PET interim results could promptly select Follicular Lymphoma patients in need of maintenance therapy. Potential additional value of ctDNA

Background: Follicular Lymphoma (FL) patients frequently achieve long remissions with frontline chemoimmunotherapy (CIT); nevertheless, a subset of will experience early progression and poor outcome. Fluoro-[18F]-deoxy-2-D-glucose positron emission tomography (PET/CT) liqBio-MRD performed at the end CIT induction can identify significantly higher risk relapse. The aim this study is to analyze if an interim PET/TC scan could earlier high-risk FL. Methods: We retrospectively identified 121 grade 1–3A FL who had treatment (EOT) PET/CT (after 4 cycles CIT) between 2012 2022. were analyzed using Deauville score (DS). Interim cell free DNA (cfDNA) was available in 15 patients, so we measure MRD by NGS (Jiménez-Ubieto 2023). Results: Most treated R-CHOP (n = 94; 78%) or rituximab-bendamustine 24; 20%). Rituximab maintenance (RM) used 87%. Median follow-up 34 months (3–115). A total (28%) relapsed, 21 (17.5%) within 24 after (POD24). Histological transformation (HT) rate 2.5%. EOT CR 81.5%. PET/CTEOT predictive relapse, 2-years PFS 47% PET/CTEOT(+) vs. 89% PET/CTEOT(-) (p < .001).On iPET/CT, 41 (34%) PET/CT(+).The estimated 5 year-PFS 72% negative iPET/CT versus 29% those positive 0.001) (Figure 1a). POD24 found 34% 7.6% iPET/CT(+) (-)respectively, 0.001; HR 7.89). iPET/CT(-) presented value 94% for POD24. Additionally, 78 93 MR not relevant predict (2-year 93.5%/85.7% 91.3%/87.5%, respectively) 1b). Notwithstanding, EOTPET/CT(+) clear impact 0.05). Additionally SUVmax >3,7 HT, regardless being (6-year TFS 81.9% 100%). trackable mutations 14 cfDNA analysis (93%). 4/14 relapsed median 8.5 months. 3/4 relapsing (+) all non-relapsing test .001). Interestingly, 10 2 have (mesenteric masses). biopsy excluded lymphoma, confirming false PET/CT. Encore Abstract - previously submitted EHA 2023 Keywords: Indolent non-Hodgkin Liquid biopsy, PET-CT No conflicts interests pertinent abstract.