Minimal Residual Disease Response Research Articles

Poor Prognosis in Children with ABL-Class Fusion Positive B-Cell Acute Lymphoblastic Leukemia Treated According to AIEOP-BFM Protocols

ABL-class fusions other than BCR-ABL1 (or Ph+) are found in 2-3% of precursor B-cell acute lymphoblastic leukemia (pB-ALL) in children and adolescents. Occasional reports suggest that this rare ALL subtype has a poor prognosis and patients can benefit from treatment with tyrosine kinase inhibitors (TKIs). Aim of this retrospective study is to investigate the presenting features, treatment response and outcome in ABL-class fusion positive cases identified within large cohorts of patients treated in AIEOP-BFM ALL trials. This retrospective survey of ABL-class fusion positive pB-ALL other than Ph+ ALL was performed in patients aged 1-17 years at the diagnosis, treated from October 2000 to August 2018 according to the AIEOP-BFM (Associazione-Italiana- di- Ematologia-Oncologia Pediatrica-Berlin-Frankfurt-Münster) ALL 2000 and 2009 protocols in Austria, Australia, Czech Republic, Germany, Israel, Italy and Switzerland. While ABL-class fusions screening was not required by protocols, it was performed in some patients, according to centers' policies, usually after poor early treatment response. Overall, 46 ABL-class fusion positive cases with ABL1 fusions (N=15), ABL2 fusions (N=5), CSF1R fusions (N=3) and PDGFRB rearrangements (N=23) were identified. Compared with other pB-ALL children and adolescents, the ABL-class fusion positive cases presented with higher proportions of patients aged 10 years or older (52.2 vs. 22.2, P< .0001), hyperleukocytosis (WBC ≥100x109/l, 41.3 vs. 6.3, P< .0001), or poor minimal residual disease (MRD) response (>5x10-4 levels were observed in 65.2% vs. 18%, P< .0001 of patients after induction treatment phase IA and in 45.7% vs. 4.8%, P< .0001 after consolidation phase IB). For the entire cohort of 46 cases, the 5-year probability of event-free survival (EFS) was 49.1+8.9% and that of overall survival (OS) 69.6+7.8%; the cumulative incidence of relapse (CI) was 25.6+8.2% and treatment-related mortality 20.8+6.8%. Although not prescribed by the protocols, 13 patients received a TKI during different phases of treatment (TKI group), by choice of treating physicians, generally due to poor early treatment response. Eight TKI patients with high MRD levels at the end of induction phase IA received the TKI during consolidation phase IB, and six of them achieved either a low positive or negative MRD level at the end of consolidation phase IB. Nine of the 13 patients treated with TKIs underwent hematopoietic stem cell transplantation (HSCT) and only 1/9 (TKI+HSCT) relapsed. Thirty-three cases did not receive any TKI (no-TKI group) and eight of them relapsed; 6/17 patients treated with chemotherapy only, versus only 2/16 who underwent HSCT. Overall, 25 patients underwent HSCT, and of them 3 relapsed and 6 died of treatment-related complications. In patients with a WBC higher or lower than 100x109/L, the 5-year EFS was 36.8+12.7% vs. 59.9+11.6%, respectively (P= .21), and the 5-year OS was significantly lower in patients with a high WBC (48.8+12.9% vs. 87.4+6.8%, P= .036). This difference was more pronounced in the no-TKI group with a 5-year EFS 27.8+13.6% vs 61.8+12.7%, (P= .07), and an OS of 36.7+14.6% vs 94.4+5.4%, respectively (P= .0015). Presenting features, treatment response and outcome in this cohort of ABL-class fusion positive patients are markedly similar to those of patients with Ph+ ALL included in the EsPhALL studies. Our results suggest that TKIs and HSCT may be beneficial in reducing the risk of relapse. Thus there is an urgent need for large international cooperative controlled studies to investigate the impact of TKI, in combination with an appropriate chemotherapy backbone and the role of HSCT. To this purpose, an early identification of patients with ABL-class fusion positive acute lymphoblastic leukemia will be necessary. Disclosures Izraeli: sightdx: Consultancy; novartis: Honoraria; prime oncology: Speakers Bureau. Locatelli:Miltenyi: Honoraria; bluebird bio: Consultancy; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bellicum: Consultancy, Membership on an entity's Board of Directors or advisory committees. White:BMS: Honoraria, Research Funding; AMGEN: Honoraria, Speakers Bureau. Schrappe:Together with study group from SHIRE, JazzPharma, Servier, SigmaTau, Amgen, and Novartis.: Research Funding; SHIRE, Servier, and JazzPharma: Honoraria.

Intensive Chemotherapy for High-Risk ALL in Children - the Nordic Collaborative Approach

