI proved to be the methodology of choice for adequate tumour staging. In the examination-based evaluation, MRI alone performed better than (18)F-FDG PET and combined/registered imaging during primary diagnosis. At follow-up, however, the examination-based evaluation demonstrated a superiority of (18)F-FDG PET alone.

Review of Clinical Applications of Fluorodeoxyglucose-PET/Computed Tomography in Pediatric Patients with Lymphoma

[(18)F]fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) imaging is routinely used in the initial diagnosis and response assessment during and immediately after therapy, as well as in the follow-up surveillance. FDG PET/CT outperforms diagnostic CT and other conventional imaging modalities in the evaluation of pediatric patients with lymphoma, with higher sensitivity and specificity, leading to more accurate staging/restaging and modifications of therapeutic strategies. Resolution of FDG-avid lesions in the early post-therapy phase often indicates good response to treatment and better prognosis. FDG PET/CT also outperforms bone marrow biopsy in detecting bone marrow infiltration of lymphoma.

Can fluorodeoxyglucose positron emission tomography/computed tomography avoid negative iliac crest biopsies in evaluation of marrow involvement by lymphoma at time of initial staging?

The assessment of bone marrow involvement (BMI) is important for accurate prognostication and deciding the appropriate therapy in patients with lymphoma. Conventional bilateral iliac crest biopsies (ILBMBs) have many limitations. F-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) is a useful investigative tool for detecting BMI. F-18 FDG PET/CT data for 97 patients with either non-Hodgkin lymphoma (NHL) or Hodgkin lymphoma (HL) were analyzed. ILBMB was performed 7-10 days later. A final diagnosis of BMI was made in 38/97 patients on the basis of composite criteria derived from both FDG PET/CT and ILBMB results. ILBMB detected BMI in 29/38 patients, 2/5 patients with HL, 27/33 patients with NHL, 19/25 patients with aggressive NHL, and 8/8 patients with indolent NHL with a sensitivity of 76%, 40%, 82%, 76%, and 100%, respectively. FDG PET/CT was true positive for BMI in 5/5 patients with HL and 29/33 patients with NHL, comprising 25/25 patients with aggressive NHL and 4/8 patients with indolent NHL, with a sensitivity of 100%, 88%, 100%, and 50%, respectively. FDG PET/CT performed better than ILBMB in cases of HL and aggressive NHL, but its sensitivity was poor in cases of indolent lymphoma. In addition, FDG PET/CT had a very high negative predictive value approaching 100% in HL and aggressive NHL, which might help in avoiding negative ILBMBs.

Leukemia and lymphoma

Leukemia and lymphoma are the most common and third most common pediatric malignancies, respectively, and share cell lineages, but the clinical and imaging manifestations of these malignancies vary substantially. Along with providing pertinent details on classification, epidemiology, and treatment, this article reviews the current roles of imaging in the management of childhood leukemia and lymphoma, with attention to diagnosis, staging, risk stratification, therapy response assessment, and surveillance for disease relapse and adverse effects of therapy. Advances in functional imaging are also discussed to provide insights into future applications of imaging in the management of pediatric patients with leukemia and lymphoma.

Clinical applications of PET and PET/CT in pediatric malignancies

The common childhood cancers are leukemia, CNS tumors, lymphomas, soft-tissue tumors (such as rhabdomyosarcoma and fibrosarcoma), neuroblastoma, malignant bone tumors, germ cell tumors with neoplasms of gonads and hepatic tumors. Usually the conventional imaging modalities, such as x-ray, ultrasound, computed tomography (CT) and MRI, are being routinely used for the management of these pediatric malignancies. However, most of these modalities provide structural information and are lacking in functional/metabolic status of these malignancies. Recently, PET and PET/CT have emerged as a functional diagnostic imaging modality for the management of various cancers in adult population. Up to now most of the data published in the literature are on PET alone. PET used in conjunction with CT is useful as it provides an enhanced view of the anatomical details and the malignant focus then can be located with highest accuracy. PET and PET/CT has been found to be useful in, for example, CNS tumors, lymphomas, soft-tissue tumors, neuroblastoma, malignant bone tumors and germ cell tumors. PET/CT has a limited role in early diagnosis, however, it plays an important role in initial staging, treatment response evaluation and detection of metastatic disease in these cancers. Despite the fact that PET/CT has better diagnostic value when compared with conventional imaging, such as CT and MRI, in the management of many pediatric cancers, there are certain limitations. PET/CT has a limited role in detection of lesions smaller than 5 mm, well-differentiated tumors and tumors with low metabolic rate. Many infections and inflammation can lead to false-positive PET/CT results. In the present review we will discuss the various clinical indications of PET and PET/CT in pediatric cancers.

