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.