Tehran University of Medical Sciences International Journal of Hematology-Oncology and Stem Cell Research 2008-2207 17 1 2023 01 16 39 47 Aysun Senturk Yikilmaz Department of Hematology, Bilkent City Hospital, Yıldırım Beyazıt University, Ankara, Turkey Şule Bakanay Department of Hematology, Bilkent City Hospital, Yıldırım Beyazıt University, Ankara, Turkey Duygu Avcı Department of Hematology, Ankara Numune Training and Research Hospital, , Ankara, Turkey Sema Akinci Department of Hematology, Atatürk Training and Research Hospital, Ankara, Turkey Mesude Falay Department of Hematology, Ankara Numune Training and Research Hospital, , Ankara, Turkey Gülsüm Özet Department of Hematology, Ankara Numune Training and Research Hospital, Ankara, Turkey İmdat Dilek Department of Hematology, Atatürk Training and Research Hospital, Ankara, Turkey 2021 06 08 2021 09 06 Background: The transmembrane receptor tyrosine kinase-like orphan receptor 1 (ROR1) has acted on the causation and sustentation of mature B cell lymphomagenesis for chronic lymphocytic leukemia (CLL) cells. The aim of this study was to show whether there is a relationship between the level of ROR1 surface expression in CLL cells and disease findings. Materials and Methods: The level of ROR1 cell surface expression was determined in accordance with the flow cytometric analysis of CLL patients at the first diagnosis time.  2 groups were formed according to the high and low ROR1 levels. The cut-off point to the ROR1 level was calculated for advanced-stage disease by using receiver operating characteristic (ROC) curves. A two-sided p-value <0,05 was considered statistically significant. Results: 108 CLL cases with a median age of 60 were enrolled. The median percentage of ROR1 cell surface marker positivity in the CD5/CD19 positive leukemic cell was 62%. The CLL cases with high ROR1 levels have thrombocytopenia (p=0.042), anemia (p=0.028), and high beta 2 microglobulin value ≥3 mg/dL (p=0.002) and the need for first-line treatment (p=0.043). Conclusion: The poor prognostic parameters such as splenomegaly, anemia, higher beta 2 microglobulin levels, intermediate/advanced RAİ stage disease, and need for first-line treatment had associated high-level ROR 1 expression of our CLL patients. It needs to be investigated for its effect on predicting disease burden and aggressiveness with more comprehensive studies on ROR1 expression levels in CLL cases. https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/view/1649 https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/download/1649/961