Abstract P2-08-01: Prospective trial of endocrine therapy alone in patients with estrogen receptor positive, HER2-negative, node-negative breast cancer: Results of the TAILORx low risk registry

Background: The Trial Assigning Individualized Options for Treatment (TAILORx) is a prospective trial evaluating the role of endocrine therapy or chemoendocrine therapy in patients 18-75 years of age with estrogen receptor (ER)-positive, HER2-negative breast cancer, a primary tumor between 0.6-5.0 cm, and negative axillary nodes, a population for whom chemotherapy is typically recommended or least considered based on National Comprehensive Cancer Center Network (NCCN) guidelines. Methods: The trial was designed to demonstrate non-inferiority of endocrine therapy compared with chemoendocrine therapy in the randomized group with an Oncotype DX Recurrence Score (RS) of 11-25. Patients with a low RS 25 assigned to chemoendocrine therapy, and both groups were followed in a prospective registry. The definition of an intermediate RS differed in this trial (RS 11-25) from the original reports (RS 18-30) in order to reduce the risk of chemotherapy undertreatment in patients with a mid-range or low RS (Sparano & Paik. J Clin Oncol 2008; 26:721-728). Results: The trial enrolled 10,273 patients between April 2006 and October 2010, of whom 6907 patients (67.2%) had a mid-range RS of 11-25, 1737 (16.9%) had a high RS > 25, and 1639 (15.9%) had a low RS of 60 (39%); tumor size 2 cm (31%); histologic grade low (34%), intermediate (59%), high (7%); breast conservation (68%) or mastectomy (32%). Initial endocrine therapy included tamoxifen in 35%, aromatase inhibitors in 59%, ovarian function suppression in 3%, and unspecified therapy in 3%; 5 patients received adjuvant chemotherapy (1 of whom relapsed). Five-year rates (and 95% confidence intervals [CI]) for low RS group were 99.2% (98.5, 99.6%) for distant relapse free interval, 98.5% (97.7, 99.1%) for relapse-free interval, 93.7% (92.2, 94.9%) for invasive disease free survival, and 98.2% (97.3, 98.7%) for overall survival. Information regarding ER, PR, and HER2 RNA expression will be presented. Conclusions: Despite meeting guidelines for recommending or at least considering adjuvant chemotherapy based on classical clinicopathologic features, the risk of recurrence was very low at 5 years in patients with ER-positive, HER2-negative, axillary node-negative breast cancer and a low RS of Citation Format: Sparano JA, Gray RJ, Makower DF, Pritchard KI, Albain KS, Hayes DF, Geyer Jr CE, Dees EC, Perez EA, Olson Jr JA, Zujweski J, Keane MM, Gomez Moreno HL, Reddi RP, Goggins TF, Mayer IA, Brufsky AM, Toppmeyer DL, Kaklamani VG, Atkins JN, Berenberg JL, Sledge Jr GW. Prospective trial of endocrine therapy alone in patients with estrogen receptor positive, HER2-negative, node-negative breast cancer: Results of the TAILORx low risk registry. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-08-01.