Insight into del17p low‐frequency subclones in chronic lymphocytic leukaemia (CLL): data from the Australasian Leukaemia and Lymphoma Group (ALLG)/CLL Australian Research Consortium (CLLARC) CLL5 trial

Summary The clinical significance of low‐frequency deletions of 17p13 [tumour protein p53 ( TP53 )] in patients with chronic lymphocytic leukaemia (CLL) is currently unclear. Low‐frequency del17p clones (<25%) were identified in 15/95 patients in the Australasian Leukaemia and Lymphoma Group (ALLG)/CLL Australian Research Consortium (CLLARC) CLL5 trial. Patients with low del17p, without tumour protein p53 ( TP53 ) mutation, had significantly longer progression‐free survival and overall survival durations than patients with high del17p clones. In 11/15 cases with low‐frequency del17p, subclones solely with del17p or del13q were also noted. These data suggest that low‐frequency del17p does not necessarily confer a poor outcome in CLL and challenges the notion of del13q as a founding event in CLL.