Reduced-intensity preparative regimen and allogeneic stem cell transplantation for advanced solid tumors.

In this prospective multicenter program, we investigated allogeneic stem cell transplantation (ASCT) from HLA-identical siblings following reduced-intensity conditioning (RIC) regimen for patients with refractory metastatic solid tumors (STs). Fifty-seven patients, of whom 39 had a progressive disease (PD) at time of ASCT, received an RIC ASCT combining fludarabine, antithymocyte globulin (ATG), and busulfan. Patients were analyzed in terms of engraftment, transplant-related mortality (TRM), disease response, and outcome. In this setting, RIC was associated with rapid engraftment and low overall TRM (9% [95% confidence interval (CI), 1%-16%]). The cumulative incidence of objective responses (ORs) reached 14% (95% CI, 6%-30%) with this being significantly higher in patients without PD (44% [95% CI, 21%-67%] versus 0; P <.0001) at time of ASCT. Achievement of OR translated into a significantly better overall survival (OS). In multivariate analysis, OS was significantly influenced by disease status at time of ASCT (odds ratio, 4.88; P <.001) and chronic graft-versus-host disease (GVHD) occurrence (odds ratio, 2.86; P <.01). Overall, these results showed that OR can occur after RIC ASCT for resistant ST with a relatively low TRM and potential benefit especially in patients with slowly progressive disease. Further studies are warranted in patients with less advanced ST.