CD36-positive B-lymphoblasts Predict Poor Outcome in Children With B-lymphoblastic Leukemia.

Objective: We observed that pediatric patients with B lymphoblastic leukemia which expressed CD36 at diagnosis seemed to have worse outcome than patients whose blasts did not. Here, we describe the patient, disease characteristics, pathological, molecular, and genetic features and outcomes of patients with CD36+ B-LL compared to patients with CD36- B-LL. Methods: We retrospectively reviewed all flow cytometry reports from September 2008 to December 2015 to identify patients diagnosed at our institution with CD36 expression on B lymphoblasts. CD36-control patients were chosen from our leukemia database and matched 2: 1 to CD36+ patients for National Cancer Institute (NCI) risk group at diagnosis. We reviewed diagnostic marrow slides for cytoplasmic granules and abstracted clinical data from patient charts. To identify underlying genetic abnormalities, clinical FISH testing and RNA sequencing was performed on 5 of our CD36+ patients, and RNA-seq data from the NIH Therapeutically Applicable Research to Generate Effective Treatments (TARGET) ALL Expansion Phase 2 data set were examined. Results: Twenty-five of 366 (6.83%) patients diagnosed at our institution in the study period had CD36+ blasts. With a median follow-up of 5.32 years, 5-year event-free survival (EFS) and overall survival (OS) were significantly worse for CD36+ patients compared to CD36- patients who were NCI Standard Risk at diagnosis (EFS: 60% +/- 15.49 vs 95% +/- 4.87, P=.016; OS: 90% +/- 9.5 vs 100%, P=.019). NCI Standard Risk patients whose blasts were both CD36+ and had granules had the worst survival compared to CD36- patients without granules (EFS 25% +/- 21.65 vs 95% +/- 4.87, P=.0004). From our CD36+ patients and the TARGET database, we found 2 ABL2 mutations, 1 PDGFRB mutation, and 2 NRAS mutations. Conclusions: For NCI Standard Risk patients, CD36 expression on B-lymphoblasts identifies patients with B-LL who have especially poor outcome. This may be due to underlying genetic abnormalities that may be amenable to targeted therapy.