Nevertheless, even though the sensitivity decreased for the serum assay, the electrochemical immunosensor is still suitable to detect HER-1 biomarkers in breast cancer patients, as it covered the full critical clinical concentration range (i.e., 1.0–25 ng mL−1 in healthy people and 11–30 ngmL−1 in patients with primary and metastatic cancer). This evidence concerns the gene EGFR and breast cancer.