Female Sex Is Associated with Improved Long-Term Survival Following Allogeneic Hematopoietic Stem Cell Transplantation

ABSTRACT Life expectancy for long-term survivors of allogeneic hematopoietic stem cell transplantation (alloHSCT), defined as those living ≥5 years post-transplantation, is significantly lower compared with that of the age-matched general population despite a relatively low primary disease relapse rate at >2 years post-transplantation. Among several factors, patient sex is increasingly recognized as a prognostic indicator of long-term survival. We examined the influence of patient sex and donor-recipient sex matching on overall survival (OS) in a landmark analysis of long-term survivors. Using our institutional database supplemented with individual patient record review, we retrospectively investigated the relative influence of recipient sex and donor-recipient sex matching on outcomes of long-term survivors of alloHSCT between 1994 and 2014. Over this 20-year period, 247 met inclusion criteria for analysis; males and females had similar demographic and treatment characteristics. However, significantly more deaths after the 5-year landmark occurred in male recipients. Interestingly, donor sex did not have a significant impact on OS in multivariate analysis, and differences in OS of donor-recipient sex pairs was driven by recipient sex. In addition to recipient sex, only chronic graft-versus-host disease (cGVHD) retained significance as a covariate with an impact on OS in multivariate analysis. Men experienced slightly higher, but statistically nonsignificant, rates and increased severity of cGVHD, and had higher cGVHD-related mortality compared with females. In this long-term survival analysis of adult alloHSCT recipients, one of the only to include follow-up to 15 years, our results show that women survive significantly longer than men irrespective of their age at transplantation. This outcome is independent of other common pretransplantation prognostic indicators, such as donor sex or performance status at transplantation. The inferior survival in males is consistent with survival outcomes described in the transplantation literature. Increasing evidence suggests a biological basis for long-term sex-determined outcomes, possibly owing to differing rates or severity of cGVHD or sustained alloimmune tolerance in females. Larger studies are warranted to validate these retrospective clinical results.