PIK3CA and rectal cancer: The five most frequently altered potentially targetable genes in colon and rectal cancer were PIK3CA (19.6% and 14.2%), PTEN (8.7% and 5.9%), ERBB2 (4.7% and 6.0%), EGFR (2.5% and 2.0%), and FGFR1 (2.0% and 2.7%).