CIRCULATING TUMOR DNA MEASUREMENT AND TOTAL METABOLIC TUMOR VOLUME BY PET/CT AS PARAMETERS FOR TUMOR BURDEN AND CLINICAL RESPONSE IN DIFFUSE LARGE B‐CELL LYMPHOMA

Introduction: Circulating tumor DNA (ctDNA) derives from cell-free (cfDNA) and has been described as a diagnostic prognostic test in diffuse large B cell lymphoma (DLBCL). Its quantification may be used surrogate of burden. Besides, total metabolic volume (TMTV) measured by PET/CT can quantify Methods: We followed prospectively 18 patients with DLBCL collected cfDNA before treatment 2 months after end chemotherapy. For ctDNA evaluation, extraction, we next-generation sequencing (NGS) panel 11 genes selected relevance (KMT2D, TP53, CREBBP, LRP1B, PIM1, MYD88, PCLO, B2M, CARD11, CD79B HIST1H1E). As previously demonstrated, quantitative levels were haploid genome equivalents per milliliter (hGE/mL), determined the product concentration mean allele fraction somatic mutations. TMTV was calculated at diagnosis treatment. Results: The median patients’ follow-up 24.9 (4.6–46.1). Median age 59 y (24–84), 55% female mostly white (78%). Seven (39%) primary gastric presentation, 5 localized advanced diseases, according to Lugano TGI classification. Among non-gastric (n = 11), had bulky disease. IPI-NCCN low-intermediate (LI-IPI) high-intermediate (HI-IPI) 33% patients. After treatment, 14 complete remission (CR) RCHOP. There 4 deaths. 9 measurement (DNA1) higher value then (DNA2). Within this group, 8 CR other case died response assessment. In hand, DNA2 than DNA1 patients, these without relapse so far. 1 early 3 refractory One patient similar results (patient CR). Higher common HI-IPI (4 pts, 67%). correlated (Spearman ρ 0.69 p 0.03). However, therapy didn’t correlate (ρ 0.34 0.25). Conclusions: With small sample size limited NGS painel, able demonstrate correlation between hGE/mL clinical response. Patients decrease compared remission. occurred also response, which could point low specificity. showed good disease measurement. To best our knowledge, is first cohort South America evaluation for burden research funded by: Laboratório Fleury Fundação de Amparo à pesquisa do estado São Paulo (FAPESP) Keywords: biomarkers, liquid biopsy, PET-CT No conflicts interests pertinent abstract.