Outcomes after allogeneic hematopoietic cell transplantation with nonmyeloablative or myeloablative conditioning regimens for treatment of lymphoma and chronic lymphocytic leukemia.

Allogeneic conventional hematopoietic cell transplantation (HCT) can be curative treatment for lymphoid malignancies, but it has been characterized by high nonrelapse mortality (NRM). Here, we compared outcomes among patients with lymphoma or chronic lymphocytic leukemia given either nonmyeloablative (n = 152) or myeloablative (n = 68) conditioning. Outcomes were stratified by the HCT-specific comorbidity index. Patients in the nonmyeloablative group were older, had more previous treatment and more comorbidities, more frequently had unrelated donors, and more often had malignancy in remission compared with patients in the myeloablative group. Patients with indolent versus aggressive malignancies were equally distributed among both cohorts. After HCT, patients without comorbidities both in the nonmyeloablative and myeloablative cohorts had comparable NRM (P = .74), overall survival (P = .75), and progression-free survival (P = .40). No significant differences were observed (P = .91, P = .89, and P = .40, respectively) after adjustment for pretransplantation variables. Patients with comorbidities experienced lower NRM (P = .009) and better survival (P = .04) after nonmyeloablative conditioning. These differences became more significant (P < .001 and .007, respectively) after adjustment for other variables. Further, nonmyeloablative patients with comorbidities had favorable adjusted progression-free survival (P = .01). Patients without comorbidities could be enrolled in prospective randomized studies comparing different conditioning intensities. Younger patients with comorbidities might benefit from reduced conditioning intensity.