Acknowledgements: We thank all patients who contributed to this study. The work was supported by grants from the Instituto de Salud Carlos III (ISCIII, MINECO) (operating grants: PI13/00285 and RD12/0036/0008 awarded to C.L. and PIE13/00022 and RD12/0036/0031 awarded to G.C.) and confunded by FEDER funds/European Regional Development Fund (ERDF) - a way to Build Europe-"// FONDOS FEDER "una manera de hacer Europa", the Generalitat de Catalunya (Government of Catalonia) (operating grant 2014SGR338, awarded to G.C.) and the Asociación Española Contra el Cáncer (operating grants, 2010 Grupos Estables, awarded to G.C.). J.B. received a Spanish Society of Medical Oncology grant. This activity is sponsored by the ISCIII Ministerio de Economía y Competitividad (PT13/0001/0044).

Next generation sequencing panels have been developed for hereditary cancer, although there is some debate about their cost-effectiveness compared to exome sequencing. The performance of two panels is compared to exome sequencing. Twenty-four patients were selected: ten with identified mutations (control set) and fourteen suspicious of hereditary cancer but with no mutation (discovery set). TruSight Cancer (94 genes) and a custom panel (122 genes) were assessed alongside exome sequencing. Eightythree genes were targeted by the two panels and exome sequencing. More than 99% of bases had a read depth of over 30x in the panels, whereas exome sequencing covered 94%. Variant calling with standard settings identified the 10 mutations in the control set, with the exception of MSH6 c.255dupC using TruSight Cancer. In the discovery set, 240 unique non-silent coding and canonic splice-site variants were identified in the panel genes, 7 of them putatively pathogenic (in ATM, BARD1, CHEK2, ERCC3, FANCL, FANCM, MSH2). The three approaches identified a similar number of variants in the shared genes. Exomes were more expensive than panels but provided additional data. In terms of cost and depth, panels are a suitable option for genetic diagnostics, although exomes also identify variants in non-targeted genes.