Real-WorldClinical Outcomes in Biological Subgroups of Breast Cancer in the Hospital District of Southwest Finland

Abstract

Background Comparing breast cancer survival trends globally, Finland is among the top three countries in Europe. However, outcome data on breast cancer subgroups in the Finnish population is limited. This retrospective registry‐based study aimed to assess patient characteristics and clinical outcomes of different breast cancer subgroups in early (EBC) and metastatic breast cancer (MBC) in a real‐life clinical setting. Patients and Methods The study consisted of 6977 adult female breast cancer patients diagnosed in Southwest Finland during 2005‐2018. Patients were divided into four mutually exclusive groups: human epidermal growth factor receptor 2 positive (HER2+), triple negative, HER2‐/hormone receptor positive (HR+), and HER2 and/or HR status unknown, and further into EBC and MBC patients. Real‐world (rw) clinical outcomes: disease free survival (rwDFS), progression free survival (rwPFS), overall survival (OS) and distant recurrence‐free interval (rwDRFI) were assessed. Results Within EBC 5‐year survival was the highest 88% in HER2‐/HR+, 85% in HER2+, and 75% in triple negative. The rwDFS varied significantly in EBC (5‐year rwDFS HER2+, triple negative, HER2‐/HR+: 80%, 71%, 87% respectively). In MBC median survival was 2 years for both HER2‐/HR+ and HER2+, and markedly shorter for triple negative (0.8 years). Independent predictors of mortality were age (HR 1.1), other subgroups than HER2‐/HR+ (HR 1.2‐1.9), metastatic disease (HR 9.8), and other malignancies (HR 2.7). Conclusions This registry‐based study demonstrates significant differences in breast cancer outcomes on the subgroup level, as well as poorer outcomes compared to clinical trials, giving complementary insight on clinical characteristics in an unselected patient population. Implications for practise This retrospective registry‐based study assessed the clinical outcomes of different breast cancer subgroups in 6977 adult female breast cancer patients diagnosed in Southwest Finland during 2005‐2018. Results demonstrated significant variation in the survival between subgroups in both EBC and MBC, as well as differences between unselected patients representing the standard of care and randomized clinical trials. Although, according to the global comparison of survival trends, the net survival of breast cancer patients in Finland is generally high, there is great variation between subgroups. This real‐life breast cancer data provides tools to further evaluate medical need in different breast cancer subgroups.