Next-Generation Sequencing-Based Monitoring of Circulating Tumor DNA Reveals Clonotypic Heterogeneity in Untreated PTCL

Peripheral T-cell lymphomas (PTCL) have marked biologic and clinical heterogeneity, which confounds treatment decisions. Advances in circulating tumor DNA (ctDNA) assays employing next generation sequencing (NGS) has improved the detection of molecular relapse and driver mutations in diffuse large B-cell lymphoma, and highlight the potential utility of ctDNA across lymphomas. We investigated NGS-based monitoring of T-cell receptor (TCR) sequences in PTCL patients undergoing frontline treatment (NCT00001337). Of 45 patients, 34 (76%) had tumor-specific clonotypes of the TCR β or ɣ genes identified, which included 18 (86%) from baseline tissue and 16 (67%) from baseline serum. Twenty-five (74%) patients had both TCRβ and TCRɣ clonotypes, 23 (68%) patients had more than one TCRɣ clonotype, and 4 (9%) had multiple TCRβ or TCRɣ clonotypes, demonstrating significant intra-patient clonotypic heterogeneity. Among 24 patients with available serial serum samples during treatment, 9 (38%) cleared ctDNA after 2 cycles of therapy, and 11 (46%) patients had detectable ctDNA at the end of treatment. Patients with detectable ctDNA after therapy showed a trend towards worse survival. Notably, two patients with persistently detectable ctDNA after therapy remain in remission with 10-years of follow-up. Clonotypic heterogeneity in tumors and persistence despite long-term remission suggests variability in oncological potential.