PF312 RESPONSES TO R‐CHOP CHEMOTHERAPY INCORPORATING BIOSIMILAR RITUXIMAB (TRUXIMA ® ) FOR THE FIRST LINE TREATMENT OF DIFFUSE LARGE B‐CELL LYMPHOMA – INITIAL EXPERIENCE AT UNIVERSITY COLLEGE LONDON HOSPITAL

Background: In April 2017 the first biosimilar rituximab (Truxima ® ; NAPP) was approved in the UK for all indications of the reference biologic (MabThera ® ; Roche). The adoption of biosimilars is expected to deliver significant cost savings in the treatment of many conditions. The approval of Truxima ® was based on comprehensive analytical and pre‐clinical testing together with confirmatory clinical trials in advanced follicular lymphoma and rheumatoid arthritis with subsequent extrapolation to all licensed indications of MabThera ® . There is an absence of clinical trial data supporting the use of biosimilar rituximab in other haematological malignancies, including diffuse large B‐cell lymphoma (DLBCL) where the standard of care is R‐CHOP chemo‐immunotherapy. In the clinical trial leading to the approval of MabThera ® for this indication the complete response rate at the end of treatment was 76% in patients who received R‐CHOP compared to 62% in the group who received CHOP alone 1 . Aims: To assess the response to treatment for all patients treated for de novo stage II‐IV DLBCL with R‐CHOP chemo‐immunotherapy including biosimilar rituximab (Truxima ® ). Methods: All patients starting treatment with R‐CHOP for de novo stage II‐IV DLBCL were identified from the electronic chemotherapy prescribing system and the following data collected: baseline demographics, performance status, staging, Revised International Prognostic Index (R‐IPI), brand of rituximab received, number of R‐CHOP cycles received, number of rituximab doses received, CNS prophylaxis received and response to therapy as assessed by end of treatment PET scan. Results: A total of 70 patients have completed treatment with R‐CHOP chemo‐immunotherapy incorporating biosimilar rituximab (Truxima ® ). Patients received a median of 6 cycles of CHOP (range: 1–6) and 6 doses of rituximab (range: 2–8). 58 patients completed treatment exclusively with Truxima ® . 12 patients switched from MabThera ® to Truxima ® during their treatment after a median of 3 doses (range: 1–6). Response rates for the whole cohort of patients were as follows: Complete Response (CR): 51/70 (73%), Partial Response (PR): 11/70 (16%), Progressive Disease (PD): 6/70 (9%). Two patients died before response could be assessed. 4/70 (6%) patients switched from R‐CHOP to R‐GCVP chemo‐immunotherapy after a median of 2 cycles (range: 1–5); all four patients achieved a CR. Summary/Conclusion: In our single‐centre experience the use of biosimilar rituximab (Truxima ® ) does not appear to adversely impact the response rate to R‐CHOP chemo‐immunotherapy in patients with stage II‐IV diffuse large B‐cell lymphoma as assessed by post‐treatment PET scan. Longer term follow‐up in a larger patient group is required to confirm these results.