Recurrence rate in patients with stage IV breast cancer: a retrospective cohort study

Abstract Introduction: Metastatic breast cancer (mBC) remains incurable, with a median overall survival (OS) of approximately 3 years and a 5-year survival rate of approximately 25%, irrespective of the economic classification of the country where treatment is received. Cyclin-dependent kinase (CDK) inhibitors increase overall survival in both first and second-line settings in the treatment of hormone receptor–positive, human epidermal growth factor receptor 2–negative mBC. This retrospective cohort study investigated the progression-free survival in women with mBC receiving combination therapy with abemaciclib (CDK4/CDK6 inhibitor) and letrozole or fulvestrant as opposed to abemaciclib only. Methods: The study included all eligible women with stage IV breast cancer treated with abemaciclib at a private oncology facility in Johannesburg over the study period. Data were collected from medical records from April 1, 2019 to March 31, 2021. Analyses were conducted to assess the overall survival rate, progression-free survival probability, and safety of abemaciclib in women with stage IV breast cancer. Results: Thirty-two patients were eligible for inclusion in this study. The progression-free survival probability was 60% after a period of 17 months, irrespective of treatment options. After 17 months, the OS of women on a combination of abemaciclib and letrozole was 80%, on a combination of abemaciclib and fulvestrant was 80%, and on abemaciclib monotherapy was 70%. The most noted adverse effects were diarrhea (92.0%), neutropenia (92.0%), fatigue (48.0%), and hepatotoxicity (16.0%). Discussion: Abemaciclib with endocrine therapy or an aromatase inhibitor provided an improvement in the OS compared with abemaciclib monotherapy. These findings are representative of the use of abemaciclib in a local population and are similar to those of larger studies conducted internationally.