Can flow cytometry of bone marrow aspirate predict outcome of patients with diffuse large B cell lymphoma? A retrospective single centre study.

Bone marrow (BM) trephine biopsy is a part of routine staging of patients with newly diagnosed diffuse large B cell lymphoma (DLBCL). The significance of lymphoid monoclonal population on flow cytometry (FC) of the BM aspirate in the presence of negative BM histology has not been clarified. In this study, we assessed the clinical role of positive FC in predicting outcome of patients with DLBCL and a negative BM histology. We retrospectively analysed 101 patients diagnosed with DLBCL at a single institution between years 1994-2003. Three groups of patients were compared: patients with histologic involvement of the BM (BM+), patients with no histologic involvement of the BM but with positive FC (BM-FC+) and patients with neither histologic or FC evidence of BM involvement (BM-FC-). The BM+ group included 13 patients (13%). The BM-FC+ group 16 patients (16%), and the BM-FC-included 72 patients (71%). Median age of the cohort was 67 years. Disease stage and International Prognostic Index score were significantly higher in the BM+ and BM-FC+ groups compared with the BM-FC- group. Median overall survival (OS) for the BM-FC-, BM-FC+ and BM + groups were 4.6, 2.2 and 0.9 years, respectively. Median progression free survival (PFS) for the BM-FC-, BM-FC+ and BM+ groups were 3.2, 1.4 and 0.6 years, respectively (p=0.01 for both analysis). In multivariable Cox regression models adjusting for age, sex, stage and International Prognostic Index, there was no significant differences in OS or PFS between the BM-FC+ and BM-FC- groups. In conclusion, positive FC in the setting of negative BM histology at diagnosis did not significantly affect OS or PFS.