Prognostic Value of Circulating Bcl-2/Igh Levels before and after Treatment in 415 Patients with Advanced Follicular Lymphoma Receiving First-Line Immuno-Chemotherapy in 2 Prospective StiL Trials - the Effect of Rituximab Maintenance

Introduction. The prognosis of patients with follicular lymphoma (FL) has improved during recent years following the introduction of immuno-chemotherapy and Rituximab maintenance. Nevertheless, some patients still relapse early and have a poor prognosis. Several prognostic scoring systems have been developed using clinical, laboratory as well as molecular data, while the early identification of high-risk patients remains a challenge. In this context, the relevance of circulating bcl2/IgH levels for patient stratification is not clear. We could show that high circulating bcl2/IgH levels in the peripheral blood (PB) before therapy were an independent adverse prognostic factor for progression free survival (PFS) in patients receiving R-CHOP or Bendamustine-Rituximab (B-R) in the NHL1 study of the German StiL group (Zohren et al, Blood 2015).

Methods. Using a sensitive quantitative PCR method as previously described (Zohren et al, Blood 2015), a total of 2,491 circulating bcl-2/IgH level analyses were performed on PB samples before (n=415) and after (n=305) 6 cycles first-line immuno-chemotherapy and during follow-up (n=1,771). Results of these molecular studies were correlated with clinical outcome. We first present a 10-year update of the 107 bcl2/IgH^positive patients from the StiL-NHL1-trial. Secondly, we report the results from the StiL-NHL7-trial including bcl2/IgH analyses of 308 bcl2/IgH^positive patients who received B-R and Rituximab maintenance.

Results. With a median follow-up of 10 years in the 107 bcl2/IgH^positive patients from the StiL-NHL1-trial, high PB bcl-2/IgH levels (bcl-2/IgH to reference gene (tPA) ratio >1) before treatment as compared to low (ratio <1) levels remained a major independent prognostic factor for PFS (median 22 vs 71 months, HR 2.27, 95% CI 1.37-3.75; p=0.001). We also confirm that patients who were still bcl-2/IgH^positive after six cycles of immuno-chemotherapy had significantly inferior PFS (13 vs 79 months, Hazard Ratio (HR) 2.97, 95% CI 1.53-5.78; p=0.001) and overall survival (OS, 128 months vs not reached , HR 3.90, 95% CI 1.39-11.00; p=0.010).

In contrast, among the 308 bcl-2/IgH^positive patients of the StiL-NHL7-trial, who all received B-R and Rituximab maintenance, PB bcl-2/IgH levels (ratio >1 vs <1) before therapy were no longer prognostic for PFS (99 months vs not reached, HR 1.06, 95% CI 0.66 - 1.69; p=0.814) or OS. On the other hand, being bcl-2/IgH^positive after 6x B-R remained a poor prognostic factor for PFS (43 months vs not reached, HR 2.44, 95% CI 1.18-5.04; p=0.016 ) and OS (72 months vs not reached, HR 4.03, 95% CI 1.82-8.96; p=0.001) despite Rituximab maintenance.

When comparing StiL-NHL1 and StiL-NHL7 patients with respect to bcl-2/IgH levels and the effect of Rituximab maintenance, we found that Rituximab maintenance led to a significantly better PFS. In patients with low (ratio <1) bcl-2/IgH levels before therapy the hazard ratio of 1.7 was modest (71 months vs not reached, HR 1.70, 95% CI 1.16-2.50; p=0.006) in comparison to 3.46 as observed in patients with high (ratio >1) bcl-2/IgH levels (22 vs 99 months, HR 3.46, 95% CI 1.93-6.20; p<0.000). These findings suggest that patients with high bcl-2/IgH levels before therapy have a greater benefit from Rituximab maintenance therapy. There was no difference with regard to OS between StiL-NHL1 and StiL-NHL7 patients who were still bcl-2/IgH^positive after 6 cycles of immuno-chemotherapy implying that these patients may not benefit from Rituximab maintenance.

Conclusion. High circulating bcl-2/IgH levels in the PB before first line therapy identify a subgroup of patients with advanced FL who have significantly shorter PFS after standard immuno-chemotherapy. These patients greatly benefit from the addition of Rituximab maintenance, because pre-treatment bcl-2/IgH levels lose their predictive value with Rituximab maintenance therapy. On the other hand, patients who remain bcl-2/IgH^positive after standard immuno-chemotherapy have short PFS and OS despite treatment with Rituximab maintenance and therefore are candidates for experimental treatment approaches.