The role of FDG-PET/CT in the evaluation of residual disease in paediatric non-Hodgkin lymphoma

Update on FDG-PET in pediatric lymphoma

Lymphoma represent the third most common malignant disease in childhood and adolescence. They are divided into pediatric Hodgkin lymphoma (P-HL) and pediatric non-Hodgkin lymphoma (P-NHL). In P-HL, excellent cure rates are achieved through combined modality treatment using chemotherapy and radiotherapy. For more than 20 years, FDG-PET has been an integral part of the treatment and guides its intensity through improved staging and precise assessment of chemotherapy response. In P-NHL, good cure rates are achieved with chemotherapy alone. At present FDG-PET plays only a subordinate role in the treatment setting. Its potential to contribute to treatment management is far from being fully utilised. In this article, the current status of FDG-PET in pediatric lymphoma is presented in detail. The core elements are the sections on staging and response assessment. In addition, challenges and pitfalls are discussed and future developments are outlined.

No difference in treatment outcome between patients with nodal versus extranodal diffuse large B-cell lymphoma

Background and Aim

Diffuse large B-cell lymphoma (DLBCL) has been classified using various parameters, including the site of origin. Studies have reported conflicting outcomes when DLBLC patients were stratified according to the site of origin. This study aimed to investigate the response rate and survival outcomes in nodal versus extranodal DLBCL and compare the results to a region-matched study covering the 1988 - 2005 period.

Methods

A single-center retrospective cohort study was conducted on all patients diagnosed with DLBCL and treated in a tertiary care hospital in Pakistan during 2014 - 2019. We calculated the mean and median for continuous variables and frequency and percentages for all categorical variables. Progression-free survival (PFS) and overall survival (OS) were calculated using Kaplan-Meier survival curves. A Cox proportional hazards model was used to determine the hazard ratio (HR) for OS.

Results

Of the 118 patients, 49 patients (41.5%) had nodal disease and 69 patients (58.5%) were diagnosed with extranodal DLBCL. The majority of patients in the nodal and extranodal cohorts presented with Stages III and IV disease (73.4% and 62.3%, respectively). A complete response to (immuno) chemotherapy was achieved in 71.4% of nodal DLBCL patients and 65.2% of extranodal DLBCL patients. The 5-year PFS and median PFS in the entire cohort were 0.8% and 17 m, respectively. The PFS and median PFS in the nodal and extranodal DLBCL cohort were 0% and 1.4%, respectively, and 15 m and 19 m, respectively. The 5-year OS and median OS in the entire cohort were 16.1% and 19 m, respectively. The OS and median OS in the nodal and extranodal DLBCL cohort were 8.2% and 21.7%, respectively, and 19 m and 21 m, respectively. Multivariable linear regression revealed that the ABC phenotype (nodal, HR = 1.37, 95% CI = 1.37 - 3.20; extranodal, HR = 1.65, 95% CI = 1.46 - 3.17; GBC as reference) and double and triple hit DLBCL (nodal, HR = 1.29, 95% CI = 1.19 - 2.81; extranodal, HR = 1.87, 95% CI = 1.28 - 2.43; and non-expressors as reference) are independent negative predictors of OS.

Conclusions

DLBCL incidence in the Karachi region has remained comparable but patient composition in the extranodal DLBCL cohort has shifted to predominantly advanced stage. Nodal and extranodal DLBCL were associated with similar PFS and OS profiles and first- and second-line treatment responses. Cell of origin and antigen expression status was independent negative predictors of OS, disfavoring the ABC phenotype and lesions with c-MYC and BCL2 and/or BCL6 overexpression.

Relevance for Patients

DLBCL is an aggressive type of non-Hodgkin's lymphoma, however; patients respond well to standard systemic chemotherapy. Extranodal type of DLBCL patients tend to have more residual disease after first-line systemic chemotherapy, but physicians should keep in mind that the subsequent line treatment mitigates its negative impact on survival.

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.

Overview and recent advances in PET/CT imaging in lymphoma and multiple myeloma

Imaging in hematological diseases has evolved extensively over the past several decades. Positron emission tomography/computed tomography (PET/CT) with of 2-[18 F]-fluoro-2-deoxy-d-glucose ([18 F] FDG) is currently essential for accurate staging and for early and late therapy response assessment for all FDG-avid lymphoproliferative histologies. The widely adopted visual Deauville 5-point scale and Lugano Classification recommendations have recently standardized PET scans interpretation and improved lymphoma patient management. In addition [18 F] FDG-PET is routinely recommended for initial evaluation and treatment response assessment of Multiple Myeloma (MM) with significant contribution in risk-stratification and prognostication, although magnetic resonance imaging remains the Gold Standard for the assessment of bone marrow involvement. In this review, an overview of the role of [18 F] FDG-PET, in hematological malignancies is provided, particularly focusing on Hodgkin lymphoma (HL) and Diffuse Large B Cell Lymphoma (DLBCL), both in adult and pediatric populations, and MM, at each point of patient management. Potential alternative molecular imaging applications in this field, such as non-[18 F] FDG-tracers, whole body magnetic resonance imaging (WB-MRI), hybrid PET/MRI and emerging radiomics research are briefly presented.

