Lines Left Uncrossed: The Cost of Attrition in Metastatic Triple Negative Breast Cancer

Background Treatment attrition poses an important challenge in the management of breast cancer patients worldwide. There is a paucity of data specifically addressing the attrition rates of metastatic triple-negative breast cancer (mTNBC), which has the worst survival among all breast cancer subtypes. Materials and methods In this retrospective study, we assessed attrition rates among patients with metastatic TNBC and their causative factors. Additionally, we analyzed the median progression-free survival (PFS) across each line of therapy (LOT) and the median overall survival (OS). Attrition was defined as discontinuation of anti-cancer therapy due to any cause. The case records of all patients with metastatic TNBC treated between January 01, 2017, and December 31, 2021, were screened, and relevant data were extracted in a pre-specified format. Results Seventy patients with metastatic TNBC were included for analysis. The median age was 50 years (range: 29-82). About 18 patients (25.7%) experienced attrition before initiating any anticancer therapy for metastatic TNBC. Following each LOT, attrition occurred as follows: 28.5% after the first line, 14.2% after the second line, 5.7% after the third line, and 4.2% after the fourth line. Only two patients received fifth-line therapy; both had attrition. The leading causes for attrition were decline of performance status, followed by disease progression. Median PFS declined with each LOT, and median OS was 14.8 months. Conclusions In our study, all patients with metastatic TNBC experienced treatment attrition, with the majority receiving two or fewer LOT. Declining performance status and disease progression were the leading causes for attrition. The median PFS reduced with successive treatment lines, underscoring the need for earlier, more effective treatments.