Metastatic Colorectal Adenocarcinoma Tumor Purity Assessment from Whole Exome Sequencing Data

As molecular medicine wields greater and greater influence on cancer patient care, including therapeutic selection, it becomes increasingly important to understand the power and deficiencies of computational tools used in decision making processes. Here we use a set of unselected metastatic colorectal tumor samples in a head-to-head comparison between the calculation of stromal content by a board certified pathologist, versus that derived from whole exome sequencing and purity assessment by a variety of common computational methods. We find that in about 1/2 of the samples the computational methods each do a poor job of assessing the percent stromal contamination, and as a result, tumor variant allele frequencies (VAFs) are low or undetected, whereas analysis of organoids derived from the same tumors yielded much higher VAFs in keeping with their lower stromal content. The whole exome sequence of our samples is available via dbGaP, accession phs003059.v1.p1.]]>
Inclusion: Snap frozen sample available from resected and histologically diagnosed colorectal adenocarcinoma liver metastasis Known history of chemotherapeutic treatment prior to hepatectomy Exclusion: Concurrent history of another primary cancer ]]>
Study specimens were collected during hepatectomy operations, snap frozen in liquid nitrogen and archived at -80C before rapid defrosting and processing for RNA-free genomic DNA isolation.]]>