Clinical Utility of Radiologic Disease Reassessment in the Management of Pediatric B-Cell Non-Hodgkin Lymphoma

Although outcomes for children with B-cell non-Hodgkin lymphoma are excellent, between 20% and 40% demonstrate residual radiologic abnormalities at disease assessment during consolidation therapy, the significance of which remains uncertain. The authors report the outcomes for all children treated for B-cell non-Hodgkin lymphoma at our center over an 11-year period. Twenty-four of 64 (38%) children had residual radiologic abnormalities at disease remission assessment. Seven (29%) underwent histologic biopsies that were normal. No children with residual radiologic abnormalities experienced disease relapse or death, suggesting that imaging at this time point creates clinical uncertainty without indicating residual disease or predicting relapse.

18Fluorine-fluorodeoxyglucose PET/CT Imaging in Childhood Malignancies

Objectives:

The aim of the study was to evaluate the utility of ¹⁸fluorine-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) in the diagnosis, staging, restaging, and treatment response of childhood malignancies.

Methods:

This study included 52 patients (32 boys, 20 girls) who were referred to our clinic between November 2008 and December 2018 with the diagnosis of malignancy. The patients were evaluated retrospectively. Median age of the patients was 13 years (range 2-17). ¹⁸F-FDG was given to the patients intravenously, and time of flight with PET/16 slice CT was performed 1 hour thereafter. The lowest dose was 2 mCi (74 MBq) and the highest dose was 10 mCi (370 MBq). Fasting blood sugars of all patients were found below 200 mg/dL (11.1 mmol/L).

Results:

¹⁸F-FDG PET/CT was performed to evaluate the response to treatment in 38 of 52 children, staging in 11 patients (staging and evaluation of the response to treatment in nine of them), restaging in 2 patients, restaging, and evaluation of the response to treatment in 1 patient. ¹⁸F-FDG PET/CT examination was reported as normal in 13 patients (5 girls, 8 boys). The pathological ¹⁸F-FDG uptake was detected in 39 patients (14 girls, 25 boys), which indicated metastasis and/or recurrence of the primary disease. Total number of deaths was 30 (13 girls, 17 boys).

Conclusion:

¹⁸F-FDG PET/CT has a significant role for staging, restaging, treatment response, and detection of metastatic disease but it is limited for the early diagnosis of childhood cancers

Can FDG-PET replace biopsy for the evaluation of residual tumor in pediatric mature B-cell non-Hodgkin lymphoma?

INTRODUCTION

The aim of our study is to evaluate the role of ¹⁸ F-labeled fluorodeoxy glucose positron emission tomography (¹⁸ FDG-PET) scan for the detection of viable residual mass in pediatric mature B-cell non-Hodgkin lymphoma (NHL). This study also aims to detect the negative predictive value, positive predictive value (PPV), sensitivity, and specificity of ¹⁸ FDG-PET.

PATIENTS AND METHODS

A retrospective, cross-sectional nonrandomized study was carried out. We included all patients with newly diagnosed mature B-cell NHL treated at the Children Cancer Hospital Egypt during the period between July 2007 and the end of May 2018. Patients were included in the study if they (a) had a residual tumor mass, (b) underwent an ¹⁸ FDG-PET scan, and (c) had a pathologic documentation of this residual tumor. Patients were followed up till June 2019.

RESULTS

Thirty-six patients were included, for whom 39 biopsies were performed. Mean age was 7.7 years. Median follow-up period was 52.8, range 6.1 to 117 months.¹⁸ FDG-PET scan was positive (Deauville score 3, 4, or 5) in 24 of 39 patients (61.5%), while it was negative (Deauville score 1 or 2) in 15 patients (38.5%). Positive ¹⁸ FDG-PET scan and biopsy were performed in 15 of 39 samples (38.4%; true positive, TP), while they were both negative in 13 samples (33.3%; true negative). Nine patients (23%) had positive scan and a negative biopsy (false positive), while 2 patients had negative uptake and a positive biopsy (false negative, FN)). Sensitivity of the ¹⁸ FDG-PET scan was 88.2% and specificity was 59.1%. PPV was 62.5% and NPPV was 86.6%.

