High Ki-67 expression in involved bone marrow predicts worse clinical outcome in diffuse large B cell lymphoma patients treated with R-CHOP therapy.

Approximately 10-25 % of patients with diffuse large B cell lymphoma (DLBCL) at the time of diagnosis exhibit bone marrow involvement (BMI). After introduction of rituximab, immunohistochemistry (IHC) markers lost to prognostic value in DLBCL patients. However, the specimens used have mainly been diagnostic tissues, not bone marrow (BM). It would thus be useful to determine the prognostic value of specific IHC markers of pathologic BM in DLBCL patients with BMI in the rituximab era. In the present study, a total of 580 DLBCL patients were analyzed 67 of whom had BMI. CD10, Bcl-6, MUM-1, Bcl-6 and Ki-67 dyeing on pathologic BM were applied. Bcl-2 positivity was more frequent in discordant BMI (P = 0.039) and high Ki-67 expression was more frequent in concordant BMI (P = 0.016). High Ki-67 expression independently predicted poor prognosis between the negative BMI group and each of the following BMI-positive groups: entire BMI (PFS, P < 0.001; OS, P < 0.001), concordant BMI (PFS, P = 0.024; OS, P = 0.007), and discordant BMI (PFS, P = 0.033; OS, P = 0.026). We found that Ki-67 expression in pathologic BM is a novel significant prognostic parameter of worse prognosis in DLBCL patients with BMI in the rituximab era.