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 F-labeled fluorodeoxy glucose positron emission tomography ( 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 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 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. 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 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 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, FDG PET can replace a biopsy if the latter is inaccessible or carries an unnecessary risk.