Beyond the median: Estimating survival times for patients starting endocrine therapy for estrogen receptor-positive, metastatic breast cancer from recent randomized trials

Aim: To estimate scenarios for survival for patients with estrogen receptor (ER) positive, metastatic breast cancer (MBC) and to help communicate prognosis to patients starting endocrine therapy (ET). Methods: We searched for randomized trials of ET for ER-positive MBC and extracted the following percentiles (representative survival scenarios) from each overall survival (OS) curve: 90th (worst-case), 75th (lower-typical), 50th (median), 25th (upper-typical), and 10th (best-case). We then assessed the accuracy of estimating these percentiles for each OS curve by multiplying the median OS by four simple multiples: 0.25 (to estimate the 90th percentile), 0.5 (75th), 2 (25th), and 3 (10th). Estimates were deemed accurate if it fell within 0.75–1.33 times the actual value. Results: We identified 25 trials with 10,566 patients. The median OS (interquartile range) was: 61.3 months (53.4–64.8) for first-line ET with cyclin-dependant kinase 4/6 inhibitors (four treatment groups); 42.6 months (40.9–50.4) for first-line ET alone (21 treatment groups) and 29.2 months (24.8–33.4) for subsequent line ET (19 treatment groups). Simple multiples of the median OS accurately estimated the 90th percentile in 80%; 75th percentile in 93%; and 25th percentile in 76% of curves. The 10th percentile was only available for four OS curves and could not be evaluated. Conclusion: Simple multiples of the median OS are a helpful and accurate method to assist in estimating and discussing scenarios for survival for MBC patients starting ET. Longer follow-up of trials is required to help clinicians estimate the best-case scenario.