Autologous Stem Cell Transplantation (ASCT) for the Treatment of Patients with Waldenstrom’s Macroglobulinemia / Lymphoplasmacytic Lymphoma (WM/LPL). a Risk Factor Analysis By the European Society for Blood and Marrow Transplantation (EBMT) Lymphoma Working Party

WM/LPL is a rare distinct indolent lymphoma and the optimal management of the disease remains a major challenge. Combination therapies with old and novel agents have markedly improved the response rates and the quality of response but still the CR rates remain low and so far there is no cure. The role and timing of ASCT in the management of patients with WM/LPL has not been well established. The aim of the present study was to investigate the outcome of ASCT in early vs late WM/LPL.

Methods: Eligible for this retrospective study were all patients who had a first ASCT for WM/LPL between 1995 and 2011 and were registered with the EBMT database. Baseline patient, disease, and transplant data were collected from MED-A forms. Statistical analysis used log rank tests to assess the impact of baseline characteristics on survival endpoints. Overall survival (OS) and disease-free survival (DFS) was estimated from the time of ASCT using Kaplan-Meier product-limit estimates. Curves of cumulative of non-relapse mortality (NRM) and incidence of relapse (IR) were compared by Gray’s test in a competing risk framework.

Results: Altogether 615 patients fulfilling the inclusion criteria were identified in the database. The median age at ASCT was 53 years (range 19-76), and 428 patients (70%) were male. The median time from diagnosis to ASCT was 19 months (interquartile range: 10-51 months). 537 patients (71%) underwent ASCT after 2002. Disease status at ASCT was first partial (PR1), very good partial (VGPR1) or complete remission (CR1) in 325 patients, whilst 176 patients were autografted in second, third or later response, and 47 patients (4%) had primary refractory or progressive disease at ASCT. High-dose therapy was TBI-based in 82 patients (14%), and stem cell source was from peripheral blood in 598 patients (97%).

With a median follow-up of surviving patients of 53 months, the 5-year OS was 65%, DFS was 46%, IR was 47% and NRM was 7%. IR was significantly lower in patients receiving ASCT in first response (CR1, VGPR1, PR1) compared to transplantation in subsequent complete or partial responses or with refractory disease (39% vs 53%; p=0.001), translating into a significant DFS (50% vs 40%, p= 0.004) and OS benefit (71% vs 63%; p= 0.033) for the patients transplanted early. DFS was significantly better for patients receiving ASCT after year 2000 compared to the patients transplanted before (p=0.031) and although the year of ASCT had influence on the OS this did not reach statistical significance (p=0.068). Multivariate analysis considering age, sex, disease status at ASCT, and ASCT year confirmed ASCT beyond 1^st remission (HR 1.37, 95%CI 1.04-1.79), along with female gender (HR 0.73, 95%CI 0.54-0.97) and ASCT between 2001-2005 (vs before 2001; HR 0.66, 95%CI 0.47-0.92) as significant predictors of DFS.

Conclusions: These results suggest that ASCT is a feasible and effective treatment for WM/LPL. Factors predicting for a favourable DFS are female gender, transplantation in the rituximab era, and ASCT in first remission. However, with DFS and OS of 40% and 63% at 5 years, even the outcome of patients undergoing ASCT with advanced disease is still encouraging. As single-hit ASCT can induce long term response with relatively low toxicity and economic burden, it may serve as benchmark for the upcoming novel targeted therapeutics entering the WM / LPL treatment arena.