M3P sequencing panel identifies TP53 mutational status as a prognostic factor in chemotherapy-naive multiple myeloma

Embedded Image Introduction Multiple myeloma (MM) is characterized by a highly variable disease course, which can be traced to initiating and acquired genomic events. Whole exome analysis of matched tumor and germline DNA from 287 MM patients identified recurrently somatically mutated genes (RSMGs) (Lohr et al. - Cancer Cell 2014, Bolli et al. - Nat Commun 2014). Despite the fact that these RSMGs affect pathways that are biologically important in MM, the clinical relevance of many of these genes in the context of conventional prognostic markers remains to be elucidated. Aims The aims of this pilot study were: (1) To validate the prevalence of RSMGs in our newly diagnosed MM patient cohort; (2) To assess the correlation between RSMGs, clinical parameters and outcome; (3) To thereby identify the potential clinical usefulness of introducing RSMG mutational profiling in larger MM trial cohorts. Material and Methods CD138+ enriched MM cells and peripheral blood were obtained with informed consent from chemotherapy-naive patients, participating in 3 clinical trials: HOVON-65/GMMG-HD4, HOVON-87/NMSG-18 and Carthadex (EudraCT number 2004-000944-26, 2007-004007-34 and 2009-014922-40, respectively). Matched tumor and germline DNA were sequenced on an Ion Torrent sequencing platform (PGM, Life Technologies), using the M3 P Mutational Panel v3.0, comprising 1327 customized oligos (Life Technologies), targeted at the coding sequences of 88 MM-relevant genes, including the RSMGs. Somatic mutations were considered positive when present in >=10% of tumor reads and 1 year (n=23 versus n=79), only showed a significant correlation with TP53 mutational status (adj. p-value=0,012). TP53 mutational status remained the only significant prognostic factor when comparing patients with an OS 1 year (adj. p-value=0,003; n=13 versus n=89). When comparing the number of mutated genes, del17p and t(4;14) status, EMC92 score, transplant versus non-transplant protocol and ISS stage between TP53 mutated and wildtype MM, TP53 mutated patients had a significantly higher number of mutated genes in the M3 P panel (adj. p-value=0,001). Conclusions (1) With the M3 P Mutational Panel, we confirm the published prevalence of RSMGs in MM in our cohort of chemotherapy-naive patients. NRAS, KRAS, DIS3, FAM46C, TP53 and BRAF are the most frequently mutated genes. (2) TP53 mutational status is the strongest unfavorable prognostic factor in our cohort and it seems to be associated with greater mutational burden. Validation in a more extensive population is planned. (3) This warrants further investigation of the mutational status of these genes in larger clinical trial cohorts, enabling a more robust comparison with conventional prognostic markers in a multivariate analysis.