OS for childhood ALL is now >90%, but high-risk (HR) cases still need to improve. The NOPHO ALL2008 protocol restricted very intensive HR chemotherapy to patients with an inferior early minimal residual disease (MRD) response or HR genetics, and we here report the results for this subset. HR patients had WBC >100K at diagnosis and/or T-ALL; and an MRD of either >25% day 15 or >0.1% day 29; and/or a KMT2A-re or hypodiploidy (<45 chr). MRD was assessed by flow cytometry (BCP) or PCR (T-ALL). If no marker was found with one, the alternative method was used. Thus, >98% had a suitable MRD marker. All HR patients received a 3-drug induction chemotherapy (VCR 2 mg/m2 x5), DOX (40 mg/m2 x2), PRED (60 mg/m2/d for 4 weeks for BCP-ALL with WBC <100K) or DEXA (10 mg/m2/d for 3 weeks for all others). This was followed by 9 (A1-B1-C1-A2-B2-C2-A3-B3-C3) or 7 (if MRD after 1st HR block <0.1%; C2/C3 deleted) blocks, 60 weeks of interim maintenance with oral 6MP/MTX and HD-MTX x3 (5g/m2/d), delayed intensification, and maintenance therapy until a total of 2.5 years from diagnosis. Post-induction, a total of 12 doses of i.m. Peg-asp (1,000 IU/m2) was given (Toft, Leukemia 2018). A-blocks included cyclophosphamide (440 mg/m2/d x5), etoposide (100 mg/m2/d x5), and Peg-asp (1000 IU/m2). B-blocks consisted of HD-MTX (5g/m2), HD-AraC (2x2g/m2 /d x2), 6MP (100 mg/m2/d x5), DEXA (20 mg/m2/d x5), VCR (2 mg/m2 x2), Peg-asp (1000 IU/m2). C-blocks included idarubicin (8 mg/m2), fludarabine (30 mg/m2/d x5), HD-AraC (2g/m2 /d x5), Peg-asp (1000 IU/m2). Patients were allocated to hSCT if MRD >5% at end of induction, or >0.1% after 2 HR-blocks or ~3 months of LR-chemotherapy. HSCT-patients are not included here. Data on 18 toxic adverse events was prospectively collected at three-month intervals. The Kaplan-Meier method was used for OS and EFS analyses. CI of Rel (CIR) and TRM (CITRM) were estimated accounting for competing events. Cox-models were used to compute hazard ratios and proportional hazard assumptions were evaluated using Schoenfeld residuals. 132 subjects 1-≤18 years of age at diagnosis were eligible for HR chemotherapy accounting for 16% of the study cohort with a median age of 6.6 years as compared to 4.6 years in the entire cohort. Of the HR chemotherapy subjects 26% received PRED in induction. Five-year EFS was 67% (95% CI, 59-76%) and OS was 74% (95% CI, 67-82%) in the HR chemo cohort. CIR at five years was 18% (95% CI, 11-24%). We found no difference in EFS by cell lineage (BCP-ALL: 69%, 95% CI, 59-80% vs. T-ALL 65%, 95% CI 52-77%). KMT2A-re occurred in 34 patients, 62% of whom had MRD <0.1% after induction. Their five-year EFS and OS were 88% (95% CI, 77-99%). KMT2A-re patients with a leukocyte count <100K and EOI MRD <0.1% had no relapses, but toxic deaths resulting in a 5-year EFS of 80% (95% CI, 55-100%). Hypodiploid patients had a five-year EFS and OS of 55% (95% CI, 34%-76%) and 58% (95% CI, 39-78%), respectively. Strikingly, KMT2A-re and hypodiploid patients with a negative MRD at EOI, suffered no relapses. 29 patients shifted to HR-blocks at day 15 due to MRD >25% (T-ALL (N=17), BCP with WBC >100K (N=7), KMT2A-re (N=4), or hypodiploid ALL (N=1). Their five-year EFS was 47% (95% CI, 21-73%) and CIR 44% (95% CI, 18-70%). During the HR chemotherapy blocks, 70% (N=93) of patients encountered at least one toxic event beyond bacteremia and febrile neutropenia, the most common of which was fungal infections (25%), referral to intensive care (23%), and asparaginase associated anaphylaxis (21%). The NOPHO ALL2008 stratification strategy led to allocation of 16% of patients to the HR arm with an EFS of 67% and OS of 74%. Due to the intensity of chemotherapy a significant risk of toxic death was encountered, and the risks of toxic death and relapse were very similar. Patients with rearranged KMT2A and a low EOI MRD could be candidates for future reduction of treatment intensity. These findings are integrated into the upcoming European ALLTogether1 protocol opening in 14 European countries early 2020, where the use of the NOPHO ALL2008 HR blocks will be restricted to the 3% of patients with the poorest prognosis. Figure - EFS with 95% Cis, CITRM (short dash) and CIR (long dash) for the NOPHO ALL-2008 high-risk chemotherapy patients Disclosures No relevant conflicts of interest to declare.

High Sensitivity NGS Analysis of MRD in CLL Patients Prospectively Treated with Ibrutinib Plus FCR (iFCR)

High Sensitivity NGS Analysis of MRD in CLL Patients Prospectively Treated with Ibrutinib Plus FCR (iFCR)

Quantitative Analysis of Minimal Residual Disease (MRD) Shows High Rates of Undetectable MRD after Fixed-Duration Chemotherapy-Free Treatment and Serves As Surrogate Marker for Progression-Free Survival: A Prospective Analysis of the Randomized CLL14 Trial

Fischer: Roche: Other: travel grants; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees. Ritgen:AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel support, Research Funding. Al-Sawaf:Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel support; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel support; Janssen: Membership on an entity's Board of Directors or advisory committees, Other: travel support; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel support. Tandon:Roche: Equity Ownership; Roche Products Ltd: Employment. Fink:Janssen: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; Roche: Other: travel grants. Stübig:Hexal: Speakers Bureau. Brüggemann:Amgen, Celgene, Janssen: Honoraria, Speakers Bureau; Amgen, Janssen: Membership on an entity's Board of Directors or advisory committees; affimed, Amgen, Celgene, Regeneron: Research Funding; Amgen, Incyte, PRMA: Consultancy. Jiang:Genentech: Employment, Equity Ownership; F. Hoffman-La Roche: Equity Ownership. Schary:Abbvie: Employment, Equity Ownership. Eichhorst:Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; BeiGene: Research Funding; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead Sciences, Inc.: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; ArQule: Membership on an entity's Board of Directors or advisory committees. Wendtner:MorphoSys: Consultancy, Honoraria, Research Funding; GILEAD Science: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria, Research Funding; Janssen-CILAG: Consultancy, Honoraria, Research Funding; Novartis: Honoraria, Research Funding; F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Research Funding; Mundipharma: Honoraria, Research Funding. Tausch:AbbVie: Consultancy, Honoraria, Other: travel support, Speakers Bureau; Roche: Consultancy, Honoraria, Speakers Bureau. Kreuzer:Roche and Abbvie: Honoraria, Other: Expert testimony. Langerak:F. Hoffmann-La Roche Ltd: Research Funding; Gilead: Research Funding, Speakers Bureau; Janssen: Speakers Bureau; Genentech, Inc.: Research Funding. Goede:Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel grants, speaker fees, Speakers Bureau; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: speaker fees, Speakers Bureau; janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel grants, speaker fees, Speakers Bureau. Böttcher:AbbVie: Honoraria, Other: Travel grants, Research Funding; Celgene: Research Funding; Janssen-CILAG: Honoraria, Other: Travel grants, Research Funding; Roche: Honoraria, Research Funding; Genentech: Research Funding; Becton Dickinson: Research Funding; Novartis: Research Funding. Stilgenbauer:AstraZeneca: Consultancy, Honoraria, Research Funding, Speakers Bureau; AbbVie: Consultancy, Honoraria, Research Funding, Speakers Bureau; Amgen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Pharmacyclics: Other: Travel support; Gilead: Consultancy, Honoraria, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Novartis: Consultancy, Honoraria, Research Funding, Speakers Bureau; GSK: Consultancy, Honoraria, Research Funding, Speakers Bureau; Celgene: Consultancy, Honoraria, Research Funding, Speakers Bureau; Hoffmann La-Roche: Consultancy, Honoraria, Research Funding, Speakers Bureau. Hallek:Roche, Gilead Sciences, Inc., Mundipharma, Janssen, Celgene, Pharmacyclics, AbbVie: Honoraria, Research Funding, Speakers Bureau.

