Clinical significance of plasmacytosis in the day+14 bone marrow of patients with acute myeloid leukaemia undergoing induction chemotherapy

Background: The design of chemotherapy-induction regimens for acute myeloid leukaemia (AML) is directed towards the early elimination of bone marrow (BM) leukaemic blast cells (LBCs). Patients with AML after induction show LBC reduction in a hypoplastic BM and also demonstrate a varying number of residual BM plasma cells (PCs). Aim: To relate PC number to several blood and BM parameters as well as clinical features such as infection and survival. Methods: On the 14th day after the start of chemotherapy (D+14) BM samples were examined for residual PCs in 60 adult (⩾15 years) patients undergoing AML-induction chemotherapy, and the proportion of PCs was related to blood and BM parameters including French–American–British (FAB) subtype, other inflammatory cells, antecedent infection, attainment of complete remission and 36-month survival. Results: Median PC proportion of 11.3% (range 0.1–48.7%) in D+14 BM aspirates and 10.7% (0.6–41%) in trephine biopsies was observed. Their number showed a direct relationship with residual BM lymphocytes (r = 0.368; p = 0.025). Higher numbers of residual PCs also reflected the presence of infection before diagnosis and coincident with treatment (p = 0.039). Although we could not demonstrate an association between PC numbers and 36-month survival, PC numbers were significantly higher in patients with residual leukaemia at D>14 (p = 0.007). Conclusion: D+14 BM PC number reflects the effectiveness of induction chemotherapy and the presence of antecedent inflammation or infection.