The no treatment cohort incurred higher expenditures for all-cause ($6,683 no treatment, $3,416 no HER2-targeted agents, and $3,327 HER2-targeted agents; P < 0.001) and breast cancer-related inpatient admissions ($1,525 no treatment, $271 no HER2-targeted agents, and $338 HER2-targeted agents; P < 0.001) than those in the other cohorts. The gene discussed is ERBB2; the disease is breast carcinoma.