Mandatory tumor and serum samples were collected ( N = @ ; @ % to @ % were assessable ) , and amphiregulin , betacellulin , epidermal growth factor ( EGF ) , transforming growth factor alpha , EGF receptor , HER@ , HER@ , insulin-like growth factor @ receptor , PTEN , phosphorylated AKT , PIK@CA , CMYC , serum HER@ extracellular domain ( sHER@ ) , and FCR were assessed using appropriate assays .