Quantifying Benefit of Autologous Transplantation for Relapsed Follicular Lymphoma Patients via Instrumental Variable Analysis

• Relapsed follicular lymphoma patients were studied at 3 tertiary centers.
• ASCT at relapse 1 or 2 was used for 58%, 5%, and 7% patients at the 3 centers.
• Superior survival was found at the center with more frequent use of ASCT.
• An instrumental variable analysis (IVA) used center as the instrumental variable.
• Multivariate and IVA demonstrated ASCT at relapse 1 or 2 improved OS for FL patients.

The role of autologous stem cell transplantation (ASCT) in patients with relapsed follicular lymphoma (FL) remains controversial because of a lack of proven overall survival (OS) benefit versus nontransplant strategies. We conducted a comparative effectiveness research study involving 3 tertiary Canadian cancer centers to determine whether the ASCT-based approach used at 1 center improved OS relative to non-ASCT approaches used at the other centers. Of 1082 consecutive patients aged 18 to 60 years and diagnosed with FL from 2001 to 2010, the study population included 355 patients who experienced relapse from chemotherapy (center A = 96, center B = 84, center C = 175). Data were analyzed according to the instrumental variable of treatment center to control for confounding factors. The frequency of using ASCT at first or second relapse was significantly different between the centers (A = 58%, B = 7%, C = 5%, P < .001). With a median follow-up of 69.1 months, the actuarial 5-year OS rates after first chemotherapy relapse were 89%, 60%, and 60% for centers A, B, and C respectively (log rank P < .0001). Based on instrumental variable analysis, the use of ASCT at relapse 1 or 2 significantly decreased the risk of death from first relapse (HR .127, P = .004) and from initial diagnosis (HR .116, P = .004). In conclusion, for FL patients who relapse after chemotherapy, these results strongly support more frequent use of ASCT at first or second relapse.