Low‐ versus standard‐dose post‐transplant cyclophosphamide as GVHD prophylaxis for haploidentical transplantation.

Summary: Haploidentical haematopoietic cell transplantation (haplo‐HCT) using post‐transplant cyclophosphamide (PTCY) as graft‐versus‐host disease (GVHD) prophylaxis is the standard of care for various haematological malignancies. The original PTCY dose after haplo‐HCT was 100 mg/kg, but no dose‐finding studies have been performed to identify the optimal dose. We performed a retrospective analysis to compare standard‐dose PTCY (100 mg/kg) with reduced‐dose PTCY (80 mg/kg): 969 in the standard‐dose group and 538 in the reduced‐dose group. As there was a significant difference between the two groups regarding patient and transplant characteristics, we performed propensity score (PS) matching. After PS matching, 425 patients in each group were included. The probabilities of 2‐year OS were 55.9% in the standard‐dose group and 47.0% in the reduced‐dose group (p = 0.36). The cumulative incidences of 2‐year non‐relapse mortality were 21.3% in the standard‐dose group and 20.5% in the reduced‐dose group (p = 0.55). There was no significant difference in the incidence of acute (grade II–IV 29.2% [95% CI, 24.9–33.6] vs. 25.3% [95% CI, 21.3–29.6]; grade III–IV 7.3% [95% CI, 5.1–10.0] vs. 6.6% [95% CI, 4.5–9.3]) or chronic GVHD. In conclusion, reduced‐ and standard‐dose PTCY were comparable in terms of major clinical outcomes. [ABSTRACT FROM AUTHOR]