Central nervous system (CNS) involvement has an adverse impact on survival in newly diagnosed adult acute lymphoblastic leukemia (ALL) assessed by flow cytometry, Leukemia & Lymphoma,

Introduction: "Philadelphia like" ALL has been related to poor prognosis. CRLF2 over-expression (cytokine receptor like factor-2) has been found in up to 50% of patients with Philadelphia-like ALL and its expression can be measured by Flow Cytometry (FC). CRLF2 over-expression is more common in Hispanic population (45-68%) however, there is no current recommendation in using it as a prognostic marker. Objectives: Find the prevalence of CRLF2 overexpression measured by FC, in adult Mexican patients with treatment-naïve ALL Describe the outcomes of the patients who over-expressed CRLF2 by Complete Response (CR), Minimal Residual Disease (MRD), Leukemia-Free Survivale (LFS) and Overall Survival (OS). Methodology: This is a retrospective cohort study in adults with newly diagnosed ALL from two reference centers in Mexico City. We measured CRLF2 expression by FC in fresh bone marrow samples from treatment-naïve patients at one location; to define over-expression, samples were first analyzed by two different experts who grouped the cases in over-expression or no overexpression using Mean Fluorescence Intensity (MFI) between two populations, blasts and controls (normal B cells). Outcomes were compared using chi-square test for binary variables and log-rank test for time-to-event variables with a p value <0.05 as significant. Results: From April 2018 to January 2020 46 patients with treatment-naïve B-cell ALL were evaluable; the median age was 29.5 years, 38 (82.6%) were Adolescents and Young Adults (AYA), 22 (47.8%) had leukocytosis, 15 (53.5%) of the evaluable karyotypes, were assigned to high-risk group. The median time of follow-up was 24.5 months and 19 (41.3%) patients were positive for CRLF2-overexpression. For the follow-up cohort all of the patients were evaluable for outcomes. CNS disease was detectable in 11(24.5%) patients which was higher in CRLF2-overexpresed patients (15.5% vs 8.9%, p=0.015). We found no difference in Complete Remission (CR) in CRLF2 status but a high tendency for R/R (Relapse/Refractory) disease (83.3% in CRLF2-overexpression vs 60% in CRLF2 negative group; p=0.09) and dead (63.2% in CRLF2-overexpression vs 37% in CRLF2 negative group; p=0.07). MRD1, 2 and 3 (1=after induction, 2= week 16 and 3= before maintenance) was significantly worse in patients with CRLF2 overexpression (1=15.8% vs 58.3%, p<0.01; 2=7.1% vs 52.6%, p<0.01; 3=0% vs 55.6%, p<0.05). Overall Survival was significantly worse in patients with CRLF2 overexpression (Median Not Reached vs 11.05 months; p=0.04) (Figure 1); Disease-Free Survival (DFS) had a tendency towards worse outcome in patients with CRLF2 overexpression (18.48 vs 5.82 months, p=0.07) (Figure 2). Conclusion: Survival in patients who have CRLF2 overexpression is significantly worse when measured by FC, this might be related to early high-risk markers as MRD. CRLF2 overexpression in this hispanic sample was higher (41%) than other reports. CRLF2 measured as a prognostic factor by FC needs to be further considered due to the high availability of this technique across Latin-America. Figure 1 Figure 1. Disclosures Rangel-Patiño: Abbvie: Speakers Bureau; Bristol: Consultancy. Espinosa: Pfizer: Consultancy; Amgen: Speakers Bureau; Janssen: Consultancy. Demichelis: Novartis: Consultancy, Research Funding, Speakers Bureau; Gilead: Consultancy; Bristol/Celgene: Consultancy, Speakers Bureau; Jazz: Consultancy; ASH: Research Funding; Astellas: Consultancy; AMGEN: Consultancy, Speakers Bureau; Abbvie: Consultancy, Speakers Bureau.

