Fludarabine and 2-Gy TBI is superior to 2Gy TBI as conditioning for HLA-Matched related hematopoietic cell transplantation: A phase III randomized trial

The risks and benefits of adding fludarabine to a 2-Gy total body irradiation (TBI) nonmyeloablative regimen are unknown. For this reason, we conducted a prospective randomized trial comparing 2-Gy TBI alone, or in combination with 90mg/m² fludarabine (FLU/TBI), before transplantation of peripheral blood stem cells from HLA-matched related donors. Eighty-five patients with hematological malignancies were randomized to be conditioned with TBI alone (n=44) or FLU/TBI (n=41). All patients had initial engraftment. Two graft rejections were observed, both in the TBI group. Infection rates, nonrelapse mortality, and graft-versus-host disease (GVHD) were similar between groups. Three-year overall survival was lower in the TBI group (54% versus 65%; hazard ratio [HR], .57; P= .09), with higher incidences of relapse/progression (55% versus 40%; HR, .55; P= .06), relapse-related mortality (37% versus 28%; HR, .53; P= .09), and a lower progression-free survival (36% versus 53%; HR, .56; P= .05). Median donor T cell chimerism levels were significantly lower in the TBI group at days 28 (61% versus 90%; P<.0001) and 84 (68% versus 92%; P<.0001), as was NK cell chimerism on day 28 (75% versus 96%; P= .0005). In conclusion, this randomized trial demonstrates the importance of fludarabine in augmenting the graft-versus-tumor effect by ensuring prompt and durable high-level donor engraftment early after transplantation.