Does 18F-FDG PET/CT have an additive role in evaluation of childhood Langerhans Cell Histiocytosis?

Objectives: To demonstrate the value of FDG PET/CT in evaluation of childhood patient with Langerhans cell histiocytosis (LCH) and its added value in clinical management including initial staging and assessment of treatment response.

Methods: A prospective analysis of 30 patients (27 males and 8 females; age ranged from 2.7 months to 9 years with a mean of 2.7 ± 2.0 years) with histopathological proven LCH who were under treatment and/or regular follow up from September 2013 till November 2016. All patients received specific therapy for LCH in the form of chemotherapy &/or surgical resection according to the standard institutional protocol. The findings of the PET/CT were compared with skeletal survey and computed tomography (CT) findings within time interval less than 1 month. The choice of methods depended on tumor location. Analysis criteria included the following: any focal FDG uptake was considered abnormal when it was greater than that of hepatic uptake or in presence of an abnormal changes on CT with any degree of FDG uptake, FDG avid lymph nodes on PET/CT were interpreted as positive on PET/CT basis regardless of the size.

Results: According to PET/CT result, 21 patients (70%) presented with multi-system disease (bone, LNs, liver, lungs, soft tissue and skin), 6 patients (20%) had unifocal lesions (five with bone and one lymph nodes) and 3 patients (10%) presented by multi-focal lesions (two with bone lesions and a single patient with nodal involvement). At the end of study 21 patients (70%) were disease free with no recurrence. Only nine patients (30%) had disease recurrence. Twenty three patient (76.7%) had low risk of mortality and only seven patients (23.3%) were of high risk state. At the end of study, 21 patients (70%) were disease free with no recurrence. Only nine patients (30%) had disease recurrence. No statistically significant association could be detected between disease recurrence with age, sex, presenting organ, disease extent, risk of mortality, SUVmax of leading lesion. Disease extent showed a border line significant association with risk of mortality (p 0.05).

Conclusion: PET/CT is a useful tool to assess known LCH lesions and rule out the presence of other organ infiltration and to provide a reference basis of classification, staging, treatment plan, and evaluation of therapy effect. FDG PET/CT not only provides the characteristics of lesions in CT scan, but also the lesions activity by FDG uptake. 18F-FDG PET/CT should be incorporated in patient management to facilitate disease stratification and avoid un-necessary interventions. Research Support: none