ERBB2 and breast cancer: In Vietnam, the option of using trastuzumab in combination with chemotherapy for early breast cancer patients with HER2+ is not cost-effective compared to chemotherapy alone, with an ICER value of 519,616,972 VND (US$ 22,845) per QALY gained, which is six times higher than the current threshold of 1-time GDP per capita (i.e., US$ 3,600).