Introduction: Several studies published in recent years dealing with the detection of Central Nervous System (CNS) disease in Acute Lymphoblastic Leukemia (ALL) have demonstrated superiority in terms of sensitivity of Flow Cytometry (FCM) over standard cytology (Tawfik et al, 2018). However, whether CNS activity detected by FCM has an impact on the clinical outcome of ALL adult patients, is still a matter of debate. (Del Principe et al, 2019) Methodology: We analyzed a retrospective cohort of newly diagnosed ALL adult patients in an oncologic center in Mexico, who had a CNS analysis by FCM and conventional cytology, diagnosed between 2017 and 2019. The primary endpoint was to assess the impact on the survival of patients with CNS disease detected by FCM. We defined positive FCM (FCM+) when the patient had >10 phenotypically pathologic events and positive cytology (Cyt+) when the patent had confirmed CNS-2 or CNS-3 activity as defined by NCCN and ESMO; double-negative (DN) patients were considered when neither FCM nor cytology demonstrated disease as described above. Baseline characteristics were grouped in tables and summarized as medians and ranges for quantitative variables or frequencies in qualitative variables. Basal characteristics and different outcomes were compared by the chi-square test for binary variables, and the Mann-Whitney U test for quantitative variables. Overall Survival (OS) and Disease-Free Survival (DFS) analysis were made by Kaplan-Meier curves. A comparison between groups was performed using the log-rank test, with a significant P value less than 0.05 and a 95% confidence interval (CI). We performed a Cox regression model to obtain an HR with a 95% confidence interval for survival to identify risk associations. Results: Of the 92 evaluable patients, the median age was 28 years. 88% of all ALL were ALL-B. The median count of leucocytes was 11.65 x109/L (range 4.71-38.24 x109/L); median LDH was 758 UI/L (range 314-1242 UI/L). 63% of patients had an unfavorable karyotype (hypodiploidy, complex karyotype, or KMT2A). At diagnosis, 27 (28%) were positive by FCM and negative by cytology. The median of the analyzed events was 14,733 (5,025-50,000) with a viability of 38.5% (22-61.75). Only 6 patients were positive by both techniques. 45% of patients with CNS involvement had neurological symptoms (mainly headache). The most used treatment was BFM in 56.7% of patients, followed by HyperCVAD in 37.8%. Patients with documented CNS infiltration by FCM or cytology were treated with triple intrathecal chemotherapy two times per week. Three patients had no response after two weeks of treatment, one received radiotherapy without any response and the other two were dead for chemotherapy toxicity. We found gender as the only statistically significant variable associated with a higher FCM+ (77% males vs 23% females, p<0.01). For the entire cohort, the complete remission (CR) after induction was 84% and 63% had a negative minimal residual disease (MRD) by FCM in the bone marrow. 15% of the patients were refractory. There were no differences between CR (73% versus 88%, p= 0.16), MRD negativity (46% versus 69%, p=0.11), refractory disease (26% versus 10%, p=0.13) or relapsed disease (50% versus 43%, p=0.65) between FCM(+) and ND groups. The OS for the entire cohort was 11.3 months. Patients with FCM+ had a lower survival of 5.6 months [CI95% (0.72-10.67)] compared with 11.8 months [CI95% (0.47-11.95)] in the DN group. The median DFS for the FCM+ patients was 4.6 months [CI95% (3.42-5.92)] versus 16.4 months [CI95% (6.21-26.75)] for DN group. In the Cox regression model, the HR for survival in patients with FCM+ was 1.85 (CI95% 1.004-3.421; p=0.04). Conclusions: Despite the retrospective nature of this study, the detection of CNS involvement was increased from 6% to 28% employing FCM compared with cytology. As mentioned previously, in other studies, FCM has greater sensitivity than cytology (Ranta et al. 2014). According to our results, the presence of CNS disease, detected by FCM has an adverse impact on OS in adult patients with newly diagnosed ALL. These results dictate consideration of FCM as a routine study in the diagnosis of ALL. Prospective studies are needed to evaluate more intensive treatment in these patients. Figure Disclosures No relevant conflicts of interest to declare.