Emerging non-transplant-based strategies in treating pediatric non-Hodgkin's lymphoma

Lymphomas represent the third most common cancer in children and adolescents. The non-Hodgkin's lymphomas comprise a heterogeneous group of tumors, with distinct clinical and pathologic features. Although intensive multi-agent chemotherapy has made non-Hodgkin's lymphoma one of the most curable malignancies in children and young adults, there is room for improvement in treatment, particularly for those with advanced-stage disease and those who relapse after conventional therapy. New approaches are now attempting to reduce the burden of treatment, to focus on novel and more specific biologic targets, and to improve outcomes for patients with advanced-stage disease while reducing the potential for late effects. A comprehensive review of all potential agents is beyond the scope of this review, which will focus on some of the newer strategies for treating non-Hodgkin's lymphoma that are coming into clinical use today.

18F-FDG PET/CT in paediatric lymphoma: comparison with conventional imaging

PURPOSE

In children with Hodgkin's disease and non-Hodgkin's lymphoma, the ability of (18)F-fluoro-2-deoxy-D-glucose PET/CT and conventional imaging (CI) to detect malignant lesions and predict poor lesion response to therapy was assessed and compared.

METHODS

A retrospective review of findings reported on PET/CT and CI was performed using a lesion-based analysis of 16 lymph node and 8 extra-nodal regions. Lesions were defined by histopathological findings or follow-up > 6 months.

RESULTS

The study included 209 PET/CT scans with a valid CI comparator. A total of 5,014 regions (3,342 lymph node, 1,672 extra-nodal) were analysed. PET/CT performed significantly better than CI in the detection of malignant lesions with sensitivity and specificity of 95.9 and 99.7% compared to 70.1 and 99.0%, respectively. For predicting poor lesion response to therapy, PET/CT had fewer false-positive lesions than CI. The specificity for predicting poor lesion response to treatment for PET/CT was 99.2% compared to 96.9% for CI. PET/CT was the correct modality in 86% of lesions with discordant findings.

CONCLUSION

PET/CT is more accurate than CI in detecting malignant lesions in childhood lymphoma and in predicting poor lesion response to treatment. In lesions with discordant findings, PET/CT results are more likely to be correct.

(18)F-FDG PET in Pediatric Lymphomas: A Comparison with Conventional Imaging

This study reports on our experience with 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in pediatric patients affected by Hodgkin's disease (HD) and non-Hodgkin's lymphoma (NHL). We studied 20 pediatric subjects (12 males, 8 females; mean age, 10 years; range, 6 months to 14 years) with malignant lymphoma (9 HD, 11 NHL) for a 4-year period of time. Overall, 45 PET scans were performed: 7 at disease presentation and 38 for evaluation of response to therapy or follow-up study. All PET results were compared with conventional imaging (CI), mainly computed tomography (CT) and/or magnetic resonance imaging (MRI), and supported by clinical follow-up and/or histologic data. In 18 of 20 patients, PET findings correctly identified the status of disease. Two (2) subjects (respectively, 1 HD and 1 NHL, both at follow-up) resulted falsely positive: 1 due to prominent thymic uptake, and the other due to nonspecific inflammation. Of 45 scans, PET findings were consistent with clinical follow-up and other CI data in 43 cases (16 true-positive and 27 true-negative results) and resulted falsely positive in the remaining 2 scans. On a lesion-by-lesion basis (overall, 153 lesions: 84 nodal and 69 extranodal), we found a concordance between CI and PET findings in 25 nodal (29.8%) and in 22 extranodal sites (32%). PET was more accurate than CI, as it identified active disease in 1 patient negative at CI and excluded relapse in 6 patients with inconclusive CI and in 2 patients with a falsely positive CI. Overall, PET sensitivity and specificity was 100% and 93% versus 94% sensitivity and 72.4% specificity for CI. This comparative study shows FDG PET to be more accurate than CI in evaluating children with lymphoma. Our data also confirms that (18)F-FDG PET may show false-positive findings.

Role of FDG-PET in the definition of involved-field radiation therapy and management for pediatric Hodgkin's lymphoma

PURPOSE

To evaluate positron emission tomography-computed tomography (PET-CT) influences in involved-field radiation therapy (IFRT) field design in pediatric Hodgkin's lymphoma (HL).

