Characteristics of oral mucositis in patients undergoing haploidentical stem cell transplantation with posttransplant cyclophosphamide: marked difference between busulfan and melphalan regimens.

Objective: This study was performed to examine the effects of conditioning regimens on oral mucositis in haploidentical (haplo) donor hematopoietic stem cell transplantation (HSCT) with posttransplant cyclophosphamide (PTCy).

Methods: Thirty consecutive patients (male, 23; female, 7; 18-68 years, median, 59 years) undergoing haplo-HSCT with PTCy using one of three conditioning regimens-reduced intensity conditioning (RIC)-melphalan (Mel); RIC-Busulfan (Bu); and myeloablative conditioning (MAC)-Bu-were enrolled in this study. Data on the WHO grade of oral mucositis (day - 7 to + 20) were collected retrospectively. The incidences of ulcerative and severe mucositis (Grade 2-4 and Grade 3-4, respectively) were compared between the three groups.

Results: Ulcerative mucositis occurred in 0% (0/10) of patients in the RIC-Mel group, 57.1% (4/7) in the RIC-Bu group, and 100% (13/13) in the MAC-Bu group. The differences between the RIC-Mel and RIC-Bu groups and between the RIC-Bu and MAC-Bu groups were significant (all P < 0.05). Severe mucositis occurred in 57.1% (4/7) of patients in the RIC-Bu group and 100% (13/13) of patients in the MAC-Bu group, and the difference was significant (P < 0.05). The rates of ulcerative mucositis (≥ grade 2) and of severe mucositis (≥ grade 3) were significantly higher in the MAC-Bu group than the RIC-Bu group on days 10, 13, 15, and 16 and on days 10, 14, 15, and 16, respectively (all P < 0.05).

Conclusions: The risk of oral mucositis in patients undergoing haplo-HSCT with PTCy is highest with the MAC-Bu conditioning regimen, followed by RIC-Bu, and lowest with RIC-Mel.