Incidence of Cytogenetic Abnormalities in Newly Diagnosed Binet Stage A B-CLL and Relationship with Prognostic Biomarkers: Preliminary Results On 305 Patients Included in the Prospective O-CLL1 GISL Study

Background. The clinical heterogeneity of chronic lymphocytic leukemia (CLL) requires parameters to stratify patients into prognostic subgroups to adapt treatment ranging from ‘watch and wait’ to allogeneic stem cell transplantation. To this end, several parameters such as lymphocyte doubling time, β-2 microglobulin, CD38 and ZAP-70 expression, immunoglobulin variable heavy chain (IgVH) mutation status and genetic abnormalities, as assessed by fluorescence in situ hybridization (FISH), have been integrated in clinical practice. Aims. In the present study, we investigated by FISH the incidence of the known major cytogenetic alterations (+12 and 13q14, 17p13, 11q23 deletions) in a series of Binet A B-CLL patients included in the prospective O-CLL1 GISL study started in April 2007. Methods. Molecular markers characterization and FISH analyses were performed as previously reported (Cutrona et al. Haematologica, 2008; Fabris et al. GCC, 2008). A cut-off value of 2% was used to distinguish mutated and unmutated patients. CD38 and ZAP-70 were determined by flow-cytometry and a 30% cut-off was used to distinguish between positive or negative cases. Results. Up to date, 326 patients have been enrolled in the trial and FISH data concerning trisomy 12 and 13q14, 17p13, 11q23 deletions were available in 305 patients. At least one abnormality was found in 197 (64%) cases. The most frequent was del(13)(q14) (150/305, 49%), followed by +12 (40/303, 13%) (in one and three cases accompanied by 17p13 and 13q14 deletions, respectively), del(17)(p13) (7/305, 2%) and del(11)(q23) (17/305, 5%). 13q14 deletion was found as a sole abnormality in 134 patients; in the remaining cases, it was combined with +12 (3 pts) and 17p13 (3 pts) or 11q23 (10 pts) deletions. Among patients with 13q14 deletions, 99 were monoallelic, 12 biallelic and 39 showed a combination of the two patterns. Biomarkers data were available in all of the patients: 95/305 (31%) cases had unmutated IgVH genes; ZAP-70 and CD38 were positive in 117/305 (38%) and 72/305 (23%) cases, respectively. Concerning the distribution of cytogenetic aberrations, the unmutated IgVH group included 29/150 (19%) 13q14 deleted cases, 23/40 (57%) cases with trisomy 12 and 4/7 (57%) and 16/17 (94%) with 17p13 and 11q23 deletions, respectively. ZAP-70-positive groups included 43/150 (28%) 13q14 deleted cases, 26/40 (65%) cases showing trisomy 12 and 5/7 (71%) and 12/17 (70%) with 17p13 and 11q23 deletions, respectively. Finally, CD38-positive cases included 18/150 (12%) 13q14 deleted cases, 26/40 (65%) cases carrying trisomy 12 and 5/7 (71%) and 7/17 (41%) with 17p13 and 11q23 deletions, respectively. The percentages of IgVH mutations significantly correlated with cytogenetic alterations; namely, 5.8±0.3 for cases with del(13)(q14), 4.6±0.4 for normal karyotype, 2.6±0.5 in +12, 0.3±0.2 in del(11)(q23), and 1.7±0.9 in del(17)(p13) cases (p for trend <0.0001). A significant correlation was also found for ZAP-70 expression: namely 32±1.8 for cases with del(13)(q14), 38.6±2.2 for normal karyotype, 47.6±3.7 for +12, 55.8±7.0 for del(11)(q22) and 42.4±11.7 for del(17)(p13) (p<0.0001). Similarly, CD38 percentages were (mean value ± sem) 9.3±1.7, 16.9±2.1, 52.9±5.7, 26.8±6.2, 37.0±12.7 for del(13)(q14), normal karyotype, +12, del(11)(q23) and del(17)(p13) alterations, respectively (p for trend <0.0001). Finally, cytogenetic abnormalities were clustered in 3 risk groups [i.e. low del(13)(q14) and normal; intermediate (+12); and high risk del(11)(q23) and del(17)(p13)] and significantly correlated (p<0.0001) with a scoring system in which cases were stratified in 4 different groups according to the absence (group 0) or presence of 1 (group 1), 2 (group 2) or 3 (group 3) biomarkers (Morabito et al., BJH, 2009, voce). Interestingly, 147/154 cases scoring 0, gathered in the low FISH group, whereas 17/22 high FISH risk cases clustered in scoring 2-3. Conclusions. Our preliminary results indicate that in Binet stage A B-CLL patients at diagnosis cytogenetic abnormalities with an expected negative clinical impact are relatively few (7.2%) but significantly associated with prognostic biomarkers which negatively predict the clinical outcome in B-CLL.