Blood & Marrow Transplant Certified Nurse (BMTCN) Practice Exam

The key concept is that disease burden at the time of transplant has the biggest impact on whether the disease will relapse after allogeneic HSCT. If a patient is transplanted with active disease or a high disease burden, there are more malignant cells present for the donor immune system to control, making relapse more likely even with a graft-versus-leukemia effect. Conversely, patients in complete remission or with very low disease burden have less residual disease for the graft to eradicate, so relapse risk tends to be lower.

Age and stem cell source influence other transplant outcomes (tolerance, engraftment, and GVHD risk) but are not as strong a predictor of relapse itself. The presence of graft-versus-host disease can reflect an active graft-versus-leukemia effect and may be associated with lower relapse in some cases, but it is not a reliable standalone predictor of relapse risk across patients.

So, disease stage at transplant best explains variability in relapse risk after allogeneic HSCT.