Incidence and clinical significance of 6q deletions in B cell chronic lymphocytic leukemia

Deletions affecting the long arm of chromosome 6 (6q) are among the most co mmonly observed chromosomal aberrations in lymphoid malignancies and have b een identified as adverse prognostic factor in subsets of tumors. Whereas a t least two regions of minimal deletion have been established, one in 6q21- q23 and another in 6q25-q27, no tumor suppressor gene that might be involve d in the pathogenesis of lymphoid malignancies has been so far identified f rom these segments. For B cell chronic lymphocytic leukemia (B-CLL) conflic ting data have been reported regarding the incidence and prognostic signifi cance of 6q deletions. tn the current study we have used two YAC clones map ping to deletion regions in bands 6q21 and 6q27 as probes for fluorescence in situ hybridization (FISH) in a large series of B-CLL cases to analyze th e incidence, localization and clinical significance of 6q aberrations. Amon g 285 patients with B-CLL studied we identified 21 cases (7%) with 6q delet ions. All deletions were found with the probe mapping to 6q21 while the 6q2 7 region was deleted only in a third of these cases. Analysis of the clinic al characteristics and laboratory parameters showed that the patients with so deletions had higher white blood cell counts and more extensive lymphade nopathy. However, the overall survival and the treatment-free intervals wer e similar in the two groups. We conclude that deletions in 6q21 occur in 7% of B-CLL and identify a subgroup of patients characterized by a larger tum or mess but no inferior outcome.