CONCLUSION

Changing therapy on the basis of a positive finding alone at the time of evaluation is not recommended. FN results exist, so biopsy confirmation is required to avoid the missing refractory disease. If negative, ¹⁸ FDG^- PET can replace a biopsy if the latter is inaccessible or carries an unnecessary risk.

Pediatric Aggressive Mature B-Cell Lymphomas, Version 2.2020, NCCN Clinical Practice Guidelines in Oncology

Pediatric aggressive mature B-cell lymphomas are the most common types of non-Hodgkin lymphoma in children, and they include Burkitt lymphoma (BL) and diffuse large B-cell lymphoma (DLBCL). These diseases are highly aggressive but curable, the treatment is complex, and patients may have many complicated supportive care issues. The NCCN Guidelines for Pediatric Aggressive Mature B-Cell Lymphomas provide guidance regarding pathology and diagnosis, staging, initial treatment, disease reassessment, surveillance, therapy for relapsed/refractory disease, and supportive care for clinicians who treat sporadic pediatric BL and DLBCL.

Quintessential Role of 18Fluorine Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in Differentiation of Viable Tumor Tissue and Nondisease Desmoplastic Residue

The authors report a series of cases of treated nodal, solid malignancies showing persisting physical residue after completion of treatment with 18-F fluorodeoxyglucose positron emission tomography-computerized tomography showing non-avid status conjuring a nondisease desmoplastic residue over morphological disease.

Investigating the potential benefit of second biopsy of residual mass in pediatric mature B cell non-Hodgkin lymphoma

OBJECTIVES

To assess the impact of second-look biopsy of residual mass during or after chemotherapy in pediatric mature B-cell NHL.

METHODS

Patients with mature B-cell non-Hodgkin lymphoma (NHL) who were suspicious of radiological residual mass at mid or end of treatment and subjected to second biopsy were treated at our center between January 2001 and December 2015. Their clinical characteristics, imaging findings, pathological changes, management, and prognosis were reviewed retrospectively.

RESULTS

A total of 31 children were included (13 boys and 18 girls, median age at diagnosis 6.1 years). The median time from diagnosis to second biopsy was 3.15 months (range 2.3-18 months). Biopsy confirmed the presence of viable tumor in eight patients. The specificity and positive predictive value of conventional imaging in detecting residual detectable by biopsy were at 9 and 28.6%, while sensitivity and negative predictive value of this approach were both 100%. Three of the histologic positive patients experienced progressive disease or relapse while the others achieved complete remission (CR) and 21 patients achieved long-time CR at median follow-up of 3.2 years. The median progression-free survival (PFS) time of all 31 was 28 months and 5-year PFS rate was 90.0%. Five-year PFS rate of negative-biopsy and positive-biopsy group were 100 and 62.5%, respectively (p = 0.002).

CONCLUSION

Conventional imaging has very high sensitivity but very low specificity for the accurate determination of residual disease in pediatric NHL. Second-look biopsy is necessary to differentiate viable tumor from necrosis or fibrosis and is solid evidence-based foundation of subsequent treatment.

Post-therapy lesions in patients with non-Hodgkin's lymphoma characterized by 18F-FDG PET/CT-guided biopsy using automated robotic biopsy arm

PURPOSE

The aim of this study was to analyse the positive predictive value (PPV) of post-therapy fluorine-18-fluorodeoxyglucose (F-FDG) PET/CT performed for response or recurrence evaluation in patients with non-Hodgkin's lymphoma (NHL) and to appraise the diagnostic utility of F-FDG PET/CT-guided biopsy in this setting.

PATIENTS AND METHODS

A total of 17 patients with NHL showing F-FDG avid lesions in F-FDG PET/CT performed for response or recurrence assessment underwent F-FDG PET/CT-guided biopsy using automated robotic biopsy arm needle navigation technique. The objectives were analysed in reference to histopathology.

RESULTS

In all, 15 of the 17 (88.5%) procedures yielded adequate representative tissue samples. Nine out of 15 lesions were positive for residual disease and the remaining revealed benign findings on histopathology. One patient with inconclusive biopsy underwent surgical resection and histopathology confirmed the presence of residual disease. PPV of theF-FDG PET/CT was observed to be 62.5% (10/16).

CONCLUSION

F-FDG PET/CT for response evaluation in NHL possesses a low PPV and hence warrants histopathological correlation when F-FDG PET/CT findings influence management decision. Diagnostic yield of F-FDG PET/CT-guided biopsy is high and has the potential to reduce sampling errors.