Prognostic Value of Minimal Residual Disease Measured By Flow Cytometry in Two Cohorts of Infants with Acute Lymphoblastic Leukemia Treated with MLL-Baby and Interfant Protocols in Large Multicenter Networks

Acute lymphoblastic leukemia (ALL) in infants is a relatively rare disease with peculiar biological features, high frequency of KMT2A gene rearrangements and grim prognosis. Even with new therapeutic approaches, event-free survival (EFS) in infants with ALL does not exceed 50%. Currently large cooperative studies of infant ALL have been promoted by the Interfant and MLL-Baby networks. Minimal residual disease (MRD) monitoring is considered a strong tool for optimizing management of childhood ALL. In contrast to older children in this age group the prognostic impact of MRD detected by multicolor flow cytometry (MFC) is still unclear. Aim of the present study was to evaluate the prognostic value of MFC MRD measurement during induction in infants with ALL treated with Interfant-99 and Interfant-06 protocols in AIEOP centers in Italy as well as MLL-Baby protocol in Russia and Belarus. Patients and methods. Two independent groups of patients were investigated: study cohort of 139 consecutive infants with newly diagnosed ALL enrolled between September 2003 and April 2016 in Russian and Belorussian centers with MLL-Baby protocol and validation group of 146 ones enrolled in AIEOP centers in Interfant trials during the same period. By availability of MFC MRD data obtained at day 15 and/or end of induction (EOI), 81 and 86 patients of study and validation cohorts respectively were selected for outcome evaluation. In 61 MLL-Baby patients (75.3%) and 61 AIEOP cases (70.9%) different types of KMT2A gene rearrangements were identified. All patients were diagnosed as BCP-ALL, except one with cortical T-ALL. Overall, day 15 samples were studied in 64 MLL-Baby patients and 73 AIEOP cases while EOI samples in 75 and 63 cases respectively. MRD detection was performed in Reference Laboratories in Ekaterinburg, Minsk and Padua according the BFM AIEOP FLOW Network SOP. MRD negativity was defined as <0.01% of all bone marrow nucleated cells. Results. Patients were stratified according to the AIEOP-BFM-ALL day 15 stratification usually used for older children into three risk groups: standard risk (SR: MRD<0.1%), intermediate risk (IR: MRD 0.1% to 10%) and high risk (HR: MRD≥10%). Patients' distribution was similar in both study and validation cohorts: 34.4% and 32.9% in SR, 53.1% and 54.5% in ImR, 12.5% and 12.3% in HR respectively. At EOI significant differences in MRD-positive and MRD-negative patients' distribution was observed in different protocols: 44 (58.7%) and 31 (41.3%) cases respectively for MLL-Baby, but 17 (27.0%) and 46 (73.0%) cases respectively for AIEOP group. It was observed that KMT2A-rearranged cases in both trials have slower MRD response compared to the children with wild type KMT2A. In study cohort the 22 SR patients had a 5-year EFS and cumulative incidence of relapse (CIR) significantly better than other ones, thus we considered two major groups of patients with different outcome: SR with 5-year EFS 67.4%, standard error (SE) 10.2; CIR 23.3%, SE 9.4 and non-SR with 5-year EFS 30.8%, SE 7.2; CIR 52.6%, SE 7.9, (p=0.0039 and p=0.0229, respectively). Difference between these groups was observed also in KMT2A-rearranged cases (n=49) both for 5-year EFS (60.0%, SE 12.7 and 23.2%, SE 7.3, p=0.0160) and in 5-year CIR (33.3%, SE 12.7 and 59.2%, SE 8.8, p=0.0881). Analysis of outcome in validation cohort confirmed these data. In study cohort outcome of children being MRD-negative at EOI (n=31, 5-year EFS 60.8%, SE 8.8 and CIR 29.3%, SE 8.4) was significantly better than that of MRD-positive patients (n=44, 5-year EFS 31.1%, SE 7.1 and CIR 57.6%, SE 7.8 with p=0.0153 and p=0.0267, respectively). Outcome by EOI MFC MRD in the validation cohort is generally in keeping with that of the study cohort. Interestingly, in AIEOP cohort MFC data showed a prognostic impact also in KMT2A-rearranged subgroup. In multivariate analysis with KMT2A-status, each MRD time-point data showed independent impact on the risk of relapse. Conclusion. Our data was obtained by well-harmonized MFC MRD monitoring in a large group of infants with ALL treated in a multicenter setting with two different protocols. In spite of differences in therapy, we observed strong and independent prognostic impact of MFC MRD both at day 15 and at EOI regardless the protocol applied. We can conclude that MFC MRD can be used in combination with KMT2A-status to improve treatment allocation in future protocols. Disclosures Parasole: Servier: Honoraria; Baxalta: Honoraria; Eusapharma: Honoraria. Pieters:jazz farmaceuticals: Consultancy; medac: Consultancy.

Preliminary Minimal Residual Disease Analysis of the Australasian Leukaemia & Lymphoma Group (ALLG) ALL8 Study of Front-Line Blinatumomab with Chemotherapy in Adults with Ph Negative B-Cell Acute Lymphoblastic Leukaemia

Preliminary Minimal Residual Disease Analysis of the Australasian Leukaemia & Lymphoma Group (ALLG) ALL8 Study of Front-Line Blinatumomab with Chemotherapy in Adults with Ph Negative B-Cell Acute Lymphoblastic Leukaemia

High Interpatient Variability in Molecular MRD Response to Consolidation Chemotherapy in Acute Myeloid Leukemia

High Interpatient Variability in Molecular MRD Response to Consolidation Chemotherapy in Acute Myeloid Leukemia

Post-Remission Treatment with Chemotherapy or Allogeneic Hematopoietic Stem Cell Transplantation (alloHSCT) in Adult Patients with High-Risk (HR) Philadelphia Chromosome-Negative (Ph-neg) Acute Lymphoblastic Leukemia (ALL) According to Their Minimal Residual Disease (MRD). Final Results of the Pethema ALL-HR-11 Trial

