Circulating tumor DNA to predict response and resistance by anti-PD-1 therapy in Chinese relapsed/refractory classic Hodgkin lymphoma.

Abstract

7534 Background: A large fraction of patients with relapsed/refractory (r/r) Classic Hodgkin Lymphoma (cHL) enjoy a beneficial response induced by PD-1. However, no reliable predictive biomarkers for response or resistance are available. Sintilimab, an anti-PD1 agent, has recently demonstrated efficacy and safety in a multi-center, single-arm, phase II study of Chinese patients with r/r cHL (ORIENT-1). The predictive value of circulating tumor DNA (ctDNA) in longitudinal samples from patients in ORIENT-1 was investigated. Methods: A total of 192 plasma samples were collected from 75 patients prior to treatment and during therapy. After ctDNA extraction next-generation sequencing (NGS) was performed using the HiSeq Sequencing System to assess either a 619 or 659 gene panels at an average sequencing depth of 1260×. The panels include frequently mutated genes in cHL and other hematological malignancies. DNA from paired granulocytes was sequenced as presumptive germline control. Results: The genomic profiling of baseline ctDNA revealed a mean allele mutation frequency of 5.47%. Among the most frequently mutated genes in these cHL patients, PCLO and LRP1B are likely unique to Chinese r/r cHL patients. Truncating mutation of B2M, DNMT3, TNFRSF14 and KDM2B were found in patients with acquired resistance, of which TNFRSF14 and KDM2B have not been reported before and need to be confirmed in further study. The baseline ctDNA level was significantly different between objective response group (CR+PR, n = 41, median = 8.72) and non-responder group (SD+PD, n = 9, median = 2.9) ( p= 0.0070) Patients with ctDNA high achieved response earlier than others ( p< 0.05). A drop of 40% in ctDNA after three cycles of therapy confirmed as best cut-off to predict progression associated with clinical benefit, demonstrating 100% specificity. Patients with ctDNA drop ≥40% achieved response significantly earlier (median = 71 days) than others (median = 216 days, p= 0.0074). Conclusions: Our study demonstrated that ctDNA could serve as valuable biomarker for prediction of response or resistance to anti-PD1 immunotherapy.