Liquid biopsy for disease monitoring after anti‐CD19 chimeric antigen receptor T cell in diffuse large B‐cell lymphoma

OBJECTIVES: Chimeric antigen receptor T cells (CARTs) against CD19 antigen represent an effective therapy for relapsed/refractory diffuse large B‐cell lymphoma (rrDLBCL). There is no diagnostic test able to predict which patients with residual disease will relapse from those that will reach a delayed complete response. Positron emission tomography/computed tomography scan (PET‐CT) is characterized by a significant number of false positive results after immunotherapy. Circulating tumor DNA (ctDNA) may be a good‐useful tool to quantify minimal residual disease and for monitoring disease response. METHODS: We present a patient with DLBCL treated with CART cells in which we tested the combined use of ctDNA and PET‐CT scan. RESULTS: Disease reassessment with PET‐CT scan showed a partial remission (3 weeks) and a very good partial remission (2 months). A clinical progression at 3 months was confirmed with PET‐CT scan. Levels of ctDNA progressively decreased and became undetectable. An initial increase in KMT2D p.E4385G variant allele frequency confirmed disease progression. CONCLUSIONS: Our case shows how the complementary use of ctDNA and PET‐CT scan could be a helpful tool in the clinical management of these patients.