Patients were included according to the French marketing authorization in 2016 (i.e. patients with relapsed or refractory CLL or to previously untreated CLL patients with deletion 17p and/or tumor protein p53 mutations unsuitable for chemoimmunotherapy) and could have initiated ibrutinib more than 30 days prior their enrolment in the study (i.e. retrospective patients) or between 30 days before and 14 days after their enrolment (i.e. prospective patients). Here, TP53 is linked to B-cell chronic lymphocytic leukemia.