Introduction: Recent studies have shown that young to middle-aged adults who receive a pediatric-inspired chemotherapy regimen for treatment of Ph-neg ALL do not appear to require an alloHSCT if they achieve good response on MRD testing after induction and/or consolidation therapy. Patients (pts) who are not good MRD responders achieve better outcomes with alloHSCT than their counterparts who do not receive alloHSCT. However, it is not clear if this approach can specifically apply to adult ALL pts with HR features at baseline. The aim of the prospective ALL-HR-11 trial (NCT01540812) from the Spanish PETHEMA Group was to evaluate response of HR Ph-neg adult ALL patients to a different post-induction therapy (chemotherapy or alloHSCT) according to MRD levels (centrally assessed by 8-color flow cytometry [FCM]) at the end of induction (week 5) and consolidation therapy (week 17).. Patients and methods: HR ALL included one or more of the following parameters at baseline: age 30-60y, WBC count >30x109/L for B-cell precursor ALL or >100x109/L for thymic T-ALL, pro-B, early or mature T-ALL, 11q23 or KMT2A rearrangements or complex karyotype. Induction therapy included vincristine, prednisone, daunorubicin and asparaginase (E coli native or PEG according to center availability) for 4 weeks (Induction-1). FLAG-Ida was administered as intensified induction (Induction-2) in pts not achieving CR or in those in CR with MRD≥0.1% at the end of induction. For pts in CR and MRD<0.1% early consolidation therapy included 3 cycles with rotating cytotoxic drugs with high-dose methotrexate, high-dose ARA-C and high-dose asparaginase (E coli native or PEG). These pts continued with delayed consolidation (identical to that of early consolidation) followed by maintenance therapy up to 2y in CR if MRD levels after consolidation were <0.01%; otherwise they were assigned to alloHSCT. Pts in CR after Induction-2 received one consolidation cycle and were assigned to alloHSCT. Main outcome measures were: complete response (CR), overall survival (OS) and cumulative incidence of relapse (CIR), assessed by competing risk analysis. Results: On April 2019, 307 HR ALL pts were evaluable. Median (range) age was 40 (15-60) y, 192 were males, 211 precursor B-ALL and 96 T-ALL, with a median WBC count of 12.9 (0.2-564) x109/L. Results of Induction-1 (n=304, 3 on induction): therapy-related death: 12(4%), resistance: 39(13%), CR: 253(83%). MRD<0.1% at the end of induction was observed in 77% of CR patients. Induction-2 was administered to 88 patients (due to no CR: 37, or to CR and MRD≥0.1%: 51). Overall response rate: 277 (91%). The 5y CIR and OS probabilities for the whole series were of 44%±8% and 48%±7% (median follow-up: 2.06y [range: 0-7.55y]). By intention-to treat after Induction-1, 94 pts were assigned to alloHSCT and 190 to delayed consolidation and maintenance. The 5y CIR and OS probabilities were of 37%±13% and 38%±11%, respectively, for pts assigned to alloHSCT, and of 48%±10% and 55%±10%, respectively, for those assigned to chemotherapy (P<0.001 for OS [Figure 1], and P=0.243 for CIR). Patients with MRD<0.1% at the end of induction and MRD<0.01% at the end of consolidation (n=137) showed a 5y CIR and OS of 42%±11% and 66%±11%, respectively (P<0.001 for both, Figure 2). Patients with MRD levels <0.01% on day14 of induction-1, end-induction-1 and end-consolidation (n=17) showed 5y CIR and OS probabilities of 17%±19% and 90%±19%, respectively. Conclusions: This trial, in which post-induction therapy was only based on MRD results assessed by FCM, suggests that avoiding alloHSCT does not hamper the outcome of HR Ph-neg adult ALL pts with adequate MRD response after induction and after consolidation. Better post-remission alternative therapies are specially needed for patients with poor MRD clearance. Supported by grants PI14/01971 FIS, Instituto Carlos III, and SGR225 (GRE), Spain. Disclosures Montesinos: Novartis: Membership on an entity's Board of Directors or advisory committees, Other: Research support, Research Funding, Speakers Bureau; Teva: Membership on an entity's Board of Directors or advisory committees, Other: Research support, Research Funding, Speakers Bureau; Incyte: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Research support, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Other: Research support, Research Funding, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Research support, Speakers Bureau; Karyopharm: Membership on an entity's Board of Directors or advisory committees, Other: Research support; Pfizer: Membership on an entity's Board of Directors or advisory committees, Other: Research support, Research Funding, Speakers Bureau. Esteve:Novartis: Consultancy, Research Funding, Speakers Bureau; Roche: Consultancy; Pfizer: Consultancy; Astellas: Consultancy, Speakers Bureau; Amgen: Consultancy; Celgene: Consultancy, Speakers Bureau; Daiichi Sankyo: Consultancy; Jazz Pharmaceuticals: Consultancy.

Sequential Combination of Inotuzumab Ozogamicin (InO) with Low-Intensity Chemotherapy (Mini-hyper-CVD) with or without Blinatumomab Is Highly Effective in Patients (pts) with Philadelphia Chromosome-Negative Acute Lymphoblastic Leukemia (ALL) in First Relapse

Sequential Combination of Inotuzumab Ozogamicin (InO) with Low-Intensity Chemotherapy (Mini-hyper-CVD) with or without Blinatumomab Is Highly Effective in Patients (pts) with Philadelphia Chromosome-Negative Acute Lymphoblastic Leukemia (ALL) in First Relapse

T-cell acute lymphoblastic leukemia in patients 1-45 years treated with the pediatric NOPHO ALL2008 protocol.

The NOPHO ALL2008 is a population-based study using an unmodified pediatric protocol in patients 1-45 years of age with acute lymphoblastic leukemia. Patients with T-ALL were given a traditional pediatric scheme if fast responding (minimal residual disease (MRD) < 0.1% day 29), or intensive block-based chemotherapy if slow responding (MRD > 0.1% day 29). Both treatment arms included pediatric doses of high-dose methotrexate and asparaginase. If MRD ≥ 5% on day 29 or ≥0.1% after consolidation, patients were assigned to allogeneic hematopoietic stem cell transplantation. The 5-year overall survival of the 278 T-ALL patients was 0.75 (95% CI 0.69-0.81), being 0.82 (0.74-0.88) for patients 1.0-9.9 years, 0.76 (0.66-0.86) for those 10.0-17.9 years, and 0.65 (0.55-0.75) for the older patients. The risk of death in first remission was significantly higher in adults (12%) compared with the 1-9 years group (4%). The MRD responses in the three age groups were similar, and only a nonsignificant increase in relapse risk was found in adults. In conclusion, an unmodified pediatric protocol in patients 1-45 years is effective in all age groups. The traditional pediatric treatment schedule was safe for all patients, but the intensive block therapy led to a high toxic death rate in adults.

