Cytogenetic Abnormalities in B-CLL at Binet Stage A: Overview in a Cohort of 484 Untreated Patients and Relations with the ZAP-70 and IgVH Mutation Status.

Since January 2004, the French Ministry of Health supports a multicentric study aimed at detecting biological prognostic markers in B-CLL at Binet stage A, able to identify those patients in early clinical disease stage who will progress to a more advanced disease requiring early therapy. These include: 1/ detection by FISH of prognostically relevant cytogenetic abnormalities [trisomy 12, deletions of the ATM and P53 genes, and deletions at chromosomal band 13q14], 2/ cytoplasmic expression of ZAP-70 and CD38 by flow cytometry, 3/ IgV_H gene analysis, and 4/ serum concentration levels of sCD23 and thymidine kinase. 550 patients from 10 institutions are currently enrolled in this study, 331 men and 219 women, with a median age at the time of diagnosis of 66 years (ranged from 26 to 100).

To date interphase cytogenetic analyses by FISH have been carried out in leukemic cells of 484 patients using commercially available probes. For deletions, results are scored as A, B or C depending on the % of deleted lymphocytes [A = <5 (negative), B = 5–20, C = >20–100)]. The distribution of the prognostically relevant cytogenetic abnormalities is as follows: 63.6 % (n = 308) 13q14 deletions, 12.6% (n = 61) trisomies 12, 11.1% (n = 54) ATM gene deletions, and 16.6 % (n = 81) P53 gene deletions, all equally shared between men and women subgroups. Conventional cytogenetics (CC) have been performed in 391 out of the 484 patients. Results of the two techniques (FISH/CC) are highly discordant for detection of 13q-, 11q-, and 17p- deletions, respectively observed in 8.8 %, 3.6%, 4.4% of our cases by CC, and quite similar for detection of trisomy 12 (9.8% by CC). Nevertheless, FISH/CC discordance disappears for 11q- and 17p- detections when only FISH results from the C group are taken into account (5.7%, 4.3% deleted cells, respectively, in C group), showing the power of FISH to detect minor 11q- and 17p- clones in B-CLL at Binet stage A. In addition, CC detect abnormal karyotypes in 38.6 % of cases, including recurrent numerical abnormalities [21% (n=32) involving chromosome X, 3.3% chromosome 19], and structural rearrangements (5.3% at 14q32, and 3.9% 6q deletion). 15.9% of abnormal karyotypes (n = 24) are complex.

IgV_H gene analyses have been performed in 301 patients. As expected, adverse prognostic genetic markers [ATM and P53 deletions, trisomy 12] are significantly more frequent in cases with unmutated IgV_H sequences (n = 83) as compared to mutated cases (n = 218) [χ ² tests: P < 0.0001, P = 0.008, and P = 0.0004, respectively]. On the contrary, the prognostically favorable 13q14 deletion is more frequent in cases with mutated IgV_H status [χ ² test: P = 0.0002]. Comparison with the ZAP-70 status, analyzed by flow cytometry, shows less clear distributions of ATM and P53 deletions, trisomy 12 and 13q deletion, between the ZAP-70 + (n = 112) and ZAP-70 - (n=209) subgroups [χ ² tests: P < 0.008, P = 0.32, P = 0.046, and P = 0.048, respectively]. By May 2006, this ongoing study designed for 700 patients should provide very helpful data on laboratory parameters important in the management of untreated B-CLL at Binet stage A.