OBJECTIVES: To evaluate the direct medical cost of HER2+ early breast cancer patients who developed metastasis, the 5-year relapse rate despite trastuzumab-based treatment, and the potential cost impact of introducing pertuzumab in HER2+ early breast cancer treatment in Hong Kong.

METHODS: It was a population-based observational study using Clinical Data Analysis and Reporting System. All patients who received trastuzumab in Hong Kong public hospitals between 2014 and 2019 were screened. Patients’ medication, hospitalization, and procedural history were retrieved. Costs were calculated based on the gazette and analyzed from healthcare payer perspective.

RESULTS: A total of 4136 patients were diagnosed with HER2+ breast cancer and treated with trastuzumab between 2014 and 2019. Among them, 780 had metastasis. Their mean direct medical cost was USD 65,096.3 per year, including medication cost of USD 34,306.4, hospitalization cost of USD 25,003.7, and procedural cost of USD 5,786.2. There were 678 patients diagnosed with HER2+ breast cancer in 2014 and 605 received trastuzumab-based treatment before metastasis. Out of the 605 patients, 106 had metastasis and 11 had local recurrence within 5 years. The 5-year metastasis rate was 17.52% and 5-year recurrence rate was 19.34%. Out of the 678 patients, 19 received pertuzumab before metastasis, 33 received pertuzumab after metastasis, 652 did not receive pertuzumab before metastasis (either received pertuzumab after metastasis or had never received pertuzumab). Compared with using pertuzumab after metastasis, using pertuzumab before metastasis yielded an ICER of USD -92,263.1, which appeared cost-saving. Compared with not using pertuzumab before metastasis, using pertuzumab before metastasis yielded an ICER of USD 319,773.2.

CONCLUSIONS: Adding pertuzumab to HER2+ early breast cancer treatment might be cost-effective in patients at high risk of metastasis. Future studies could target patients with additional risks of recurrence or metastases.