Minimal Residual Disease Status as a Surrogate Endpoint for Progression-free Survival in Newly Diagnosed Multiple Myeloma Studies: A Meta-analysis

BackgroundTherapeutic advances have greatly extended survival times in patients with multiple myeloma, necessitating increasingly lengthy trials when using survival outcomes as primary endpoints. A surrogate endpoint that can more rapidly predict survival could accelerate drug development. We conducted a meta-analysis to evaluate minimal residual disease (MRD) status as a valid progression-free survival (PFS) surrogate in patients with newly diagnosed multiple myeloma (NDMM). Materials and MethodsWe searched abstracts in PubMed, The American Society of Hematology, and the European Hematology Association for “myeloma,” “minimal residual disease,” and “clinical trial.” Because of the need to evaluate the treatment effect on MRD response, only randomized studies for subjects with NDMM were included. Details on the MRD-tested populations were required. The meta-analysis was performed by principles outlined at the 2013 United States Food and Drug Administration workshop on MRD in acute myeloid leukemia.42 For samples that were not measured for MRD and within the subset specified for MRD assessment, their MRD status was imputed from the samples that had known MRD status. Patients that were excluded from planned MRD assessment were considered MRD-positive. ResultsSix randomized studies, representing 3283 patients and 2208 MRD samples, met analysis inclusion criteria. MRD negativity rates ranged from 0.06 to 0.70. The treatment effect on the odds ratio for MRD-negative response strongly correlated with the hazard ratio for PFS with a coefficient of determination for the weighted regression line of 0.97. Our meta-analysis suggested that MRD status met both the Prentice criteria for PFS surrogacy. ConclusionsThese results support the claim that MRD status can be used as a surrogate for PFS in NDMM.

Therapy of nodal Follicular Lymphoma (WHO grade 1/2) in clinical stage I/II using response adapted Involved Site Radiotherapy in combination with Obinutuzumab (Gazyvaro) - GAZAI Trial (GAZyvaro and response adapted Involved-site Radiotherapy): a study protocol for a single-arm, non-randomized, open, national, multi-center phase II trial

BackgroundLarge field irradiation had been standard for early-stage follicular lymphoma (FL) for a long time. Although involved field radiotherapy (IF-RT) was recently favored because of the toxicity of large field irradiation, smaller irradiation fields have been accompanied with an increased risk of out-of-field recurrence. The MIR (MabThera® and Involved field Radiation) trial has shown that the combination of IF-RT at a dose of 30–40 Gy with the anti-CD20 antibody rituximab has led to similar efficacy compared with large field irradiation but with markedly reduced side effects. Immune modulating radiation therapy alone using low-dose radiotherapy (LDRT) of 2 × 2 Gy has been shown to be effective in FL. The GAZAI (GAZyvaro and response Adapted Involved-site Radiotherapy) trial aims to prove the efficacy of LDRT in combination with a novel anti-CD20 therapy.Methods/designThe GAZAI trial is a non-randomized, open, non-controlled, German, multi-center phase II trial that includes patients with early-stage (I and II) nodular FL (grades 1 and 2) confirmed by central histological review. A maximum of 93 patients will be included in the trial. Patients will receive a combined approach of immunotherapy with the fully humanized anti-CD20 antibody obinutuzumab (Gazyvaro®) and involved site radiotherapy (IS-RT) with 2 × 2 Gy. The primary endpoint of the trial is the rate of metabolic complete response (CR), based on fludeoxyglucose positron emission tomography/computed tomography, after obinutuzumab and 2 × 2 Gy IS-RT in week 18. Secondary endpoints are morphologic CR rate in weeks 7 and 18 and month 6, progression-free survival, toxicity, recurrence patterns, overall survival, and quality of life. Additionally, minimal residual disease response is assessed. The risk for a potentially higher recurrence rate after LDRT will be minimized by additional salvage radiation up to the “full dose” of 40 Gy for patients who have less than a metabolic CR and morphologic partial response/CR, which will be evaluated in week 18, offering a response-adapted approach.DiscussionThe goal of this trial is a further reduction of the radiation dose in patients with nodal early-stage FL showing a good response to a combination of LDRT and anti-CD20 immunotherapy and a comparison with the currently published MIR trial.Trial registrationEudraCT number: 2016-002059-89. ClinicalTrials.gov identifier: NCT03341520.

MRD response in relapsed/refractory FL after obinutuzumab plus bendamustine or bendamustine alone in the GADOLIN trial

We report assessment of minimal residual disease (MRD) status and its association with outcome in rituximab-refractory follicular lymphoma (FL) in the randomized GADOLIN trial (NCT01059630). Patients received obinutuzumab (G) plus bendamustine (Benda) induction followed by G maintenance, or Benda induction alone. Patients with a clonal marker (t[14;18] translocation and/or immunoglobulin heavy or light chain rearrangement) detected at study screening were assessed for MRD at mid-induction (MI), end of induction (EOI), and every 6–24 months post-EOI/discontinuation by real-time quantitative PCR. At MI, 41/52 (79%) patients receiving G-Benda were MRD-negative vs. 17/36 (47%) patients receiving Benda alone (p = 0.0029). At EOI, 54/63 (86%) patients receiving G-Benda were MRD-negative vs. 30/55 (55%) receiving Benda alone (p = 0.0002). MRD-negative patients at EOI had improved progression-free survival (HR, 0.33, 95% CI, 0.19–0.56, p < 0.0001) and overall survival (HR, 0.39, 95% CI, 0.19–0.78, p = 0.008) vs. MRD-positive patients, and maintained their MRD-negative status for longer if they received G maintenance than if they did not. These results suggest that the addition of G to Benda-based treatment during induction can significantly contribute to the speed and depth of response, and G maintenance in MRD-negative patients potentially delays lymphoma regrowth.

Transplantation in adults with relapsed/refractory acute lymphoblastic leukemia who are treated with blinatumomab from a phase 3 study.

