Low blood lymphocyte count at 30 days post transplant predicts worse acute GVHD and survival but not relapse in a large retrospective cohort

Multiple reports have shown that low absolute lymphocyte count at day 30 (ALC30) after allogeneic hematopoietic SCT (AHSCT) is associated with higher risk of disease relapse and worse OS. However, these reports included heterogeneous populations with different grafts and GVHD prophylaxis. Therefore, we retrospectively evaluated the association of ALC30 with transplant outcomes in a cohort of 381 consecutive patients who underwent AHSCT between 2005 and 2010 and received T-replete PBSC grafts and Tacrolimus/Mycophenolate combination as GVHD prophylaxis. Median follow-up was 57 months. Lower ALC30 (⩽400 × 10 6 /L) was associated with lower OS and increased nonrelapse mortality (NRM) for the whole cohort as well as for recipients of SD and UD grafts separately. Lower ALC30 was associated with more severe acute GVHD (aGVHD; III–IV) for the entire cohort as well as for the SD and UD groups. No association was found between lower ALC30 and relapse. Pretransplant factors associated with lower ALC30 were: unrelated donors; HLA mismatch; older donors; lower recipient age; and lower CD34+ cell dose. In this large retrospective study, ALC30⩽400 × 10 6 /L was associated with worse OS, increased NRM and severe aGVHD.