MKI67 and mantle cell lymphoma: The combination of ibrutinib and rituximab was studied in a phase 2 trial enrolling 50 patients with r/r MCL and demonstrated an ORR of 88% (44%) with more favorable response rate noted in patients with Ki67 < 50% (ORR 100%, 54% CR) compared with high-risk patients with Ki67 ≥ 50% (ORR 50%, 17% CR) [16].