Positron Emission Tomography/Computed Tomography before Treatment as a Predictor of ⁹⁰Y-Ibritumomab Tiuxetan Response

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Background and Aims: Radioimmunotherapy (RIT) appears as one of the most effective treatment options for patients with relapsed or resistant non-Hodgkin's lymphoma (NHL). Our aim was to evaluate the role of pre-RIT ¹⁸F-fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) as an early predictor of ⁹⁰Y-Ibritumomab tiuxetan treatment response. Methods: We included consecutive 20 patients with relapsed NHL (10 males; mean age, 58.5±8.9 years old) who were treated with ⁹⁰Y-Ibritumomab tiuxetan. FDG-PET/CT was performed before and after treatment. Semiquantitative parameters of all measurable FDG-avid lesions were measured and averaged. A measurable FDG-avid lesion was defined as a lesion that showed FDG uptake higher than liver with a diameter more than 1cm. Treatment response was determined by visual assessment based on a five-point score criteria from FDG-PET/CT after treatment. Results: Fourteen patients (70%) were classified as responders and the other six patients (30%) as non-responders. All semiquantitative parameters except for MTV demonstrated significantly lower values in the responders compared with the non-responders (p<0.05). Conclusions: Semiquantitative evaluation by SUVmax, SUVpeak, and TLG before treatment were useful as early predictors of ⁹⁰Y-Ibritumomab tiuxetan treatment response.