Chronic Lymphocytic Leukaemia Patients with a Biallelic Deletion of 13q14 Have a More Favourable Profile of Prognostic Factors Compared with Cases That Have a Monoallelic 13q14 Deletion.

Deletion of 13q14 is a common finding in CLL and is associated with a good prognosis when it occurs in the absence of del 17p13, del 11q23 and trisomy 12. In contrast, the latter chromosomal abnormalities, together with unmutated IgVH genes, CD38 expression and p53 dysfunction, are associated with an adverse clinical outcome. Unlike del 17p13 and del 11q23, which usually affect only one allele, del 13q14 can affect one or both alleles in a given case. It was therefore of interest to compare cases of CLL harbouring a monoallelic 13q deletion (13q+/−) with those cases harbouring a biallelic 13q deletion (13q−/−). FISH data including 13q14 status were available for 103 newly diagnosed cases of CLL presenting to the Royal Liverpool University Hospital between March 2002 and June 2005. 18 cases had a biallelic 13q deletion and 32 had a monoallelic 13q deletion, while 53 cases had no 13q deletion (13q+/+). As compared with 13q+/− and 13q+/+ cases, 13q−/− cases had a lower frequency of unmutated IgVH genes (8% v 32% and 46% respectively), CD38 positivity (14% v 32% and 29%), p53 dysfunction (13% v 34% and 30%), deletion of 17p13 (0% v 9% and 8%), deletion of 11q23 (0% v 13% and 6%) and trisomy 12 (0% v 13% and 23%). The combined frequency of 17p deletion, 11q deletion and trisomy 12 among cases with 13q−/−, 13q+/− and 13q+/+ was 0%, 31% and 35% respectively (P = 0.0085). At least one of the above adverse prognostic factors was found in 33% of 13q−/− cases, 82% of 13q+/− cases and 80% of 13q+/+ cases (P = 0.0084). There was no difference in sex or clinical stage between the 3 groups, although patients with 13q−/− tended to be older than those with 13q+/− (68.1 v 61.3 years, P = 0.0720). After a median follow-up of 18 months (range 1–39 months), no difference in treatment-free or overall survival was observed between the 3 groups but only 7 of the 50 evaluable patients had received treatment and only 3 had died. In conclusion, CLL patients with biallelic deletion of 13q14 appear to have a more benign form of the disease than do patients with a monoallelic 13q deletion. The latter have a profile of prognostic factors indistinguishable from that of patients with no 13q deletion. This suggests that the overall favourable prognosis associated with 13q deletion is probably attributable to the subset of cases in which both alleles are deleted.