Blinatumomab, a bispecific T-cell-engaging (BiTE®) immuno-oncology therapy, demonstrated superior overall survival versus standard-of-care chemotherapy (SOC) in adults with relapsed/refractory B-cell precursor acute lymphoblastic leukemia (R/R ALL) in the phase 3 TOWER study. Herein, the authors reported clinical features and outcomes for those patients who underwent allogeneic hematopoietic stem cell transplantation (HSCT) after treatment with blinatumomab. In the TOWER study, adults with R/R ALL were randomized 2:1 to receive blinatumomab or SOC. Study treatment consisted of 2 cycles of induction with blinatumomab or SOC followed by consolidation and maintenance therapy. At any time after the first cycle, patients who were eligible for HSCT could proceed to HSCT. Of the 97 patients who underwent HSCT during the study, baseline characteristics generally were comparable and donor types were similar between the patients treated with blinatumomab (65 patients) and those receiving SOC (32 patients). There was no evidence to suggest that the survival benefit of HSCT differed between the patients treated with blinatumomab and those receiving SOC (P=.68). On the basis of descriptive statistics, a survival benefit of HSCT versus no HSCT was not observed in patients who achieved complete remission with full, partial, or incomplete hematologic recovery with blinatumomab (odds ratio, 1.17; 95% CI, 0.54-2.53). The best outcomes were achieved in patients with no prior salvage therapy and with minimal residual disease response to blinatumomab regardless of on-study HSCT status. Survival was found to be driven by response to study treatment and by salvage status regardless of on-study HSCT status. These data should be interpreted with caution because the current study was not designed to prospectively assess survival outcomes associated with HSCT after blinatumomab. Evidence before this study: Blinatumomab is associated with superior morphologic and molecular response rates and superior overall outcome when compared with standard of care chemotherapy in adults with relapsed/refractory B-cell precursor acute lymphoblastic leukemia. Added value of this study: The best outcomes with blinatumomab were observed in patients who achieved minimal residual disease remission in first salvage treatment regardless of subsequent allogeneic stem cell transplantation (HSCT). Implications of all the available evidence: Patients achieving CR/CRh/CRi following blinatumomab can have a durable response with or without HSCT.

PS948 EXCELLENT RESPONSE TO BLINATUMOMAB IN REFRACTORY B LINEAGE ACUTE LYMPHOBLASTIC LEUKAEMIA IN CHILDREN AND YOUNG ADULTS AFTER DEBULKING CHEMOTHERAPY TO ACHIEVE PARTIAL REMISSION

Background:A recent phase I/II study of blinatumomab in children with relapsed/refractory B cell acute lymphoblastic leukaemia (B‐ALL), found 39–51% achieved complete, often MRD negative, remission after two cycles of therapy. Higher responses were observed in patients with less than 50% bone marrow blasts, compared to greater than 50% (55.6% vs 32.7% (95% CI 30.8–78.5 and 20.3–47.1 respectively). Furthermore, an adult study showed complete minimal residual disease (MRD) response rates of 78% when blinatumomab was used to treat MRD‐positive ALL in haematological remission. Hence response rates (and toxicity) to blinatumomab are highly correlated with pre‐treatment disease burden.Aims:We aimed to determine the outcome of children and young adults who received blinatumomab for primary refractory or relapsed B‐ALL, who had persistent MRD, or after debulking chemotherapy to achieve a partial remission.Methods:Eighteen patients were identified through a national survey. The mean age of patients was 8 years (range 0.5‐ 22), 4 infants and 1 Down syndrome ALL). All patients had B‐lineage ALL which was CD19 positive. None had active CNS disease at the point of receiving blinatumomab. Prior to administration of blinatumomab, all patients either had persistent MRD following several courses of intensive chemotherapy or received debulking chemotherapy for heavier marrow infiltrates. Pre‐blinatumomab chemotherapy to which the patients had failed to obtain an adequate MRD response included UKALL 2011 Regimens A or C, UKALL R3, Interfant 06, FLA‐IDA or NOPHO high risk blocks. Patients received 5–15 μg/m2 of blinatumomab for 1–2 cycles prior to definitive therapy.Results:Pre‐blinatumomab, all patients except two were in morphological remission with MRD measurable by PCR (0.003–6%), the remaining patient had 15 and 32% marrow disease by morphology. After 1–2 cycles of blinatumomab all patients had negative MRD when measured by flow cytometry and/or by PCR, giving a 100% response rate. This was followed by haemopoietic stem cell transplant (HSCT) in 17 patients, and of these, 11 are currently alive and disease‐free. Three patients died from transplant‐related complications, without evidence of disease recurrence. One patient had a lineage switch relapse post‐transplant and 2 with CD19 positive relapse 3–7 months post‐transplant have received CART cells. One patient is awaiting CART cells having relapsed 2 weeks after 1 cycle of blinatumomab.Minimal toxicity was observed; 6 patients had grade 1–2 CRS, which resolved spontaneously without interruption of therapy or treatment with corticosteroids or Tocilizumab. Two patients reported grade neurotoxicity (grade 1+3).Summary/Conclusion:This preliminary UK experience demonstrates that excellent MRD response is observed with minimal toxicity in children and young adults who receive blinatumomab for persistent MRD or after debulking chemotherapy which provides an opportunity for transplant in otherwise ineligible patients.

The poor prognosis of low hypodiploidy in adults with B-cell precursor acute lymphoblastic leukaemia is restricted to older adults and elderly patients.

The prognostic significance of low-hypodiploidy has not been extensively evaluated in minimal residual disease (MRD)-oriented protocols for adult acute lymphoblastic leukaemia (ALL). We analysed the outcome of hypodiploid adult ALL patients treated within Programa Español de Tratamientos en Hematología (PETHEMA) protocols. The 5-year cumulative incidence of relapse (CIR) of low-hypodiploid B-cell precursor (BCP)-ALL was significantly higher than that of high-hypodiploids (52% vs. 12%, P=0.013). Low-hypodiploid BCP-ALL patients aged ≤35years showed superior survival (71% vs. 21%, P=0.026) and lower 5-year CIR (17% vs. 66%, P=0.090) than low-hypodiploids aged >35years. Older adults and elderly low-hypodiploid BCP-ALL patients show dismal prognosis although achieving an end-induction good MRD response.

Rituximab With Involved Field Irradiation for Early-stage Nodal Follicular Lymphoma: Results of the MIR Study.

