High prognostic value of measurable residual disease detection by flow cytometry in chronic lymphocytic leukemia patients treated with front-line fludarabine, cyclophosphamide, and rituximab, followed by three years of rituximab maintenance.

It has been postulated that monitoring measurable residual disease (MRD) could be used as a surrogate marker of progression-free survival (PFS) in chronic lymphocytic leukemia (CLL) patients after treatment with immunochemotherapy regimens. In this study, we analyzed the outcome of 84 patients at 3 years of follow-up after first-line treatment with fludarabine, cyclophosphamide and rituximab (FCR) induction followed by 36 months of rituximab maintenance thearpy. MRD was assessed by a quantitative four-color flow cytometry panel with a sensitivity level of 10-4 Eighty out of 84 evaluable patients (95.2%) achieved at least a partial response or better at the end of induction. After clinical evaluation, 74 patients went into rituximab maintenance and the primary endpoint was assessed in the final analysis at 3 years of follow-up. Bone marrow (BM) MRD analysis was performed after the last planned induction course and every 6 months in cases with detectable residual disease during the 36 months of maintenance therapy. Thirty-seven patients (44%) did not have detectable residual disease in the BM prior to maintenance therapy. Interestingly, 29 patients with detectable residual disease in the BM after induction no longer had detectable disease in the BM following maintenance therapy. After a median followup of 6.30 years, the median overall survival (OS) and PFS had not been reached in patients with either undetectable or detectable residual disease in the BM, who had achieved a complete response at the time of starting maintenance therapy. Interestingly, univariate analysis showed that after rituximab maintenance OS was not affected by IGHV status (mutated vs unmutated OS: 85.7% alive at 7.2 years vs 79.6% alive at 7.3 years, respectively). As per protocol, 15 patients (17.8%), who achieved a complete response and undetectable peripheral blood and BM residual disease after four courses of induction, were allowed to stop fludarabine and cyclophosphamide and complete two additional courses of rituximab and continue with maintenance therapy for 18 cycles. Surprisingly, the outcome in this population was similar to that observed in patients who received the full six cycles of the induction regimen. These data show that, compared to historic controls, patients treated with FCR followed by rituximab maintenance have high-quality responses with fewer relapses and improved OS. The tolerability of this regime is favorable. Furthermore, attaining an early undetectable residual disease status could shorten the duration of chemoimmunotherapy, reducing toxicities and preventing long-term side effects. The analysis of BM MRD after fludarabine-based induction could be a powerful predictor of post-maintenance outcomes in patients with CLL undergoing rituximab maintenance and could be a valuable tool to identify patients at high risk of relapse, influencing further treatment strategies. This trial is registered with EudraCT n. 2007-002733-36 and ClinicalTrials.gov Identifier: NCT00545714.

Obinutuzumab plus bendamustine for relapsed/refractory chronic lymphocytic leukemia and predictive and prognostic impact of genetic alterations: the phase II GABRIELL study.

GABRIELL was a phase II single-arm study to evaluate the efficacy and safety of obinutuzumab plus bendamustine for relapsed/refractory (R/R) chronic lymphocytic leukemia (CLL). Seventy-two patients with active disease received treatment for up to six 28-day cycles. Overall response rate was 78.6% with a median progression-free survival (PFS) of 26 months, and overall survival (OS) not reached at the end of follow-up (36 months). Undetectable measurable residual disease (≤0.01%; 36.4% in bone marrow and 53.4% in peripheral blood) correlated with a significantly longer PFS and OS (vs. >0.01). Common grade ≥3 adverse events (76.4%) were neutropenia (58.3%), thrombocytopenia (26.4%) and febrile neutropenia (11.1%). TP53 disruption was the only independent predictive factor for response (Hazard ratio; HR: 0.228). Unmutated immunoglobulin heavy chain variable region (HR: 16.061) was a negative prognostic factor for PFS. In conclusion, the combination of obinutuzumab plus bendamustine is an active and generally adequately-tolerated treatment for R/R CLL.