The data showed that many of the CTC copy-number profiles were similar to those of the primary and metastatic tumor cells, and that point mutations in APC (encoding adenomatous polyposis coli protein), KRAS, PIK3CA (phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit alpha isoform) and TP53 (cellular tumor antigen p53) in the primary tumors were also present in the single CTCs, suggesting that CTCs will have clinical utility for non-invasive monitoring. This evidence concerns the gene PIK3CA and metastatic neoplasm.