Prolonged Remission Duration with Interferon Maintenance After Rituximab-Containing Induction in First-Line Advanced Stage Lymphoplasmacytic Lymphoma – a Retrospective Analysis of the German Low-Grade Lymphoma Study Group (GLSG)

Maintenance using interferon-α (IFN) had previously been shown to be effective in indolent lymphoma (Solal-Celigny et al., NEJM 1993, Hagenbeek et al., JCO 1998). However, data on the impact of IFN in lymphoplasmacytic lymphoma (LPL) and after immuno-chemotherapy are rare. In two GLSG first-line trials which included LPL patients, IFN-maintenance was intended in all patients responding to induction therapy and not assigned to high-dose therapy. We performed a retrospective analysis to compare the clinical outcome in LPL patients who received IFN-maintenance versus no consolidation or maintenance. We adjusted for potential confounders that might have influenced the decision not to start IFN-maintenance.

In the GLSG first-line trials “CHOP vs. MCP” and “CHOP vs. R-CHOP” patients younger than 60 years had been randomized between consolidating high-dose radio-chemotherapy followed by autologous stem cell transplantation (ASCT) and IFN-maintenance. IFN-maintenance was also intended in all responding patients older than 60 years. Patients with LPL achieving a partial or complete remission after MCP, CHOP, or R-CHOP and who did not start ASCT were included in the current analysis. We compared patients in which IFN-maintenance was not started to patients with IFN-maintenance. We investigated patient and treatment characteristics of these groups in order to detect possible reasons why IFN-maintenance was not started. Outcome parameters were remission duration (RD) and overall survival (OS). RD, calculated from the end of induction to relapse or death, was censored at the latest follow-up date in patients without event, but also when a new antilymphoma therapy was initiated without any sign of progression. No censoring was done for any form of dose reduction or stopping of IFN, which was recommended in the trials if inacceptable side effects were observed. RD and OS were analysed by Kaplan-Meier curves and log rank test and we adjusted for potential confounders in multiple Cox-Regression. In order to assess the impact of IFN-maintenance after R-containing induction, we performed a subgroup analysis of R-CHOP treated patients.

IFN-maintenance was started in 56 (75%) of 75 responding LPL patients not treated with high-dose therapy. Patients with IFN-maintenance were younger (60 vs. 69 years, p=0.001), but other baseline characteristics (ECOG performance status, haemoglobin, LDH, platelets, β₂-microglobulin, IgM) were comparable, as well as the percentage of patients with R-CHOP induction (64% vs. 63%). More patients treated with IFN had achieved a CR (18% vs. 0%). Patients with IFN-maintenance had significantly longer RD (hazard ratio, HR, 0.27, 95% CI 0.12 to 0.59, p=0.001) and OS (HR 0.19, 95% CI, 0.06 to 0.58, p=0.004) which was similarly seen after adjustment for age (RD: 0.32, 95% CI 0.14 to 0.78, p=0.012, OS: 0.30, 95% CI 0.08 to 1.04, p=0.058), or the achievement of a CR. Of 48 patients responding to R-CHOP, IFN-maintenance was started in 36 (75%). RD after 3 years was 87% vs. 41% (p<0.001) and the HR for IFN adjusted for age were 0.19 for RD (95% CI 0.06 to 0.66 p=0.009) and 0.21 for OS (95% CI 0.04 to 1.05, p=0.058).

Although this is a non-randomized comparison based on a relatively small patient number, our results suggest that IFN-maintenance is effective in LPL also in the era of immuno-chemotherapy. It seems relevant to keep in mind that interferon-a may be a therapeutic option when other strategies are not possible. It may also be relevant for future investigations in lymphoma therapy.

Hoster:Roche: Honoraria. Off Label Use: Interferon-alpha in lymphoplasmacytic lymphoma. Pfreundschuh:Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding. Dreyling:Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Hiddemann:Roche: Research Funding.