Prolonged Transfusion-Dependent Temozolomide-Induced Thrombocytopaenia in Glioblastoma: Risk Factors Remain Elusive

Abstract AIMS Temozolomide-induced thrombocytopaenia is well-recognised; clinical-course varies widely. Aims: To identify risk factors for prolonged thrombocytopaenia; improve patient-care; inform trial design. METHOD Glioblastoma (GBM) patients requiring platelet transfusion were identified. (Local policy: transfuse when plt count ≤ 30 x 109/L). Inclusion criteria: First-line-standard-of-care temozolomide-chemo-radiotherapy (TMZ-CRT). Case-notes reviewed demographics, blood-counts, radiotherapy and treatment parameters. Thrombocytopaenia grading: CTCAE V5. Date of onset measured from start TMZ-CRT to date platelets < 100 109/L, first instance ≥ grade 3 thrombocytopaenia. duration: time recovery 100x109/L. RESULTS Between 2017-2021, 69 required transfusion; 68/69 identified on routine monitoring. 49 analysed (6:no CRT; 5:trial study drug; 7:≥ 2nd line treatment; 2:inadequate data). Median age: 59 (range 25-73); 61% female. First incidence during concurrent TMZ-CRT: 27/49 patients; adjuvant TMZ in 22/49 (13/22 following 6-week-TMZ-CRT, 9/22 3-week-TMZ-CRT). In patients, median thrombocytopaenia: 33 days 23-38); 44 20-105; 5 not recovered); number transfusions: 1-2:9 pts; 3-4:6pts; 5-7:3pts; 8-10:7pts; >10:2pts. Of 22 transfused, 8/22 developed ≥G3 post-cycle-2; 19/22 resolved after 1 or 2 transfusions. Thrombocyopaenia was associated with neutropaenia 11% <5 transfusions vs 75% 5. Comparison transfusion-patients did differences any demographic CONCLUSION Risk TMZ-induced thrombocytopenia swiftly-resolving remain elusive. This needs be reflected consent processes design clinical trials.