In the model’s results, patients with the breast cancer subtype with the worst prognosis (ER−/PR−) receive twice the health benefit (in quality-adjusted life-years, a measure of disease burden that considers the quality and quantity of life lived) of those with the subtype with the best prognosis (ER+/PR+) for trastuzumab therapy versus chemotherapy alone. This evidence concerns the gene PGR and breast carcinoma.