Abstract P3-07-63: Ki67 cut-off point to predict the benefit of adjuvant chemotherapy in ER+ HER2- breast cancer patients

BACKGROUND: The benefit of chemotherapy for patients with estrogen receptor(ER)+ HER2- breast cancers is an ongoing question. The evaluation of the tumor9s proliferation by Ki67 may guide the indication but no consensual predictive cut-off has been set yet. MATERIALS AND METHODS: This study included women with a first ER+HER2- invasive breast cancer treated by primary surgery between 2003 and 2008. Data was collected prospectively. Ki67 cut-off was sequentially set each 1% from 5% to 30%. For each threshold, the interaction between Ki67 and adjuvant chemotherapy was integrated in a multivariate Cox model to determine when it became statistically significant in predicting distant-disease free survival (DDFS). Using different Ki67 cut-offs, we also compared DDFS of patients who had or not an indication of chemotherapy, depending on whether they actually received it or not. RESULTS: Among the 3221 breast cancers, median Ki67 was 10%, with a mean of 15% (S.D = 14). Ki67 was an independent prognosis factor whether the cut-off was set to 14% or to 20% (p CONCLUSION: In ER+ HER2- breast cancers, a Ki67 level of expression >= 20% was predictive of benefit from adjuvant chemotherapy. A threshold at 14% was not as discriminant. Based on this large cohort study, we recommend the use of a cut-off at 20% to decide whether patientes with ER positive tumors should receive chemotherapy or not/. Citation Format: Rouzier R, Rossi L, Lerebours F, Savignoni A, Falcou M-C, Bonneau C, Pierga J-Y, Guinebretiere J-M. Ki67 cut-off point to predict the benefit of adjuvant chemotherapy in ER+ HER2- breast cancer patients. [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 P3-07-63.