P070 | ABSOLUTE LYMPHOCYTE COUNT AND IMMUNE TRANSCRIPTOMIC BONE MARROW PROFILE AS NOVEL PROGNOSTIC PREDICTORS IN PATIENTS WITH ACUTE MYELOID LEUKEMIA TREATED WITH INTENSIVE CHEMOTHERAPY

Background: In recent years the interest in bone marrow (BM) immune microenvironment (ME) of acute myeloid leukemia (AML) is emerging. Absolute lymphocyte count (ALC) is an independent prognostic factor in many cancers. In AML, enhanced ALC recovery after intensive chemotherapy (IC) has been associated with superior overall survival (OS). However, data correlating ALC recovery and immune prognostic factors in the novel mutational and therapeutic scenarios are lacking. Our study explores the immune transcriptomic variation in AML patients treated with IC and the prognostic impact of ALC. Results: We used a Pancancer Human NanoString panel on 48 BM samples collected from 35 AML patients (at diagnosis and after therapy). As for ALC, we evaluated 188 patients responsive to IC. All patients were assessed for minimal residual disease (MRD) after two courses. We defined 4 ALC time-points (TPs) after the start of induction course, with 500/mm3 as cut-off. Nanostring analysis showed significant differences in transcriptomic immune ME profile between diagnosis and post therapy with a specific focus on immune signature gene pathways (Fig.1) . Within the whole population, in patients treated with “3+7-based” regimen (51,6%), an association with OS was observed in patients with ≥500/mm3 ALC (31,9%) at day 15 (ALC-15) vs those under the cut-off (19,6%). This finding was further statistically significant in patients with ALC ≥500/mm3in all 4 TPs (25,5%) compared to those who had <500/mm3ALC in at least one TP (26%)(p=0.02). Considering patients who received allogeneic transplantation (alloT) (66%) vs those who did not (34%), patients in the second group with impaired ALC recovery had the worst OS, while those with normal ALC recovery had a better OS, similar to the transplanted ones.Lastly, among “3+7-based” patients who obtained MRD negativity (n = 52), a better ALC both in all TPs (n=29) and in ALC-15 (n=35) resulted in an OS advantage. Summary/Conclusion: ALC recovery can be a promising independent survival predictor in AML patients. It seems to emphasize an OS difference among MRD negative patients and may help identify patients who may benefit from alloT. A difference can be spotted when comparing BM onset samples analyzed with NanoString panel, according to ALC and MRD, but more extensive analysis is required.