Previous reports have demonstrated that genotoxic chemotherapy increases the selective pressure on malignant clones to lose key tumor suppressor genes through LOH.5, 12, 19 In CLL, patients with underlying loss or mutation of one TP53 allele may selectively undergo a clonal selection for loss of the remaining wild-type allele following the use of chemoimmunotherapy, leading to reduced survival. This evidence concerns the gene TP53 and B-cell chronic lymphocytic leukemia.