Background According to the Hong Kong Cancer Registry, breast cancer is a leading causes of cancer death in among females in Hong Kong. Local data indicate breast cancer has increased over the years. Previous studies have shown that socioeconomic factors can affect incidence of breast cancer, survival rates and access to treatments. However, there is little literature regarding how socioeconomic status (SES) potentially affects local breast cancer patients. Moreover, there have been no formal studies concerning the economic burden of expensive drugs and treatments among Hong Kong women facing breast cancer. Objectives: The objectives of this study are 1) to investigate the presence of an association between demographical SES and the patient’s usage of targeted therapy, and 2) to briefly discuss how well government drug subsidies can protect patients from catastrophic payments due to expensive trastuzumab. Methods: This dissertation will use a data set from a survey called “The effect of decision aids on treatment decision making for breast cancer surgery: A randomized controlled trial”. The survey targets Cantonese-speaking Chinese females attending one of the forty public hospitals under the Hospital Authority (except for the Queen Elizabeth Hospital). Cross-tabulations and logistic regressions are used to determine the association between SES and patients’ status on using targeted therapy. Results: Bivariate analyses show that associations between SES and those using targeted therapy are only present for certain independent variables including age, education attainment and medical insurance coverage four months and ten months after surgery. The logistic regression indicates that the variables, besides medical insurance coverage, are unable to predict whether the patient chooses targeted therapy or not. Conclusion: To conclude, associations between SES and targeted therapy usage (i.e. either the patient is currently receiving or waiting for therapy) is weak. Even though associations between SES and health outcomes (such as survival and mortality) are well-established, previous studies have commented that the mechanism behind this association is difficult to disentangle. In addition, the association appears weak in this study probably due to the small sample side, complicated interactions between SES and treatment choice, and insufficient information. Second, after comparing the Samaritan Fund and Community Care Fund financial criteria with the monthly household income of females in my data set, it is noticeable that the middle class could be at risk to financial burdens when paying for expensive drugs. / published_or_final_version / Public Health / Master / Master of Public Health