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One-year real-life targeted next generation sequencing for lymphoma diagnosis: study of patients from the French Lymphoma Network in Rhône-Alpes
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International audience. Introduction: During last years, NGS studies, performed on patient cohorts, provided new insights into genomic characterization of lym-phoma landscape. However, to date, the impact of NGS data on the daily diagnosis practice has not been reported yet. We reported herethe clinical impact of targeted next generation sequencing (TNGS) in lymphoma diagnosis after expert histological review in Rhône-Alpes(France).Materials and Methods: In France, difficult lymphoma diagnoses are systematically reviewed, in real time, by histological experts throughthe Lymphopath Network. To increase diagnosis accuracy, we used a TNGS approach to identify pathogenic genomic variants that couldbe helpful in lymphoma diagnosis. From 12/2017 to 12/2018, we performed TNGS on tumour biopsy (FFPE or frozen) samples fromprimary CNS lymphomas and lymphoma of difficult diagnosis, that were histologically reviewed in Lyon Pathology Department. Becausea difficult diagnosis implies a doubt between several entities, benign conditions were classified with the lymphoma they were suspectof. We used a panel of 46 genes, chosen after an extensive literature review of NGS lymphoma studies. Impact of TNGS data on histologi-cal diagnosis was classified as follows: confirms diagnosis; changes diagnosis; does not help. The term concordance was defined as theaddition of “confirms” and “does not help”. To evaluate the potential impact on patient care, modifications into the final diagnosis weredivided into major and minor changes according to the ESMO guidelines.Results: Among the 230 patients and after expert histological reviewing, 20 (8.6%) were suspected of primary CNS lymphoma(PCNSL), 47 (20.3%) of large B-cell lymphoma (LBCL), 90 (38.7%) of small B-cell lymphoma (SBCL), 6 (2.6%) of Hodgkin lymphoma (HL),56 (23.9%) of TFH T-cell lymphoma and 12 (5.7%) of non-TFH T-cell lymphoma. After TNGS, the overall concordance rate was 85.3%, from76.9% in non-TFH T-cell lymphoma to 100% in PCNSL and HL. TNGS confirmed the histological diagnosis in 122 cases (53%), changed thediagnosis in 33 cases (14.3%) and did not bring any help in 75 cases (32.6%, from 10% in PCNSL to 100% in HL). Modifications betweeninitial and final diagnosis had an impact on patient care for 11.3% of cases (26/230). Diagnosis modifications occurred in all types of lym-phoma except PCNSL and HL, and the highest modification rate was in TFH and in non-TFH T-cell lymphoma, 21.8% and 23.1%, respec-tively. In about 2/3rd (65,4%) of the cases of changes, reclassification of the lymphoma subtype had a direct therapeutic impact, whereasonly 12.1% of the changes were a reclassification between benign and malignant.Conclusions: This study highlights that TNGS may directly contribute to a more accurate diagnosis in lymphoma patients and improve theirclinical management in routine. One current limitation is the lack of sensitivity of TNGS in lymphoma with low tumour infiltration. Keywords: B-cell lymphoma; molecular genetics; T-cell lymphoma (TCL).
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