Paediatric nuclear medicine imaging

BACKGROUND

Nuclear medicine imaging explores tissue viability and function by using radiotracers that are taken up at cellular level with different mechanism. This imaging technique can also be used to assess blood flow and transit through tubular organs. Nuclear medicine imaging has been used in paediatrics for decades and this field is continuously evolving.

SOURCES OF DATA

The data presented comes from clinical experience and some milestone papers on the subject.

AREAS OF AGREEMENT

Nuclear medicine imaging is well-established in paediatric nephro-urology in the context of urinary tract infection, ante-natally diagnosed hydronephrosis and other congenital renal anomalies. Also, in paediatric oncology, I-123-meta-iodobenzyl-guanidine has a key role in the management of children with neuroblastic tumours. Bone scintigraphy is still highly valuable to localize the source of symptoms in children and adolescents with bone pain when other imaging techniques have failed. Thyroid scintigraphy in neonates with congenital hypothyroidism is the most accurate imaging technique to confirm the presence of ectopic functioning thyroid tissue.

AREAS OF CONTROVERSY

Radionuclide transit studies of the gastro-intestinal tract are potentially useful in suspected gastroparesis or small bowel or colonic dysmotility. However, until now a standardized protocol and a validated normal range have not been agreed, and more work is necessary. Research is ongoing on whether magnetic resonance imaging (MRI), with its great advantage of great anatomical detail and no ionizing radiations, can replace nuclear medicine imaging in some clinical context. On the other hand, access to MRI is often difficult in many district general hospitals and general anaesthesia is frequently required, thus adding to the complexity of the examination.

GROWING POINTS

Patients with bone pain and no cause for it demonstrated on MRI can benefit from bone scintigraphy with single photon emission tomography and low-dose computed tomography. This technique can identify areas of mechanical stress at cortical bone level, difficult to demonstrate on MRI, which can act as pain generators. Positron emission tomography (PET) is being tested in the staging, response assessment and at the end of treatment of several paediatric malignancies. PET is becoming more widely utilized in neurology in the pre-surgical assessment of some children with drug resistant epilepsy.

AREAS TIMELY FOR DEVELOPING RESEARCH

The use of PET/MRI scanners is very attractive as it combines benefits of MR imaging with the assessment of cellular viability and metabolism with PET in one examination. This imaging technique will allow important research on tumour in-vivo metabolism (possible applications include lymphomas, neuroblastomas, malignant germ cell tumours andbrain tumours), with the aim of offering a personalized biological profile of the tumour in a particular patient. Ground-breaking research is also envisaged in neurosciences, especially in epilepsy, using PET tracers that would enable a better identification of the epileptogenic focus, and in psychiatry, with the use of radiolabeled neurotransmitters. In paediatric nephro-urology, the identification of the asymptomatic child with ante-natally diagnosed hydronephrosis at risk of losing renal parenchymal function if left untreated is another area of active research involving radionuclide renography.

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.

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.

Systematic review and meta-analysis on the prognostic value of complete remission status at FDG-PET in Hodgkin lymphoma after completion of first-line therapy

This study aimed to systematically review and meta-analyze the prognostic value of complete remission status at 18F-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) in Hodgkin lymphoma after completion of first-line therapy. A systematic literature search was performed in the MEDLINE database for suitable original articles. The included studies were methodologically assessed using the Quality In Prognosis Studies tool. The proportion of patients who developed disease relapse during follow-up, among those patients who were in complete remission according to FDG-PET at the completion of first-line therapy, was calculated for each included study. Heterogeneity in disease relapse proportions across individual studies was assessed using the I2 statistic, with heterogeneity regarded present if I2<50 %. Weighted summary disease relapse proportion was calculated using either a random effects model (if I2>50) or a fixed effects model (if I2≤50). Ten studies comprising a total number of 1137 Hodgkin lymphoma patients with complete remission status according to FDG-PET after completion of first-line therapy were included. Overall methodological quality of included studies was reasonably good. The disease relapse rate during follow-up among all patients with complete remission status at end-of-treatment FDG-PET ranged from 0 to 26.7 %, with a weighted summary proportion of 7.5 % (95 % confidence interval 3.9–13.8 %) using the random effects model (I2=88.3 %). In conclusion, although the disease relapse rate in Hodgkin lymphoma patients who achieve an FDG-PET-based complete remission after first-line therapy is low from an absolute point of view, it is actually high when considering the generally favorable outcome of Hodgkin lymphoma.