# Clinical, Sociodemographic, and Facility-Related Factors Influencing HER2-Targeted Therapy in Metastatic Hormone Receptor-Negative, HER2-Positive Breast Cancer

## TL;DR

This study finds that access to HER2-targeted therapy for a specific type of breast cancer varies by age, insurance, and treatment location, and that receiving this therapy significantly improves survival.

## Contribution

The study identifies disparities in HER2-targeted therapy access and survival outcomes across sociodemographic and facility-related factors in metastatic breast cancer patients.

## Key findings

- HER2-targeted therapy use increased over time but disparities persist based on age, race, insurance, and facility type.
- Patients receiving HER2-targeted therapy had significantly better survival (median 5.08 vs. 1.27 years).
- Private insurance and academic treatment centers were associated with higher therapy use.

## Abstract

Patients with metastatic HER2-positive breast cancer that is not sensitive to hormone therapy often face a rapidly progressing illness with limited options. Although the introduction of HER2-targeted therapies has led to significant improvements in survival, access to these treatments is not consistent across all patient populations. In this retrospective study of over 3000 patients using a national cancer database, we examined how factors such as age, race, insurance status, treatment facility type, and year of diagnosis influence the likelihood of receiving HER2-targeted therapy. We found that while the use of these therapies has increased over time, notable disparities remain. Younger patients, those with private insurance, and those treated at academic centers were more likely to receive targeted treatments. Importantly, patients who received HER2-targeted therapy had significantly better survival. These results underscore the importance of addressing access barriers to ensure all patients can benefit from these life-prolonging therapies.

Background/Objectives: The use of HER2-targeted therapies has significantly improved survival outcomes in metastatic hormone receptor-negative, HER2-positive (HR−/HER2+) breast cancer. However, factors influencing their adoption remain unclear. This study examines clinical, sociodemographic, and facility-related determinants of HER2-targeted therapy utilization in metastatic HR−/HER2+ breast cancer. Methods: We conducted a retrospective cohort study of metastatic HR−/HER2+ breast cancer patients from the NCDB (2013–2020), categorizing them into HER2-targeted therapy recipients and non-recipients. Patients with missing key variables were excluded. Time periods were divided as pre-2015, 2016–2018, and 2019–2020 to reflect evolving treatment availability and uptake in the United States. Univariable and multivariable logistic regression identified factors associated with HER2-targeted therapy use. Cox proportional hazards regression and log-rank tests assessed overall survival. Results: Among 3060 metastatic HR−/HER2+ breast cancer patients, 2318 (75.8%) received HER2-targeted therapy. HER2-targeted therapy utilization increased from 64.6% in 2013 to 80.9% in 2016, marking an early period of rapid uptake. Usage remained consistently high from 2016 to 2018, followed by a slight decline and stabilization around 75% from 2019 to 2020. Factors positively associated with therapy use included diagnosis in 2016–2018 (OR 1.93, p < 0.001) and 2019–2020 (1.88, p < 0.001), private insurance (OR 1.76, p < 0.001), and treatment at academic facilities (OR 1.39, p = 0.031). Reduced likelihood of therapy use was observed in patients aged 71+ (OR 0.52, p < 0.001), Black race (OR 0.78, p = 0.018), Medicare insurance (OR 0.64, p < 0.001), and treatment at rural facilities (OR 0.59, p = 0.022). HER2-targeted therapy was associated with significantly improved survival (median 5.08 vs. 1.27 years, log-rank p < 0.001) and lower mortality risk (HR 0.52, p < 0.001). Conclusions: The adoption of HER2-targeted therapy has increased in recent years, yet disparities persist in access and utilization. Our findings highlight the need to address sociodemographic and facility-related barriers to ensure equitable treatment and improved survival outcomes for all patients.