The MabThera and Involved field Radiotherapy study investigated efficacy and safety of involved field (IF) radiotherapy in combination with the anti-CD20 antibody Rituximab for early-stage follicular lymphoma (FL) in a prospective, single-arm multicenter phase 2 design. Eighty-five stage I–II FL patients received 8 cycles of Rituximab (375 mg/m2) and IF irradiation (30/40 Gy). The primary endpoint was progression-free survival (PFS) 2 years from treatment start. Secondary endpoints were overall survival (OS), complete response rates, toxicity, quality of life, and minimal residual disease (MRD) response with protocol defined visits up to month 30. For the primary endpoint, PFS at 2 years was 85% for the intention-to-treat set. Long-term data were captured in selected sites and evaluated as post hoc analysis in the per protocol (PP) set: PFS and OS were 78% and 96% at 5 years with a median follow-up of 66 or 78 months, respectively. There were 17/76 recurrences in the PP set, of which 14 were outside the radiation volume only. MRD analyses revealed a clonal marker in 36% of patients at diagnosis. All but 1 marker positive patients experienced a molecular treatment response. There were 13 serious adverse events (4 related to the therapy) during the first 30 months. IF radiotherapy combined with Rituximab is well tolerated and highly efficient with low rates of recurrence in the first years in early-stage FL. The efficacy is comparable with more aggressive therapy approaches without compromising the quality of life and maintains for an extended follow-up of more than 5 years.

Antibody-based therapies in patients with acute lymphoblastic leukemia.

The use of multiagent combination chemotherapy regimens results in cure rates of >90% for children and ∼40% for adults with acute lymphoblastic leukemia (ALL) but is associated with extensive toxicity and disappointingly low efficacy in relapsed patients. ALL blast cells express several surface antigens, including CD20, CD22, and CD19, which represent valuable targets for immunotherapy. Monoclonal antibodies, antibody-drug conjugates, and bispecific T-cell-engaging antibodies targeting these antigens offer novel mechanisms of action. Within the last several years, the anti-CD20 antibody rituximab has been added to chemotherapy for newly diagnosed patients <60 years with CD20+ pre-B ALL and significantly improved the 2-year event-free survival from 52% to 65%. In adults with relapsed or refractory CD22+ ALL, the antibody-drug conjugate inotuzumab ozogamicin resulted in a complete response rate of 81% and median overall survival of 7.7 months with reduced toxicity compared with standard chemotherapy. Similarly, the bispecific T-cell-engaging antibody blinatumomab yielded a complete response rate of 44% and a median overall survival of 7.7 months in an extensively treated ALL population. Moreover, ∼80% of ALL patients in complete remission with evidence of minimal residual disease (MRD) achieved a complete MRD response following treatment with blinatumomab. These results highlight the tremendous promise of antibody-based treatment approaches for ALL. Ongoing and future research is critical to further define the role of the various immunotherapies in the frontline treatment of ALL. Additional challenges include the optimal sequencing of the available antibodies in the relapsed setting as well as their integration with stem cell transplant and chimeric antigen receptor T-cell therapy.

CD20 Expression and Response to Rituximab Treatment in B-Cell Precursor Lymphoblastic Leukemia - Results of the GMALL 08/2013 Trial

Introduction: Treatment with Rituximab has improved the outcome for patients with B-cell precursor ALL (B-ALL) and is conventionally restricted to patients with CD20 expression on leukemic blasts above a level of 20%. However, it is not known whether this arbitrary cutoff is biologically meaningful, or if also patients with lower CD20 expression levels profit from Rituximab treatment. In addition, CD20 expression levels might differ between different compartments and can change during early treatment. Therefore, in the current German Multicentric Acute Lymphoblastic Leukemia (GMALL) 08/2013 trial Rituximab is applied to all BCR-ABL1-negative B-ALL patients during induction and early consolidation irrespective of the initial blast CD20 expression. In this study, CD20 expression on blasts at diagnosis and after a 5-day dexamethasone prephase is thoroughly characterized and correlated to MRD response after induction I including one dose of Rituximab to evaluate its impact on response to Rituximab.Methods: Comparative quantification of CD20 expression levels was performed at diagnosis (blood and bone marrow (BM)) and at the end of the prephase (blood) and correlated to minimal residual disease (MRD) response after early Rituximab treatment. Samples were subjected to the EuroFlow standardized stain, lyse and wash and instrument setting procedures (van Dongen et al., 2012) and stained with a 3-tube, 8-color panel, containing the markers CD45, CD20, CD10, CD66c, CD3, CD19, CD71, CD9, CD13+33, CD34, CD22, CD11a, and CD38. CD20 median fluorescence intensities (CD20-MFI) as well as percentages of CD20+ B-ALL blasts among all blasts (%CD20+) were measured. MRD was quantified at day 22 after induction I using real-time quantitative PCR of clonal immune gene rearrangements. MRD response after induction was defined as MRD decrease to a level below 10-4, MRD persistence as detection of quantifiable MRD ≥10-4.Results: FCM results of a total of 166 samples of 84 B-ALL patients were evaluated. CD20 expression of circulating blasts significantly increased after a 5-day prephase in common/pre-B-ALL (c/pre-B) but not in pro-B-ALL in a cohort of 36 paired peripheral blood samples (Fig. 1 A-B, n=8 pro-B-ALL, paired t-test of CD20-MFI and %CD20: p=.1016 and p=.1660, Fig. 2 A-B, n=28 c/pre-B-ALL, p=.0029 and p=0.0060). Interestingly, the increase of CD20 expression on B-ALL blasts contrasted that on mature normal B-cells, where a decrease occurred in pro-B-ALL and c/pre-B-ALL samples at day 6 (paired t-test: p=.0485 and p<.0001, respectively) (Fig.1A, 2A).In 24 paired blood/BM pre-treatment samples the percentage of CD20+ blasts was significantly higher in blood in c/pre-B-ALL (n=19: paired t-test: p=.0009), but not in pro-B-ALL (n=5: paired t-test: p=.095) (Fig. 1C, 2C). The significance levels were not consistently reached for the comparison of CD20-MFI. Nevertheless, we show that in 3/24 (12.5%) patients the percentage of CD20+ B-ALL blasts in BM did not reach the arbitrary cutoff of 20% whereas the matching diagnostic blood did.Finally, CD20 expression levels from 25 BM and 30 pre-treatment blood samples and 38 blood samples after dexamethasone prephase from 54 patients were assessed (in total 93 samples). In further calculations we correlated MRD response values after one dose of Rituximab with the CD20 expression levels on blasts. In detail, the highest measured percentage value of %CD20 per patient in the group of MRD responders was compared to the highest measured %CD20 per patient in the group of MRD persisters. CD20 expression levels were significantly lower in 33 MRD persisters compared to 21 MRD responders (Fig 3, p=.0336). The difference was mainly attributable to a high frequency of MRD persisters in pro-B-ALL compared to c/pre-B-ALL (MRD persistence in pro-B-ALL 8/9 (89%) compared to 25/45 (56%) in c/pre-B-ALL).Conclusion: We measured significant differences in CD20 expression levels on leukemic blasts (i) between pre-treatment blood and BM and (ii) between pre-treatment blood and blood after prephase in patients with c/pre-B-ALL challenging the conventional eligibility criteria for the CD20 targeted treatment. MRD responders tended to have higher CD20 expression levels compared to MRD persisters. Extension of the patient cohort is ongoing to confirm this observation. Furthermore, we will analyze the impact of 3 rituximab applications after induction phase II. [Display omitted] DisclosuresRitgen:abbvie: Research Funding; Roche: Honoraria, Research Funding. Viardot:Gilead Kite: Consultancy, Honoraria; Roche: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Amgen: Consultancy. Kneba:Roche: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria. Goekbuget:Kite / Gilead: Consultancy; Celgene: Consultancy; Novartis: Consultancy, Other: Travel support, Research Funding; Pfizer: Consultancy, Other: Travel support, Research Funding; Amgen: Consultancy, Other: Travel support, Research Funding. Brüggemann:Incyte: Consultancy; Amgen: Consultancy, Research Funding, Speakers Bureau; PRMA: Consultancy; Affimed: Research Funding; Regeneron: Research Funding; Pfizer: Speakers Bureau; Roche: Speakers Bureau.

