Abstract P3-06-14: Serum activin A and response to the aromatase inhibibitor (AI) letrozole versus tamoxifen in metastatic breast cancer

Introduction : The prognostic and predictive utility of pretreatment serum activin A (TGF-B superfamily ligand) was correlated with the response of first-line metastatic breast cancer patients (MBC) in the phase 3 randomized trial of letrozole vs. tamoxifen. Methods: 555 ER + first-line MBC patients had pretreatment serum available for activin A ELISA (RD p In the total population with available serum (n=555), multivariate analysis for TTP revealed that high serum activin A was a significant adverse prognostic factor (HR=1.46, p Conclusions: Patients with high pretreatment serum activin A levels had a significantly reduced ORR, CBR, TTP and OS compared to patients with low serum activin A. The results were similar within the letrozole or tamoxifen treatment arms, and within the serum HER2 not-elevated subgroups. High pretreatment serum activin A level is associated with relative resistance to hormone therapy in first-line metastatic breast cancer. Citation Format: Meghan Jensen, Ashley Kang, Suhail M Ali, Kim Leitzel, Ashwani Garg, Jaqueline Rogerio, David Chen, Raymond Hall, Scott Hofsess, Hilary A Chaudri-Ross, Nicholas Bade, Walter P Carney, Allan Lipton. Serum activin A and response to the aromatase inhibibitor (AI) letrozole versus tamoxifen in metastatic breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P3-06-14.