Role of 18-Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography in Predicting Residual Disease Posttreatment Completion in Retinoblastoma Patients.

Background: Retinoblastoma (RB) is the most common primary intraocular malignancy of childhood. Magnetic resonance imaging (MRI) of the orbit and brain is the preferred imaging modality to diagnose and define extent of disease as well as to assess response to therapy. Sometimes, it may be difficult to differentiate the presence of active residual disease from therapy-related changes based on posttreatment completion MRI. Materials and Methods: RB patients who completed treatment between January 2017 and October 2019 were retrospectively analyzed. We evaluated the utility of F-18-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) to predict active disease in RB patients who continued to have residual disease on MRI at completion of treatment. Results: Out of the 89 patients who completed treatment, dilemma regarding remission status was present in 11 children. All 11 patients underwent FDG-PET-CT. None of them had evidence of metabolically active disease in the orbit, optic nerve, brain, or rest of the body. After a median follow-up of 24 months, no children developed any evidence of disease progression in the form of local or distant relapse. Conclusion: Our results showed that in MRI doubtful cases, a nonavid FDG-PET is reassuring in avoiding further therapy as long as close follow-up can be ensured. FDG-PET-CT may emerge as a useful functional modality to predict disease activity in RB.