Role of 18- Fluoro Deoxyglucose Positron Emission Tomography in Children with Leukemia

Introduction

18-Fluoro deoxyglucose positron emission tomography (FDG-PET) is a noninvasive imaging tool for initial staging and evaluation of treatment response in several malignancy. Role of FDG-PET scan is extensively studied for lymphoma and recently findings were incorporated into the response criteria but there is lack of data for pediatric leukemia in this field. The purpose of this study was to evaluate the role of FDG-PET for disease status, for determining the effect of therapy and predicting the prognosis of pediatric leukemia.

Methods

We retrospectively reviewed the results of FDG-PET in 20 leukemic children treated in our department from 2005 to 2015. Whole body PET scans were performed at initial diagnosis in only two patients (2 ALL), after the first line therapy in 3 patients (3 ALL), at relapse in 6 patients (5 lymphoma-leukemia, 1 ALL) and in 9 patients following allogeneic stem cell transplantation (Allo-SCT) (5 AML, 4 ALL) for evaluation of disease status. Maximum standardized uptake values (SUVmax) were used to assess the results of FDG-PET scan. All data were analysed by SPSS 15.0 programme.

Results

Twenty patients were enrolled in our study, 14 boys and 6 girls. Median age was 11 years (range 2 -17). Treatment response was evaluated with FDG-PET in consecutive 20 patients and 9 were negative PET scan. From these patients, two showed relapsed in a median of 20 months after their negative scan and one with surgically removed chloroma lesion was also negative PET scan. The other six patients were in complete remmision. The remaining 11 patients were positive PET scan, which was multifocal bone marrow (BM) lesions in 3 patients after allo-SCT, diffuse BM involvement in 2 patients at diagnosis and either multifocal different area (spleen, kidney, BM) or diffuse BM lesions in 6 patients at relapse. SUVmax value was significantly higher in patients with multifocal lesions (8.6±3.2) than those of patients with diffuse involvement (3.4±0.9) (p<0.05). However, only three cases showed discordant results on FDG-PET and BM biopsy following allo-SCT. These three cases with negative BM biopsy had multifocal BM lesions in PET scan simultaneously but later developed BM relapse in a median of 2 months after positive scan. Their PET scans after salvage chemotherapy were negative. Event free survival of the PET negative groups (55.6%) were insignificantly better than those of PET positive groups (18.2%) (p>0.05).

Conclusions

To our knowledge, there are no previous studies associated with FDG-PET values in children with leukemia. Although our results should be confirmed in a prospective study in a large number of patients, we believe that FDG-PET value may guide physicians to show multifocal BM lesions for possible early relapse, even if BM examination indicate normal and thus it may also be helpful to identify high risk leukemic patients who need a more intensive treatment approach.