Pediatric nonlymphoblastic non-Hodgkin lymphoma: baseline, interim, and posttreatment PET/CT versus contrast-enhanced CT for evaluation--a prospective study.

PURPOSE: To prospectively examine the roles of positron emission tomography (PET)/computed tomography (CT) and conventional contrast material-enhanced CT at baseline, after two cycles of chemotherapy, and after completion of chemotherapy in pediatric patients with nonlymphoblastic non-Hodgkin lymphoma (NHL) who were treated with similar standard treatment protocols.

MATERIALS AND METHODS: The institutional ethics committee approved the study protocol, and all patients were enrolled after written informed consent was obtained. Patients with nonlymphoblastic NHL were prospectively enrolled between January 2008 and March 2010. Patients underwent contrast-enhanced CT and PET/CT for staging and for response assessment after two cycles of chemotherapy (interim) and treatment completion. Complete metabolic response versus no metabolic response at PET/CT and complete response versus no complete response at contrast-enhanced CT was analyzed by using Kaplan-Meier survival analysis.

RESULTS: The final study included 34 patients with nonlymphoblastic NHL (median age, 10.5 years). Baseline PET/CT and contrast-enhanced CT showed concordance in depiction of 112 disease sites; PET/CT depicted 18 more disease sites and two fewer disease sites than contrast-enhanced CT (P = .0003). Disease in five of 34 patients was upstaged, and disease in no patient was downstaged at PET/CT. There was 100% (four of four) concordance between bone marrow involvement at biopsy and stage at PET/CT. The median length of follow-up was 20.3 months. Response at interim PET/CT and contrast-enhanced CT could not predict progression-free survival (PFS) (P = .083 and .18, respectively) or overall survival (OS) (P = .159 and.08, respectively). Posttreatment PET/CT and contrast-enhanced CT findings could predict PFS (P = .036 and .002, respectively) and posttreatment contrast-enhanced CT findings could predict OS (P = .035); however, posttreatment PET/CT findings could not predict OS (P = .067).

CONCLUSION: PET/CT depicts additional sites compared with contrast-enhanced CT and results in upstaging of disease. Either PET/CT or contrast-enhanced CT may be used for response assessment and prognostication in stage III or IV nonlymphoblastic pediatric NHL.