LAUSR

To investigate if baseline [18F]FDG PET/CT can predict the outcome of follicular lymphoma (FL) in patients managed with an initial “watch-and-wait” approach. Thirty-eight newly diagnosed FL patients who were managed with an initial “watch-and-wait” approach and undergone baseline [18F]FDG PET/CT were retrospectively enrolled. The standard uptake value (SUV), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) of FL lesions were measured on PET/CT. Patients were followed up for at least 24 months or until initiation of FL therapy. The endpoint was the time to initiation of lymphoma treatment (TLT). After a median follow-up of 28 months (range 3–94 months), lymphoma treatment was initiated in 21/38 (55.3%) patients (median 15 months, range 3–51 months). Patients with TLT < 24 months showed SUVmax and TLG values significantly higher than those with TLT ≥ 24 months (p < 0.05). Receiver operating characteristic analysis demonstrated cutoff values of SUVmax > 9.5, MTV > 90.62 ml, and TLG > 144.96 SUVbw*ml were optimal for predicting TLT < 24 months. Kaplan-Meier analysis showed SUVmax > 9.5, MTV > 90.62 ml, and TLG > 144.96 SUVbw*ml had statistically significant correlations with shorter TLT (p < 0.01). Lymph node regions ≥ 3 and lymph nodes > 3 cm had almost significance (p < 0.1). In multivariate analysis, SUVmax > 9.5 (HR 3.2 [95% CI 1.1–9.2], p = 0.033) and TLG > 144.96 SUVbw*ml (HR 9.3 [95% CI 1.8–47.7], p = 0.008) were demonstrated to be independent predictive factors for shorter TLT. Metabolic indices (SUVmax and TLG) of baseline [18F]FDG PET/CT could predict the outcome independently in FL patients under an initial “watch-and-wait” approach. • “Watch-and-wait” approach is part of the overall treatment plan in asymptomatic patients with low tumor burden FL. However, the time to initiation of active treatment varies from months to years. • In our retrospective study of 38 patients with FL managed with an initial “watch-and-wait” approach, the SUVmax and TLG were demonstrated to be independent predictive factors for time to initiation of FL treatment. • Baseline [18F]FDG PET/CT may help to better select patients with FL who are most likely to benefit from “watch-and-wait” management.