Impact of single-agent ibrutinib lead-in on tumor burden for TLS prophylaxis. (A) Tumor burden categories for TLS prophylaxis at baseline and after ibrutinib lead-in in the all-treated population. (B) Indication for hospitalization (*) for TLS monitoring and prophylaxis at baseline and after ibrutinib lead-in in the all-treated population. *Defined as patients in high tumor burden category for TLS prophylaxis or patients in medium tumor burden category with creatinine clearance (CrCL) <80 mL/min. Of 28 patients who met the criteria for indication for hospitalization after lead-in, 27 had medium tumor burden and a CrCL of <80 mL/min, and 1 had high tumor burden.