Minimal Residual Disease Response at End of Induction and during Maintenance Correlates with Updated Outcome in the Phase III GALLIUM Study of Obinutuzumab- or Rituximab-Based Immunochemotherapy in Previously Untreated Follicular Lymphoma Patients

Introduction: Minimal residual disease (MRD) status reflects depth of response and informs prognosis after first-line therapy in patients (pts) with follicular lymphoma (FL). In the GALLIUM study (NCT01332968), the primary endpoint of investigator (INV)-assessed progression-free survival (PFS) in previously untreated FL pts was significantly improved with obinutuzumab (GA101; G)- versus rituximab (R)-based immunochemotherapy treatment. We previously reported consistently higher MRD response rates with G- versus R-based treatment at the end of induction (EOI) (92% vs 85%, respectively; p=0.0041; Pott et al. ASH 2016). Here we report the correlation of MRD response at EOI with updated PFS data and the results of MRD response assessment during maintenance treatment and follow-up. We also assessed MRD responses and outcome in pts who remained MRD-positive at EOI. Methods: Previously untreated pts aged ≥18 years with FL requiring treatment were randomized 1:1 to receive 6-8 cycles of G (1000mg IV on days [D] 1, 8, and 15 of cycle [C] 1 and D1 of C2-6 or 8) or R (375mg/m2 IV on D1) plus standard chemotherapy (CHOP, CVP, or bendamustine). Responding pts received the same antibody as maintenance every 2 months for up to 2 years. MRD status was assessed by real-time quantitative (RQ)-PCR assays at mid-induction (MI) in peripheral blood (PB), at EOI in PB and bone marrow, at 4-monthly intervals during maintenance in PB, and at 6-monthly intervals during follow-up in PB, and was defined as negative (MRD response) if RQ-PCR and subsequent nested PCR were negative in all samples analyzed at the respective time point. INV-assessed PFS was estimated using Kaplan-Meier methods (data cut-off, February 12, 2018). Pts were included in the various analyses if they had evaluable MRD data and achieved a complete or partial response at EOI. Results: After 57 months9 median follow-up, MRD evaluable pts (n=634/1202 randomized FL pts) who had a MRD-negative response at EOI (n=564) continued to have a longer PFS than those who had a MRD-positive response at EOI (n=70; hazard ratio 0.38; 95% confidence interval 0.26, 0.56; p Conclusions: These data confirm the prognostic value of MRD status at EOI in previously untreated FL pts receiving immunochemotherapy. Analysis of MRD kinetics revealed that most of the pts who achieved MRD negativity at EOI sustained their responses during maintenance. The majority of pts who were MRD positive at EOI achieved MRD negativity during the first 4 months of maintenance. While this is likely to be indicative of the efficacy of continued treatment, it also suggests that response kinetics can be slower than in those pts who have an early MRD response at MI, and that responses that are beyond the sensitivity of the MRD assay may be less deep. Importantly, pts who failed to achieve MRD negativity at EOI or during early maintenance had a high chance of experiencing early progression or death. These data demonstrate the prognostic value of MRD response assessments in previously untreated FL pts receiving immunochemotherapy. Disclosures Hoster:F. Hoffman-La Roche: Other: Travel support, Research Funding; Roche Pharma AG: Other: Travel support, Research Funding. Unterhalt:F. Hoffman-La Roche: Other: Travel support. van der Jagt:F. Hoffman-La Roche Ltd: Employment, Honoraria, Research Funding. Janssens:Novartis: Membership on an entity9s Board of Directors or advisory committees; Roche: Consultancy, Membership on an entity9s Board of Directors or advisory committees, Other: Ad board, Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Sanofi-Genzyme: Speakers Bureau; Abbvie: Consultancy, Membership on an entity9s Board of Directors or advisory committees, Other: Ad board, Speakers Bureau; Janssen: Consultancy, Speakers Bureau. Kneba:Roche: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria. Mayer:Affimed: Research Funding; Roche: Research Funding; Johnson & Johnson: Research Funding; Eisai: Research Funding; Novartis: Research Funding. Pocock:Kent & Canterbury Hospital: Employment. Knapp:Roche: Employment. Danesi:F. Hoffmann-La Roche Ltd: Employment. Nielsen:F. Hoffmann-La Roche Ltd: Employment, Other: Ownership interests PLC. Brown:PAREXEL, external business partner with Roche Products Ltd, Welwyn, UK: Employment. Mundt:Roche: Employment, Other: Ownership interests PLC. Marcus:Gilead: Consultancy; F. Hoffman-La Roche: Other: Travel support and lecture fees; Roche: Consultancy, Other: Travel support and lecture fees . Hiddemann:Celgene: Consultancy, Honoraria, Membership on an entity9s Board of Directors or advisory committees, Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity9s Board of Directors or advisory committees, Research Funding; Bayer: Consultancy, Research Funding; F. Hoffman-La Roche: Consultancy, Honoraria, Membership on an entity9s Board of Directors or advisory committees, Research Funding.