Phase III evaluating the addition of fulvestrant (F) to anastrozole (A) as adjuvant therapy in postmenopausal women with hormone receptor-positive HER2-negative (HR+/HER2−) early breast cancer (EBC): results from the GEICAM/2006–10 study

Abstract

GEICAM/2006-10 compared anastrozole (A) versus fulvestrant plus anastrozole (A + F) to test the hypothesis of whether a complete oestrogen blockade is superior to aromatase inhibitors alone in breast cancer patients receiving hormone adjuvant therapy. Multicenter, open label, phase III study. HR+/HER2- EBC postmenopausal patients were randomized 1:1 to adjuvant A (5years [year]) or A + F (A plus F 250mg/4weeks for 3year followed by 2year of A). Stratification factors: prior chemotherapy (yes/no); number of positive lymph nodes (0/1-3/≥ 4); HR status (both positive/one positive) and site. disease-free survival (DFS). Planned sample size: 2852 patients. The study has an early stop due to the financer decision with 870 patients (437 randomized to A and 433 to A + F). Patient characteristics were well balanced. After a median follow-up of 6.24y and 111 DFS events (62 in A and 49 in A + F) the Hazard Ratio for DFS (combination vs. anastrozole) was 0.84 (95% CI 0.58-1.22; p = 0.352). The proportion of patients disease-free in arms A and A + F at 5year and 7year were 90.8% versus 91% and 83.6% versus 86.7%, respectively. Most relevant G2-4 toxicities (≥ 5% in either arm) with A versus A + F were joint pain (14.7%; 13.7%), fatigue (2.5%; 7.2%), bone pain (3%; 6.5%), hot flushes (3.5%; 5%) and muscle pain (2.8%; 5.1%). The GEICAM/2006-10 study did not show a statistically significant increase in DFS by adding adjuvant F to A, though no firm conclusions can be drawn because of the limited sample size due to the early stop of the trial. ClinicalTrials.gov: NCT00543127.