Pretreatment Patient Characteristics Associated with Achieving Bone Marrow Minimal Residual Disease-Free Status with Frontline Fludarabine, Cyclosphosphamide, Rituximab (FCR) Chemoimmunotherapy for CLL,
Authors: Wierda William G. , O'Brien Susan , Ferrajoli Alessandra , Koller Charles Asa , Burger Jan A. , Faderl Stefan , Garcia-Manero Guillermo , Kadia Tapan , Lerner Susan , Keating Michael J 
Published: October 2019

Abstract
Abstract 3902
Chemoimmunotherapy (CIT) is highly effective treatment and standard of care for patients (pts) with CLL. Response to treatment by NCI-WG/IWCLL criteria correlates with outcome; pts who achieve complete remission (CR) have superior progression-free and overall survival compared to pts who achieve partial remission (PR); and pts who fail therapy have the poorest outcome. Emerging data indicate improved outcomes for pts who achieve minimal residual disease (MRD)-free status in blood or bone marrow (BM) by end of treatment. We are conducting a clinical trial to prospectively evaluate pretreatment pt characteristics and prognostic factors and correlations with NCI-WG response, MRD-free status, and time to event outcomes with standard frontline fludarabine, cyclophosphamide, and rituximab (FCR) CIT.
A total of 197 pts have been registered, 160 have completed treatment and are evaluable for response by NCI-WG criteria, and 127 have BM MRD status evaluated by standard 4-color flow cytometry at Course 3 and/or end of treatment. We report on pretreatment characteristics associated with MRD-free status at end of treatment. For the 160 pts evaluable for response by NCI-WG criteria, 63% were male; the median (range) age, β2M, and absolute lymphocyte count (ALC) were 58 yrs (38–84), 3.6 mg/l (1.3–14.1), and 78.7 K/μl (.8–394), respectively. The percent pts with Rai high-risk disease, unmutated IGHV status, ZAP70+ by immunohistochemistry (IHC) and CD38+ (30% cutoff) was 35%, 60%, 63%, and 37%, respectively. According to the hierarchical categorization, FISH demonstrated 17p del in 9%, 11q del in 18%, +12 in 17%, 13q del in 36%, and no abnormality in 20% of pts. The median number of FCR courses given was 6; 57% received all intended 6, 21% received 4–5, and 23% received ≤3. Of the 160 pts, 63% achieved CR, 12% nodular PR (nPR), 23% PR and 3% did not respond. Of 127 pts with BM evaluated by 4-color flow cytometry at end of treatment, 56% were MRD-free. Of 71 MRD-free pts, 27 were negative at end of course 3, 33 converted to negative after course 3, and 11 were negative at end of treatment but did not have a course 3 evaluation. Univariable Chi-square analyses demonstrated pretreatment β2M, IGHV mutation status, 17p del, and +12 correlated with MRD-free status at end of treatment (Table). The following did not correlate: age, Rai stage, WBC, ALC, HGB, PLT, ZAP70, CD38, or number of FCR courses received. Multivariable logistic regression model identified β2M≥4 mg/l (odds ratio=.78; p=.007) and unmutated IGHV (odds ratio=.77; p=.006) as independently associated with lower likelihood to achieve MRD-free status.
In conclusion, mutated IGHV and β2M <4 mg/l are independently associated with increased likelihood of achieving MRD-free status with frontline FCR CIT; further follow up is needed to correlate MRD-free status with improved survival outcomes for patients treated on this trial.TableNCI-WG Responsen% MRD-NegativeCR8071nPR150PR3047*NR20Pretreatment Characteristicn% MRD-Negativep-valueAge (yrs) <65100600.07≥652741Rai Stage Low & Int-risk82610.12High-risk4347b2M (mg/l) <473640.02≥44942ALC (K/ml) <5040560.86≥508755IGHV Mutated47700.006Unmutated6244ZAP70 IHC Negative41610.28Positive7351CD38+ ≤7%4863Ref**8–29%27480.23≥30%42550.46FISH 13q del4556RefNone22680.32+1220800.0611q del20400.2417p del10200.04*All MRD-free are PR due to cytopenia, with no evidence of CLL**Used as reference or comparison group

Disclosures:
No relevant conflicts of interest to declare.