The Cytogenetic Aberrations and Their Prognostic Value in 181 Untreated Patients with Lymphoplasmacytic Lymphoma/ Waldenström Macroglobulinemia in China

Background: lymphoplasmacytic lymphoma/ Waldenström macroglobulinemia (LPL/WM) is a rare B cell proliferative malignancy characterized by immunoglobulin M monoclonal gammopathy and /or bone marrow infiltration by lymphoplasmacytic cells. Cytogenetic aberrations are now the main prognostic predicators in some B-NHLs such as CLL. However, their prognostic valve in LPL/WM remains controversial and recurrently chromosomal abnormalities have rarely been reported. Furthermore, the genetic basis of LPL/WM in China is also unclear.

Methods: A panel of DNA probes was used to detect cytogenetic aberrations by fluorescence in situ hybridization (FISH), including RB1/D13S25 at 13q14, ATM at 11q22, TP 53 at 17p13, CEP12 and IGH translocation at 14q32, MYB at 6q23. Chromosomes were identified by G-banding and karyotypes were described according to the International System for Human Cytogenetics Nomenclature (ISCN, 1995). Totally, 181 untreated LPL/WM patients were enrolled in this study.

Results: The median age of 181 patients was 61 years (range 32-87). The male to female ratio was 2.75 (133/48). 90% and 15.7% patients showed an elevated serumβ2 microglobulin and LDH. The percentage of hepatomegaly, splenomegaly, lymphadenopathy and B symptom were 15.3%, 35.2%, 50% and 27.3%, respectively. Almost half patients were in the high risk ISSWM group. The chromosomal karyotypes were successful in 153/181 (84.5%) cases, of which 15 patients showed clonal abnormalities. 8 of the 15 patients with abnormal chromosome were complex. The main aberrations of chromosomal karyotypes were 6q deletion (3/15, 20%), and loss of sex chromosomes (3/15, 20%). The other abnormalities include trisomy 12, trisomy 4, trisomy 3, 20q deletion, 17p deletion and so on. All the 6q deletions patients were in the complex karyotype group. Moreover, the trisomy 12 detected by FISH were always accompanied with chromosomal karyotypes abnormalities. Of 181 patients, 139 patients had FISH detection, of which 25 patients (18%) had FISH abnormalities. The most common aberrations were 6q deletion (6/28, 21.4%), trisomy 12 (5/59, 8.5%), 17p deletion (8/131, 6.1%). 13q deletion, gain 1q21and 11qdeletion were 4.6% (6/130) and 2.8% (3/36) and 2% (2/99), respectively. About 5.4% (7/130) patients had IGH gene translocation. Although it was higher in our study, this aberration always accompanied with other clones. Besides, 17p deletion was also more frequent in complex clone group, while trisomy 12 was more common in the single clone group. In LPL/WM, the chromosomal abnormities was an adverse predictor for both progress-free survival (PFS) and overall survival (OS). The median PFS and OS for patients with this abnormity was 62 months (62m vs 69m, p=0.022) and 75 months (75m vs 109m, p=0.033), which was significantly higher than normal patients. In different FISH groups, only TP 53 deletion had a poor effect on both PFS and OS in LPL/WM patients. The median PFS and OS were significantly shorter than those without the abnormality (median PFS 34m vs 77m, p=0.008; median OS 34m vs 135m, p=0.006). However, the 6q deletion and trisomy 12 did not significantly influence both PFS and OS. In addition, we found that the number of different clones had an effect on the survival of patients. The complex clone group showed shorter PFS and OS than the single clone group (p<0.05).

Conclusion: Although the detection of cytogenetic aberration is rare in Chinese patients, it plays an essential role in diagnosis and prognostication.