EGFR and lung cancer: Using <i>EGFR</i> mutations (L858R, G719A, Del19) in lung cancer cell lines as a model, IsoPS-DIA achieved subfemtomole sensitivity (LOQ 36-222 amol), excellent linearity across 4 orders of magnitude (<i>R</i><sup>2</sup> = 0.998-0.999), and high reproducibility (median CV ∼ 3%).