Interest of 18 FDG-PET to confirm complete response (CR) after induction chemotherapy in paediatric Burkitt’s lymphomas (BL)

Objectives BL is a rare and highly aggressive form of B cell lymphoma but also one of the more curable form using intensive chemotherapy. Obtaining a CR at the end of induction chemotherapy is one of the major prognostic factor. The objective of this study was to evaluate, retrospectively, the interest of FDG-PET to confirm CR after induction chemotherapy in paediatric BL.

Methods 18 children, median age 9 years [3-17], with BL stage II (n=2), stage III (n=9) and stage IV (n=7), treated according to french LMB 2001 protocol beetween 2005 et 2011 were included. 18 FDG PET were performed in addition to conventional imaging (CI) including CT +/-ultrasound +/-MRI after 2 (stage II), 3 (stage III) or 4 (stage IV) courses of chemotherapy. 18FDG-PET were interpreted according to IHP criteria. The gold standard was the follow up and/or histology.

Results FDG-PET were negative in 11 children and were in agreement with CI in 9/11 cases. The two discordant cases, confirmed by histology, were considered as true negative for FDG-PET. The negative predictive value of FDG-PET was 100% versus 81% for CI. FDG-PET and CI were positive in 7 children. According to histology, only 1/7 was considered as a true positive: it was the only case with residual mass uptake higher than liver background. The positive predictive value of FDG-PET was 14% versus 11% for CI.

Conclusions FDG-PET seems to be interesting to confirm CR at the end of induction chemotherapy and could limit the systematic use of biopsy. However, using IHP criteria, biopsy remains essential to characterize FDG-PET positive residual masses