Early lymphocyte recovery predicts clinical outcome after HSCT with mycophenolate mofetil prophylaxis in the Japanese population.

Immune reconstitution affects clinical outcomes after allogeneic hematopoietic stem cell transplantation (HSCT), and it has been suggested that lymphocyte recovery affects survival after HSCT. However, few studies have examined lymphocyte recovery in Asian patients who received mycophenolate mofetil (MMF) prophylaxis for graft-versus-host disease. We retrospectively evaluated early lymphocyte recovery after HSCT among Japanese adults who received MMF prophylaxis. Patients were divided into two groups according to their median absolute lymphocyte count (ALC) on day 28 after HSCT as follows: the "low ALC group" (≤ 0.22 × 10 ⁹  cells/L) and the "high ALC group" (> 0.22 × 10 ⁹  cells/L). With a median follow-up of 317 days, the high ALC group showed significantly better overall survival than the low ALC group (at 1 year: 62 vs. 46%, P = 0.02). The high ALC group also tended to have better non-relapse mortality than the low ALC group (at 1 year: 13 vs. 23%, P = 0.08). There was no significant difference in relapse rate between the high and low ALC groups (at 1 year: 29 vs. 35%, P = 0.2). We conclude that among Japanese patients who received MMF prophylaxis, ALC on day 28 after HSCT was effective in predicting overall survival and non-relapse mortality.