Risk of early progression according to circulating ESR1 mutation, CA-15.3 and cfDNA increases under first-line anti-aromatase treatment in metastatic breast cancer

摘要

Endocrine therapy is recommended as a first-line treatment for hormone receptor-positive metastatic breast cancer (HR MBC) patients. No biomarker has been validated to predict tumor progression in that setting. We aimed to prospectively compare the risk of early progression according to circulating ESR1 mutations, CA-15.3, and circulating cell-free DNA in MBC patients treated with a first-line aromatase inhibitor (AI). Patients with MBC treated with a first-line AI were prospectively included. Circulating biomarker assessment was performed every 3?months. The primary objective was to determine the risk of progression or death at the next follow-up visit (after 3?months) in case of circulating ESR1 mutation detection among patients treated with a first-line AI for HR MBC. Overall, 103 patients were included, and 70 (68%) had progressive disease (PD). Circulating ESR1 mutations were detected in 22/70 patients with PD and in 0/33 patients without progression (p??0.001). Among the ESR1-mutated patients, 18/22 had a detectable mutation prior to progression, with a median delay of 110?days from first detection to PD. The detection of circulating ESR1 mutations was associated with a 4.9-fold (95% CI 3.0–8.0) increase in the risk of PD at 3?months. Using a threshold value of 25% or 100%, a CA-15.3 increase was also correlated with progression (p??0.001 and p?=?0.003, respectively). In contrast to ESR1, the CA-15.3 increase occurred concomitantly with PD in most cases, in 27/47 (57%) with a 25% threshold and in 21/25 (84%) with a 100% threshold. Using a threshold value of either 25% or 100%, cfDNA increase was not correlated with progression. The emergence of circulating ESR1 mutations is associated with a 4.9-fold increase in the risk of early PD during AI treatment in HR MBC. Our results also highlighted that tracking circulating ESR1 mutations is more relevant than tracking CA-15.3 or cfDNA increase to predict progression in this setting. ClinicalTrials.gov, NCT02473120. Registered 16 June 2015—retrospectively registered after one inclusion (first inclusion 1 June 2015).