Reduced-intensity versus reduced-toxicity myeloablative fludarabine/busulfan-based conditioning regimens for allografted non-Hodgkin lymphoma adult patients: a retrospective study on behalf of the Société Francophone de Greffe de Moelle et de Thérapie Cellulaire.

Background: Fludarabine/busulfan-based conditioning regimens are widely used to perform allogeneic stem-cell transplantation (allo-SCT) in high-risk non-Hodgkin lymphoma (NHL) patients. The impact of the dose intensity of busulfan on outcomes has not been reported yet.

Patients and methods: This was a retrospective with the aim to compare the outcomes of NHL patients who received before allo-SCT a fludarabine/busulfan conditioning regimen, either of reduced intensity (FB2, 2 days of busulfan at 4 mg/kg/day oral or 3.2 mg/kg/day i.v.) (n = 277) or at a myeloablative reduced-toxicity dose (FB3/FB4, 3 or 4 days of busulfan at 4 mg/kg/day oral or 3.2 mg/kg/day i.v.) (n = 101).

Results: In univariate analysis, the 2-year overall survival (FB2 66.5% versus 60.3%, P = 0.33), lymphoma-free survival (FB2 57.9% versus 49.8%, P = 0.26), and non-relapse mortality (FB2 19% versus 21.1%, P = 0.91) were similar between both groups. Cumulative incidence of grade III-IV acute graft versus host disease (GVHD) (FB2 11.2% versus 18%, P = 0.08), extensive chronic GVHD (FB2: 17.3% versus 10.7%, P = 0.18) and 2-year GVHD free-relapse free survival (FB2: 44.4% versus 42.8%, P = 0.38) were also comparable. In multivariate analysis there was a trend for a worse outcome using FB3/FB4 regimens (overall survival: HR 1.47, 95% CI: 0.96-2.24, P = 0.08; lymphoma-free survival: HR: 1.43, 95% CI: 0.99-2.06, P = 0.05; relapse incidence: HR 1.54; 95% CI: 0.96-2.48, P = 0.07). These results were confirmed using a propensity score-matching strategy.

Conclusion: We conclude that reduced toxicity myeloablative conditioning with fludarabine/busulfan does not improve the outcomes compared with reduced-intensity conditioning in adults receiving allo-SCT for NHL.