MATERIALS AND METHODS

From June 2003 to February 2008, 30 pediatric HL patients were treated at Children's Healthcare of Atlanta (CHOA) and Emory University Department of Radiation Oncology with both chemotherapy and IFRT. Diagnostic contrast-enhanced CT and PET-CT were coregistered using image fusion software. Both were reviewed for all potential sites of involvement and correlated to determine concordance and discordance. They were used in IFRT planning to determine the influence of PET-CT on target volumes and field design.

RESULTS

There were 546 regions analyzed by both PET and CT modalities. Image sets were concordant in 468 regions and discordant in 78, yielding 86% concordance overall. Analysis by weighted κ statistic showed "intermediate to good" fit overall and for nodal sites, but "poor" agreement for extranodal sites. If discordant, a site was most likely PET+/CT-. Integration of PET information caused a change in staging in 15 (50%) patients, 7 upstaged and 8 downstaged. The IFRT volumes were adjusted on the basis of initial PET-CT finding in 21 (70%) patients, with 32 sites added and 15 excluded. There were four relapses, only one outside IFRT fields, but all were successfully salvaged.

CONCLUSION

PET-CT represents an important tool in the management of pediatric patients with HL and has a substantial influence on both initial staging and radiation treatment target definition and field design.

Bone and [18F]fluorodeoxyglucose positron-emission tomography/computed tomography scanning for the assessment of osseous involvement in Hodgkin lymphoma in children and young adults

To compare FDG PET/CT and bone scans for the management of young patients with Hodgkin lymphoma (HL). Eighteen patients, aged 7-24 years, with HL received bone and PET scans within 2 weeks--11 at diagnosis and 7 at known or suspected relapse (37 scan pairs). In six patients (nine scan pairs) both studies were positive. In four patients (five scan pairs), PET showed involvement not evident on bone scan. In four patients (four scan pairs), one of the studies was equivocal and the other negative. In one patient, bone scan showed abnormal uptake in a benign lesion. In nine patients (19 scan pairs), both studies were negative. All osseous metastases identified on bone scan were present on PET. Many additional sites of bony involvement were identified on PET. The bone scan may be safely eliminated.

Role of PET/CT in malignant pediatric lymphoma

INTRODUCTION

Malignant pediatric lymphoma accounts for 10-15% of all pediatric cancers, (representing 2-3% of all malignancies), with a peak incidence between 5-9 years. Chemotherapy is usually the first and most common mode of treatment. The choice of treatment and prediction of prognosis depend on the histological type of tumor, initial staging, evaluating treatment response, and detection of early recurrence. Conventional imaging modalities have many limitations. PET/CT is more accurate, however so far the literature lacks the results of a large group of patients.

AIM OF STUDY

To report the role of PET/CT in the above-mentioned objectives at the newly established Children's Cancer Hospital in Cairo, Egypt, which is one of the busiest dedicated pediatric oncology centers of such purposes in the world. All findings were proven by histopathology, clinically, and by clinical follow-up.

PATIENT POPULATION

A total of 152 patients (35 girls and 117 boys) with histologically proven malignant lymphoma (117 HD, 35 NHL) were included in this study. They were divided into four groups. Group I: 41 patients for initial staging. Group II: 51 patients for evaluating early treatment response after two to three cycles of chemotherapy. Group III: 42 patients for evaluating treatment response 4-8 weeks after the end of their treatment. Group IV: 18 patients evaluated for long-term follow-up. Results of PET/CT were compared with the other conventional imaging modalities (CIM).

RESULTS

The sensitivity, specificity, accuracy, and positive and negative predictive values of PET/CT and CIM were as follows: In Group I: PET/CT modified staging and treatment in 11 out of 41 cases (26.8%), upstaged 5(12.2%) patients and down-staged six (14.6%) patients. Group II: 100%, 97.7%, 98%, 85.7%, 100%, respectively, for PET/CT and 83%, 66.6%, 68.6%, 25%, 96.7% for CIM respectively Group III: At the end of chemotherapy 100%, 90.9%, 92.8%, 75%, 100%, respectively, for PET/CT and 55.5%, 57.5%, 57.1%, 26.3%, 82.6% for CIM, respectively. Group IV: For long-term follow-up, all the parameters scored 100% for PET/CT, 100%, 38.4%, 72.2%, 50%, 100% for CIM, respectively.

