Treatment sequences and survival outcomes in advanced HR + HER2- breast cancer patients: a real-world cohort.

Purpose: Palliative treatment options for HR + HER2- advanced breast cancer (ABC) patients have increased, but data is lacking about the optimal treatment sequence. We used real-world data from a comprehensive cancer center to describe applied treatment sequences and we determined treatment-related and survival outcomes.

Methods: Patients aged 18 years and older with HR + HER2- ABC treated with systemic treatment were included in this historic cohort study. Sequential treatment schedules, time to treatment discontinuation, time to chemotherapy, and overall survival (OS) were determined, stratified by first-line treatment.

Results: 202 patients were included. They received a total of 650 treatment lines (median 3; range: 1-11). 91 (45%), 25 (12%), 24 (12%), 28 (14%), 22 (11%) and 12 (6%) patients started first-line treatment with non-steroidal aromatase inhibitors (NSAI), NSAI + cyclin dependent kinase 4/6-inhibitors (CDK4/6i), fulvestrant + CDK4/6i, tamoxifen, chemotherapy and other treatment, respectively. 10, 13, and 14 different treatment regimens were given in first, second and third-line, respectively. Of the patients who started first-line NSAI monotherapy (n = 91), 3 (3%) died before receiving second-line treatment.

Conclusion: In this real-world cohort, we observed a wide variety of different treatment sequences applied in daily clinical practice, some of which were in discordance with the current guidelines. Fear that patients may never get around to treatment with CDK4/6i if a patient did not start with a CDK4/6i was not supported by our study results.