Genomic and Molecular Prognostic Factors

Number of non–RAS pathway variants. A predictor of prognosis for children with JMML is the number of variants beyond the disease-defining RAS pathway variants.[405,406]

Number of non–RAS pathway variants. A predictor of prognosis for children with JMML is the number of variants beyond the disease-defining RAS pathway variants.[405,406]

One study observed that zero or one somatic alteration (pathogenic variant or monosomy 7) was identified in 64 patients (65.3%) at diagnosis, whereas two or more alterations were identified in 34 patients (34.7%).[406] In multivariate analysis, variant number (2 or more vs. 0 or 1) maintained significance as a predictor of inferior event-free survival (EFS) and overall survival (OS). A higher proportion of patients diagnosed with two or more alterations were older and male, and these patients also demonstrated a higher rate of monosomy 7 or somatic NF1 variants.[406]

Number of non–RAS pathway variants. A predictor of prognosis for children with JMML is the number of variants beyond the disease-defining RAS pathway variants.[405,406]

Another study observed that approximately 60% of patients had one or more additional variants beyond their disease-defining RAS pathway variant. These patients had an inferior OS compared with patients who had no additional variants (3-year OS rate, 61% vs. 85%, respectively).[405]

Number of non–RAS pathway variants. A predictor of prognosis for children with JMML is the number of variants beyond the disease-defining RAS pathway variants.[405,406]

A third study observed a trend for an inferior OS for patients with two or more variants compared with patients with zero or one variant.[407]

RAS pathway double variants. Although variants in the five canonical RAS pathway genes associated with JMML (NF1, NRAS, KRAS, PTPN11, and CBL) are generally mutually exclusive, 4% to 17% of cases have variants in two of these RAS pathway genes.[405,406] This finding has been associated with a poorer prognosis.[405,406]

RAS pathway double variants. Although variants in the five canonical RAS pathway genes associated with JMML (NF1, NRAS, KRAS, PTPN11, and CBL) are generally mutually exclusive, 4% to 17% of cases have variants in two of these RAS pathway genes.[405,406] This finding has been associated with a poorer prognosis.[405,406]

Two RAS pathway variants were identified in 11% of JMML patients in one report, and these patients had a significantly inferior EFS rate (14%) compared with patients who had a single RAS pathway variant (62%). Patients with Noonan syndrome were excluded from the analyses.[406]

RAS pathway double variants. Although variants in the five canonical RAS pathway genes associated with JMML (NF1, NRAS, KRAS, PTPN11, and CBL) are generally mutually exclusive, 4% to 17% of cases have variants in two of these RAS pathway genes.[405,406] This finding has been associated with a poorer prognosis.[405,406]

Similar findings for RAS pathway variants were reported in a second study. This study observed that patients with RAS pathway double variants (15 of 96 patients) had lower survival rates than did patients with either no additional variants or with additional variants beyond the RAS pathway variant.[405]

DNA methylation profile.

DNA methylation profile.

One study applied DNA methylation profiling to a discovery cohort of 39 patients with JMML and to a validation cohort of 40 patients. Distinctive subsets of JMML with either high, intermediate, or low methylation levels were observed in both cohorts. Patients with the lowest methylation levels had the highest survival rates, and all but 1 of 15 patients experienced spontaneous resolution in the low methylation cohort. High methylation status was associated with lower EFS rates.[409]

DNA methylation profile.

Another study applied DNA methylation profiling to a cohort of 106 patients with JMML. The study observed one subgroup of patients with a hypermethylation profile and one subgroup of patients with a hypomethylation profile. Patients in the hypermethylation group had a significantly lower OS rate than did patients in the hypomethylation group (5-year OS rate, 46% vs. 73%, respectively). Patients in the hypermethylation group also had a significantly poorer 5-year transplant-free survival rate than did patients in the hypomethylation group (2.2%; 95% CI, 0.2%–10.1% vs. 41.2%; 95% CI, 27.1%–54.8%). Hypermethylation status was associated with two or more variants, higher fetal hemoglobin levels, older age, and lower platelet count at diagnosis. All patients with Noonan syndrome were in the hypomethylation group.[407]

DNA methylation profile.

A study examined 33 patients with JMML who had CBL variants. The study identified 31 patients with low methylation and 2 patients with intermediate methylation. Both of the children with intermediate methylation relapsed after undergoing HSCT. Because treatment, which included observation only, varied among the 31 patients with low methylation, the impact of the methylation profile on therapeutic decisions and outcomes could not be fully assessed. However, the methylation status was not prognostic of spontaneous resolution.[410]

LIN28B overexpression. LIN28B overexpression, which is present in approximately one-half of children with JMML, identifies a biologically distinctive subset of JMML. LIN28B is an RNA-binding protein that regulates stem cell renewal.[411]

LIN28B overexpression. LIN28B overexpression, which is present in approximately one-half of children with JMML, identifies a biologically distinctive subset of JMML. LIN28B is an RNA-binding protein that regulates stem cell renewal.[411]

LIN28B overexpression was positively correlated with high blood fetal hemoglobin level and age (both of which are associated with poor prognosis), and it was negatively correlated with presence of monosomy 7 (also associated with inferior prognosis). Although LIN28B overexpression identifies a subset of patients with increased risk of treatment failure, it was not found to be an independent prognostic factor when other factors such as age and monosomy 7 status are considered.[411]

LIN28B overexpression. LIN28B overexpression, which is present in approximately one-half of children with JMML, identifies a biologically distinctive subset of JMML. LIN28B is an RNA-binding protein that regulates stem cell renewal.[411]

Another study also observed a subset of JMML patients with elevated LIN28B expression. The study identified LIN28B as the gene for which expression was most strongly associated with hypermethylation status.[407]