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Open Access Highly Accessed Research article

Comparing somatic mutation-callers: beyond Venn diagrams

Su Yeon Kim1 and Terence P Speed12

Author Affiliations

1 Department of Statistics, University of California at Berkeley, 367 Evans Hall, Berkeley, CA 94720 USA

2 Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia

BMC Bioinformatics 2013, 14:189  doi:10.1186/1471-2105-14-189

Published: 10 June 2013

Abstract

Background

Somatic mutation-calling based on DNA from matched tumor-normal patient samples is one of the key tasks carried by many cancer genome projects. One such large-scale project is The Cancer Genome Atlas (TCGA), which is now routinely compiling catalogs of somatic mutations from hundreds of paired tumor-normal DNA exome-sequence data. Nonetheless, mutation calling is still very challenging. TCGA benchmark studies revealed that even relatively recent mutation callers from major centers showed substantial discrepancies. Evaluation of the mutation callers or understanding the sources of discrepancies is not straightforward, since for most tumor studies, validation data based on independent whole-exome DNA sequencing is not available, only partial validation data for a selected (ascertained) subset of sites.

Results

To provide guidelines to comparing outputs from multiple callers, we have analyzed two sets of mutation-calling data from the TCGA benchmark studies and their partial validation data. Various aspects of the mutation-calling outputs were explored to characterize the discrepancies in detail. To assess the performances of multiple callers, we introduce four approaches utilizing the external sequence data to varying degrees, ranging from having independent DNA-seq pairs, RNA-seq for tumor samples only, the original exome-seq pairs only, or none of those.

Conclusions

Our analyses provide guidelines to visualizing and understanding the discrepancies among the outputs from multiple callers. Furthermore, applying the four evaluation approaches to the whole exome data, we illustrate the challenges and highlight the various circumstances that require extra caution in assessing the performances of multiple callers.

Keywords:
Cancer genome; Next-generation sequencing; Somatic mutation-calling; Methods comparison; Validation