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.