Adverse event burden in older patients with CLL receiving bendamustine plus rituximab or ibrutinib regimens: Alliance A041202

Ibrutinib has superior progression-free survival compared with bendamustine plus rituximab (BR) in older CLL patients, however, differences in treatment duration, six monthly BR cycles versus continuous ibrutinib, complicate adverse event (AE) comparisons. We introduce the AE burden score ( AE sc ) to compare AEs, calculated for each patient by summing over products of reporting period length and grade for each all-cause grade 1–4 AE and dividing by the length of time over which AEs are assessed. A total of 176 patients received BR and 361 ibrutinib alone or with six cycles of rituximab. At 38 months median follow-up, 64% remained on ibrutinib. Median AE sc was higher with BR versus ibrutinib in the first six cycles (7.2 versus 4.9, p