The impact of donor gender on outcome of allogeneic hematopoietic stem cell transplantation for multiple myeloma: reduced relapse risk in female to male transplants.

The impact of the donor gender on outcome in HLA-identical sibling donor hematopoietic stem cell transplantation for multiple myeloma was studied in a retrospective registry study of 1312 patients (476 male to male (M --> M); 334 female to male (F --> M); 258 male to female (M --> F); 244 female to female (F --> F) reported to the European Group for Blood and Marrow Transplantation (EBMT). The best overall survival (OS) from the time of transplantation was found in F --> F (median 41 months) with no significant difference between other groups (median 25 months in M --> M, 18 months in F --> M, 19 months in M --> F) despite a significantly higher nonrelapse mortality in F --> M. This was due to a significantly lower relapse rate (REL) in F --> M compared to all other groups. Before 1994, OS was poorer in F --> M than in M --> M, which improved to similarity from 1994 onwards (median 29 months in M --> M and 25 months in F --> M). The reduced REL contributed to this improvement in F --> M indicting a gender-specific graft vs myeloma effect. Therefore, a female donor is as good as a male one for male patients, while for female patients gender disparity is a negative factor for outcome.