Analysis of the chronic lymphocytic leukemia (CLL) coding genome has recently disclosed that the NOTCH1 proto-oncogene is recurrently mutated at CLL presentation. Here, we assessed the prognostic role of NOTCH1 mutations in CLL. Two series of newly diagnosed CLL were used as training (n ؍ 309) and validation (n ؍ 230) cohorts. NOTCH1 mutations occurred in 11.0% and 11.3% CLL of the training and validation series, respectively. In the training series, NOTCH1 mutations led to a 3.77-fold increase in the hazard of death and to shorter overall survival (OS; P < .001). Multivariate analysis selected NOTCH1 mutations as an independent predictor of OS after controlling for confounding clinical and biologic variables. The independent prognostic value of NOTCH1 mutations was externally confirmed in the validation series. The poor prognosis conferred by NOTCH1 mutations was attributable, at least in part, to shorter treatment-free survival and higher risk of Richter transformation. Although NOTCH1 mutated patients were devoid of TP53 disruption in more than 90% cases in both training and validation series, the OS predicted by NOTCH1 mutations was similar to that of TP53 mutated/deleted CLL. NOTCH1 mutations are an independent predictor of CLL OS, tend to be mutually exclusive with TP53 abnormalities, and identify cases with a dismal prognosis. (Blood. 2012;119(2): 521-529)
IntroductionChronic lymphocytic leukemia (CLL) is the most common leukemia in adults. [1][2][3][4] The clinical course of CLL ranges from very indolent, with a nearly normal life expectancy, [5][6][7][8][9] to rapidly progressive leading to death and occasionally undergoing transformation to aggressive lymphoma, known as Richter syndrome (RS). [10][11][12][13][14][15][16][17][18] At presentation, several clinical and biologic features may help to predict, at least in part, the clinical course of CLL. [19][20][21] Of the biologic prognosticators that have been developed, current guidelines for clinical practice recommend screening only for TP53 disruption by mutation, deletion, or both of the locus, that identifies a fraction of high-risk CLL destined to experience a very short survival. 2,[21][22][23][24][25][26][27][28] High-risk CLL, however, cannot be fully recapitulated by TP53 disruption, and other lesions of cancer genes may be implicated in this aggressive phenotype. 29 Recently, two independent investigations of the CLL coding genome have revealed that activating mutations of the NOTCH1 proto-oncogene are recurrently associated with CLL. 30,31 Based on current knowledge, NOTCH1 mutations occur in ϳ 10% CLL at diagnosis and their frequency increases in advanced disease phases, as exemplified by the case of RS. 30,31 The relevance of NOTCH1 mutations in CLL is reinforced by knowledge of activation of the NOTCH1 pathway in this leukemia, 32 and by the possibility of targeting NOTCH1 with drugs currently under development in other clinical contexts. 33 Although not designed to fully assess clinical correlates, the pivotal studies that have ident...
