Reduced-intensity conditioning reduces the risk of severe infections after allogeneic peripheral blood stem cell transplantation.

We compared the occurrence of severe infections following 71 reduced-intensity conditioning (RIC) allogeneic peripheral blood stem cell transplants (PBSCT) and 123 standard myeloablative PBSCT (MINI and STAND groups, respectively) from HLA-identical siblings. The probability of 1-year infection-related mortality (IRM) was 19% in the STAND group and 10% in the MINI group (log-rank, P = 0.3). On multivariate analysis the only significant variable associated with a higher risk of IRM was the development of moderate-to-severe GVHD (P = 0.005). The probability of developing CMV infection was 39% in the STAND group and 21% in the MINI group (P = 0.03) (43% and 21%, respectively, in seropositive donor/recipient pairs, P = 0.01), and the probability of developing CMV disease was 9.5% and 1%, respectively (P = 0.05) (11% and 1%, respectively, in seropositive donor/recipient pairs, P = 0.03). Multivariate analysis of CMV infection identified four variables associated with a higher risk: CMV positive serostatus (P = 0.05), STAND transplant group (P = 0.02), the development of moderate-to-severe GVHD (P < 0.001) and a dose of CD34(+) cells infused below 6 x 10(6)/kg (P = 0.01). Invasive fungal infections and pneumonias of unknown origin did not differ between groups, and neither did other severe non-CMV viral infections and bacterial infections. Our results suggest that RIC allogeneic PBSCT may decrease the risk of dying from an opportunistic infection and reduces the occurrence of CMV infection and disease. Overall, the development of GVHD (acute or chronic) is an important risk factor for these complications. Other infections continue to pose a significant threat to recipients of RIC allografts, stressing that prophylactic and supportive measures are an important aspect in their care.