Impact of pre-transplant bone marrow plasma cell percentage on post-transplant response and survival in newly diagnosed multiple myeloma.

We evaluated 1070 patients with newly diagnosed multiple myeloma, who completed a single line of induction therapy followed by autologous stem cell transplantation. Patients with pre-transplant <5% BMPC had a threefold likelihood of achieving stringent complete response (sCR) after transplant compared to those with BMPC ≥5% (45.6% vs. 16.3%; p < 0.0001). The median progression-free survival and overall survival from transplant for patients with pre-transplant BMPC <5% and ≥5% was 30.8 and 115.2 months compared to 20.8 and 74.1 months, respectively (p < 0.0001 for both comparisons). The effect of pre-transplant BMPC was most pronounced in patients achieving complete response or very good partial response after transplant. In conclusion, pre-transplant BMPC <5% is an important prognostic marker of long-term survival after transplant and should be routinely incorporated into pre-transplant risk stratification.