The Role of Molacular Genetic Examination in Differential Diagnosis and Prognostic Prediction in Patints with B-Cell Chronic Lymphoproliferative Disorders: A Restrospective Study of 1592 Patients

Background: B-cell chronic lymphoproliferative disorders (BCLPD) are a heterogeneous group of mature B-cell malignancies characterized by monoclonal proliferation in the bone marrow (BM) or peripheral blood (PB). The overlapped clinical features and the lack of individual diagnostic markers make diagnosis challenging, especially in patients who have difficulty to get adequate non-BM biopsy specimens or patients manifest as leukemic onset without nodes-involvement. It is necessary to explore novel methods to make precise diagnostic classification and prognostic prediction through simply PB/BM examination.

Methods and results: A total of 1592 patients with newly diagnosed BCLPD were enrolled from January 1998 to December 2016, of which chronic lymphocytic leukemia (CLL) accounted for 39%, leukemic marginal zone lymphoma (l-MZL)occupied 13%, and Waldenstrom's macroglobulinemia/ lymphoplasmacytic lymphoma (LPL/WM), leukemic follicular lymphoma (l-FL) and mantle cell lymphoma (l-MCL) were 13%, 9% and 8%, respectively. There are 14% patients failed to fit into any of the categories and remaining unclassified which defined as BCLPDU. The median age at diagnosis was 58 years old. The male/female ratio of all BCLPD patients was 1.84:1. Male predominance was pronounced in WM/LPL, l-MCL and HCL with a M/F ratio of 2.5-2.7, while with balance gender in l-MZL and l-FL.

FISH analyses were performed in 1234 patients. 17p and 11q deletion were most common in l-MCL (36% and 17%), while 13q deletion and trisomy 12 were most frequent in CLL (35% and 21%). Patients with 17p deletion showed significantly adverse survival in CLL and l-MCL (p<0.05), but the phenomenon was not found in other types of BCLPD. Instead, complex karyotype showed better predictive capability of worse survival than 17p deletion in patients with l-FL, l-MZL and BCLPDU.

A total of 665 patients had been successfully amplified the IGHV-IGHD-IGHJ rearrangements. Based on a cut-off value of 98% homology, the IGHV mutated proportion in patients with l-MCL was 48.6%, which was higher than other BCLPDs, following CLL 33.3% and l-MZL 28.6%, while most of WM and l-FL were unmutated. The most frequent rearrangement in l-MZL were IGHV1-2*01, which was seldom found in other subtypes. Also, DH2-2 and VH3-7 were mainly found in CLL and l-MCL respectively. Besides, we have identified several stereotyped IGH CDR3 which were specific for the certain BCLPD subtype. About 23% unclassified patients could acquire further diagnosis according to the special mutation status, VDJ rearrangements or stereotyped CDR3 sequencing.

With a median follow-up of 50.3 months, 522 patients (38.0%) had disease progression or died. Patients with lMCL have a significant worse survival than other entities, with a 3-year overall survival (OS) rate of 58%. Following , patients with WM/LPL had relatively poorer prognosis with a 5-year OS rate of 68.2%, while the prognosis for l-MZL, l-FL and CLL were relatively favourable, with a 5-year OS of 80%.The OS of the B-CLPD had improved over time due to the emergence of immunotherapy and novel (3-year OS improved from 82.1% to 92.2%). The improvement of l-MCL and WM was obvious but not for CLL and l-MZL.

Conclusion: Non-BM biopsy specimens are not available for part of BCLPD patients. Overlapped magnification of BM/PB brings on difficulties in differential diagnosis. Besides morphology and immunophenotype, comprehensive analysis of FISH, karyotype, IGHV, MYD88 or BRAF mutation and other molecular examination might contribute to further differential diagnosis and prognostic prediction. Moreover, it might provide advice for the initial time and strategy of treatment.