Relationship between comorbidity and mortality of stage IV breast cancer: A literature review

Breast cancer is a major health concern on a global scale because breast cancer is the cancer with the highest prevalence and the 5^th highest mortality in women worldwide (The Global Cancer Observatory, 2020). Based on data from the World Health Organization (WHO) in 2020, the prevalence of breast cancer worldwide reached 7,790,717 cases with the 5^th highest mortality rate worldwide. In 2020, breast cancer in Indonesia had the highest prevalence with the 2nd highest mortality rate, namely 22,430 people (The Global Cancer Observatory, 2020). Mortality in breast cancer patients is influenced by various factors, including age, gender, genetics, family history, tumor pathology, clinical parameters (tumor size and location, nodule status, presence of metastatic disease, clinical stage, and histological grade), presence of comorbidities, and type of treatment. Worse survival rates from breast cancer have been found overall in breast cancer patients with comorbidities compared to those without. Literature reviews on breast cancer mortality in patients with and without comorbidities, based on CCI scores, are still very limited. Therefore, researchers are interested in conducting research on the relationship between comorbidities and mortality of breast cancer patients. This review is expected to be useful for enriching knowledge about the relationship between comorbidities and mortality in stage IV breast cancer patients. However, further research is needed with more comprehensive variables to determine the risk factors for breast cancer, the relationship between comorbidities and mortality in breast cancer patients, and survival in breast cancer patients.