Allogeneic transplants in follicular lymphoma: higher risk of disease progression after reduced-intensity compared to myeloablative conditioning.

Reduced-intensity conditioning (RIC) regimens have been increasingly used for allogeneic hematopoietic stem cell transplantation (HSCT) in follicular lymphoma (FL). We compared traditional myeloablative conditioning regimens to RIC in FL. Outcomes of HLA-identical sibling HSCT for FL in 208 recipients reported to the Center for International Blood and Marrow Transplant Research (CIBMTR) between 1997 and 2002 were studied. Conditioning regimens were categorized as myeloablative (N = 120) or RIC (N = 88). Use of RIC regimens increased from <10% of transplants in 1997 to >80% in 2002 signaling a major shift in practice. Patients receiving RIC were older and had a longer interval from diagnosis to transplant. These differences did not correlate with outcomes. Median follow-up of survivors was 50 months (4-96 months) after myeloablative conditioning versus 35 months (4-82 months) after RIC (P < .001). At 3 years, overall survival (OS) for the myeloablative and RIC cohorts were 71 (63%-79%) and 62 (51%-72%; P = .15) and progression free survival (PFS), 67 (58%-75%) and 55 (44%-65%; P = .07), respectively. Lower Karnofsky performance score (KPS) and resistance to chemotherapy were associated with higher treatment-related mortality (TRM) and lower OS and PFS. On multivariate analysis, an increased risk of lymphoma progression after RIC was observed (relative risk = 2.97, P = .04). RIC has become the de facto standard in allogeneic HSCT for FL, and appears to result in similar long-term outcomes. Although disease-free survival (DPS) is similar compared to myeloablative conditioning, an increased risk of late disease progression after RIC is concerning.