Clonal evolution in relapsed and refractory diffuse large B-cell lymphoma is characterized by high dynamics of subclones

// Thomas Melchardt 1, 2, 3, * , Clemens Hufnagl 1, 2, 3, * , David M. Weinstock 4 , Nadja Kopp 4 , Daniel Neureiter 5 , Wolfgang Trankenschuh 5 , Hubert Hackl 6 , Lukas Weiss 1, 2, 3 , Gabriel Rinnerthaler 1, 2, 3 , Tanja N. Hartmann 1, 2, 3 , Richard Greil 1, 2, 3 Oliver Weigert 7, 8 , Alexander Egle 1, 2, 3 1 Third Medical Department at The Paracelsus Medical University Salzburg, Salzburg, Austria 2 Salzburg Cancer Research Institute (SCRI), Salzburg, Austria 3 Cancer Cluster Salzburg (CCS), Salzburg, Austria 4 Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, USA 5 Institute of Pathology, Paracelsus Medical University Salzburg, Salzburg, Austria 6 Division of Bioinformatics, Biocenter, Medical University of Innsbruck, Innsbruck, Austria 7 University Hospital of The Ludwig-Maximilians-University Munich, Medical Department III, Laboratory for Experimental Leukemia and Lymphoma Research (ELLF), Munich, Germany 8 German Cancer Consortium (DKTK) and German Cancer Research Center (DKFZ), Heidelberg, Germany * These authors have contributed equally to this work Correspondence to: Alexander Egle, email: a.egle@salk.at Keywords: DLBCL, clonal evolution, TP53, tumor heterogeneity, subclonal selection Received: November 18, 2015 Accepted: May 22, 2016 Published: June 06, 2016 ABSTRACT Little information is available about the role of certain mutations for clonal evolution and the clinical outcome during relapse in diffuse large B-cell lymphoma (DLBCL). Therefore, we analyzed formalin-fixed-paraffin-embedded tumor samples from first diagnosis, relapsed or refractory disease from 28 patients using next-generation sequencing of the exons of 104 coding genes. Non-synonymous mutations were present in 74 of the 104 genes tested. Primary tumor samples showed a median of 8 non-synonymous mutations (range: 0-24) with the used gene set. Lower numbers of non-synonymous mutations in the primary tumor were associated with a better median OS compared with higher numbers (28 versus 15 months, p=0.031). We observed three patterns of clonal evolution during relapse of disease: large global change, subclonal selection and no or minimal change possibly suggesting preprogrammed resistance. We conclude that targeted re-sequencing is a feasible and informative approach to characterize the molecular pattern of relapse and it creates novel insights into the role of dynamics of individual genes.