CONCLUSION

PET/CT in pediatric lymphoma is more accurate than CIM. We recommend that it should be the first modality for all purposes in initial staging, evaluating treatment response and follow-up.

Early and late therapy response assessment with [18F]fluorodeoxyglucose positron emission tomography in pediatric Hodgkin's lymphoma: analysis of a prospective multicenter trial

PURPOSE

In adult Hodgkin's lymphoma (HL) risk stratification after early therapy response assessment with [(18)F]fluorodeoxyglucose (FDG) positron emission tomography (PET) seems to allow tailoring therapy with less toxicity for patients with adequate metabolic response. This study delivers the first prospective data on the potential of FDG-PET for response assessment in pediatric HL.

PATIENTS AND METHODS

FDG-PET was performed in 40 pediatric HL patients before polychemotherapy (PET-1), after two cycles of polychemotherapy (PET-2), and after completion of polychemotherapy (PET-3). Mean follow-up was 46 months (range, 26 to 72 months).

RESULTS

At early and late response assessment, the proportion of PET-negative patients was significantly higher compared with those patients with negative findings in conventional imaging methods (CIMs; PET-2, 26 of 40 v CIM-2, one of 40; P < .001; PET-3, 21 of 29 v CIM-3, four of 29; P < .001). Sensitivity and negative predictive value were 100% for early and late therapy response assessment by PET. Both patients suffering a relapse during follow-up were identified by PET-2/3, whereas one of these patients was not detected by CIM-3. PET was superior to CIMs with regard to specificity in early and late therapy response assessment (68% v 3%, and 78% v 11%, respectively; both P < .001). Specificity of early therapy response assessment by PET was improved to 97% by quantitative analysis of maximal standardized uptake value reduction using a cutoff value of 58%.

CONCLUSION

Pediatric HL patients with a negative PET in response assessment have an excellent prognosis while PET-positive patients have an increased risk for relapse.

FDG PET and PET/CT in the Management of Pediatric Lymphoma Patients

Fluorodeoxyglucose (FDG) PET has an ever-increasing role in the management of Hodgkin's and non-Hodgkin's lymphomas, which has been demonstrated in numerous studies in the adult population. In children and adolescents, however, only a limited number of studies have investigated the role of FDG PET in lymphoma. This article reviews the currently available literature on the clinical application of FDG PET in the management of childhood lymphoma. The authors believe that FDG PET (and especially PET/CT) is a valuable imaging modality in the initial diagnosis, response assessment, and post-therapy residual evaluation of Hodgkin's and FDG-avid non-Hodgkin's lymphomas in children and adolescents, and will have a significant impact on the clinical management of pediatric lymphoma.

Guidelines for 18F-FDG PET and PET-CT imaging in paediatric oncology

OBJECTIVE

The purpose of these guidelines is to offer to the nuclear medicine team a framework that could prove helpful in daily practice. These guidelines contain information related to the indications, acquisition, processing and interpretation of (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) in paediatric oncology. The Oncology Committee of the European Association of Nuclear Medicine (EANM) has published excellent procedure guidelines on tumour imaging with (18)F-FDG PET (Bombardieri et al., Eur J Nucl Med Mol Imaging 30:BP115-24, 2003). These guidelines, published by the EANM Paediatric Committee, do not intend to compete with the existing guidelines, but rather aim at providing additional information on issues particularly relevant to PET imaging of children with cancer.

CONCLUSION

The guidelines summarize the views of the Paediatric Committee of the European Association of Nuclear Medicine. They should be taken in the context of "good practice" of nuclear medicine and of any national rules, which may apply to nuclear medicine examinations. The recommendations of these guidelines cannot be applied to all patients in all practice settings. The guidelines should not be deemed inclusive of all proper procedures or exclusive of other procedures reasonably directed to obtaining the same results.

Imaging of pediatric lymphomas

Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL) represent 10% to 15% of all malignancies occurring in children younger than 20 years of age. Advances in cross-sectional imaging and the availability of positron emission tomography (PET) and PET-CT have had a major impact on imaging and management of pediatric patients. This article reviews the clinical features of lymphoma, focusing on the spectrum of imaging findings seen in diagnosis, staging, and follow-up of HL and NHL. Pediatric NHL has four major histologic subtypes: Burkitt lymphoma, diffuse large B-cell lymphoma, anaplastic large cell lymphoma, and lymphoblastic lymphoma. The most important subtype of HL is nodular sclerosis.