PB2141: CLINICOPATHOLOGICAL FEATURES AND OUTCOME OF CD5 POSITIVE DIFFUSE LARGE B CELL LYMPHOMA AND THE SIGNIFICANCE OF CD5 EXPRESSION STRENGTH: 10-YEAR SINGLE CENTER EXPERIENCE

Abstract

Background: CD5 positive (CD5+) diffuse large B cell lymphoma (DLBCL) is a rare subtype of DLBCL encompassing 5-10% of patients (pts) with DLBCL, and it is characterized by poor outcome. Aims: To identify clinicopathological features of CD5+ DLBCL in a cohort of pts managed at Clinic for Hematology, Clinical Center of Serbia during a 10-year period (2012-2021). Methods: We retrospectively analyzed immunohistochemistry (IHC) results of biopted tumor tissue of 537 pts with DLBCL NOS. Survival analysis was performed using Kaplan-Meier method and log-rank test. Results: Out of a total of 537 pts, in 211 (39.3%) CD5 was not analyzed by IHC, while in the remaining 326 (60.7%) was. Among them, 27 (8.3%) were found to be positive for CD5, out of which 10 pts were designated at the pathology report as CD5 +/- (5 pts) or CD5 -/+ (5 pts), while the rest 17 pts were clearly CD5+. In CD5 positive cohort, 52% of pts were men and median age at diagnosis was 63 years. ECOG performance status (PS) was poor (≥2) in 8 (29.6%) pts. One third of pts had advanced stage disease (Ann Arbor III/IV), while the rest two thirds were limited stage (I and II). Eleven out of 26 pts (42.3%) presented with B symptoms, 3/26 (11.5%) expressed bulky disease, while two thirds presented with extranodal disease. More pts (13/23 or 56.5%) were of nonGCB subtype according to IHC, while 4 out of 11 pts (36.4%) analyzed for c-myc protein expression were double expressors. Median Ki-67 proliferative index was 80%. Almost half of pts (47.6%) had increased initial lactate dehydrogenase (LDH) activity, while median beta-2 microglobulin (b2m) level was 3.38 mg/L. Nine out of 26 pts (34.6%) were IPI>2, while the rest 17 pts were IPI 0-1. Vast majority (25/27, 92.6%) were treated with chemoimmunotherapy in the first line, most of them with anthracycline-based protocols, 1 patient received cyclophosphamide, vincristine, prednisone (COP), and 1 patient succumbed before treatment commencement. Among treated pts with known outcome after first line, 18 (72%) pts achieved complete remission, 4 (16%) achieved partial response, while 3 (12%) pts did not respond to treatment. Median progression-free survival (PFS) after first treatment line for all pts in CD5 positive cohort was 25 months (95%CI 13.76-36.24), while median overall survival (OS) was not reached. Age at diagnosis, presence of B symptoms, and extranodal disease did not significantly influenced PFS and OS. Patients with bulky disease, nonGCB subtype, and double expressors experienced significantly shorter PFS (p=0.03, P=0.043, and p=0.025, respectively), but these features did not impact OS. On the other hand, b2m levels >3.38 mg/L, LDH >1x upper limit normal, and IPI >2 were significantly associated with shorter OS (p=0.014, p=0.01, and p=0.015, respectively), while they were not significant regarding PFS. ECOG PS >1 was significantly associated with both poor PFS and OS (p=0.005 and p=0.002, respectively). Intrestingly, pts designated as CD5+ at pathology reports experienced median PFS of 20 months in contrast to 52 months in pts descripted as CD5+/- and CD5-/+ (p=0.021). However, the difference between these two subgroups regarding OS was not observed. Summary/Conclusion: In our CD5+ DLBCL cohort, bulky disease, nonGCB, and double expressors were associated with shorter PFS, higher b2m, LDH, and IPI correlated with shorter OS, while higher ECOG PS was associated with shorter both PFS and OS. Median PFS after 1st treatment line was around 2 years, while median OS was not reached. Strenght of CD5 expression was significantly associated with PFS. CD5 should be mandatory within IHC for DLBCL.