Among patients receiving HER2-targeted agents, HT+ patients had adjusted PPPM all-cause costs of $10,359 and breast cancer-specific costs of $6,869, which were $2,565 lower (95% CI: −$3,397 to −$1,733) and $888 lower (95% CI: −$1,472 to −$305), respectively, than the HT− patients. The gene discussed is ERBB2; the disease is breast carcinoma.