Does guideline non-adherence result in worse clinical outcomes for hormone receptor-positive and HER2-negative metastatic breast cancer in premenopausal women?: result of an institution database from South Korea

摘要

BackgroundBreast cancer is the most common cancer in women worldwide and the leading cause of cancer death in women [1, 2]. Hormone receptor positive (HR-positive) subtype represents the majority of the patients with breast cancer (60–75%) [3], and early stage HR-positive patients receive adjuvant endocrine therapy after curative aim of treatment. Nevertheless, about 30% of early HR-positive breast cancer develops into metastatic disease over time, and de novo metastatic breast cancer represents about 5–10% of all breast cancer [4]. Despite the advancement in breast cancer management, metastatic breast cancer (MBC) continues to portend poor prognosis with 5-year survival rate of just 25% [2].Endocrine therapy is the preferred option for the treatment of HR-positive, HER2-negative MBC, exclusive of visceral crisis or endocrine resistance [5]. So far, the consensus has been that initial palliative chemotherapy appears to be inferior to endocrine therapy in terms of efficacy and toxicity [6]. However, real-world practicing patterns differ from the guidelines with a considerable portion of patients with HR-positive/HER2-negative MBC still receiving initial palliative chemotherapy rather than endocrine therapy, with non-adherent practice resulting in worse outcomes [7].In Asian populations, patients with breast cancer have distinct demographic characteristics compared to Western counterparts [8, 9]. The peak incidence for breast cancer is in the 40s among Asian patients, in contrast to the 60s in the United States [8]. The premenopausal patients make up about half of the whole breast cancer population in Asian countries, with approximately 10% of the patients being younger than 35?years [10, 11]. This must be understood in the context that breast cancer is known to be more aggressive and associated with poorer prognosis for premenopausal patients [12]. In this study, we observe the patterns of initial palliative treatment for premenopausal patients with HR-positive/HER2-negative MBC and determine if nonadherence to clinical guidelines are associated with worse clinical outcomes in terms of PFS and OS in the South Korean population.