Abstract P1-10-01: Safety and efficacy of neoadjuvant metformin with trastuzumab and chemotherapy in women with HER2-positive early breast cancer: A randomized, open-label, multicenter, phase 2 trial

Abstract

Abstract Background: Epidemiological, pre-clinical, and window-of-opportunity trials have suggested that the anti-diabetic drug metformin (MET) may have beneficial effects on breast cancer (BC). The clinical relevance of combining MET with current standards of care for first-line treatment of BC is unknown. We investigated the safety and efficacy of adding MET to neoadjuvant chemotherapy plus trastuzumab (TTZ) in patients with HER2-positive early BC. Methods: In a randomized, multicenter, open-label phase 2 study, women with operable, locally advanced, or inflammatory HER2+ BC were randomly assigned in a 1:1 ratio to receive daily MET (1,700 mg) for 24 weeks concurrently with 12 cycles of weekly paclitaxel plus TTZ followed by four cycles of fluorouracil, epirubicin, cyclophosphamide/3w plus TTZ (arm A) or equivalent sequential chemotherapy plus TTZ without MET (arm B), followed by surgery. Patients were stratified by age, extent of disease (cT2 cN0-1 vs ≥ T3 or ≥ N2), and hormone receptor (HR)-status. The intention-to-treat (ITT) safety population comprised all women who underwent randomization and received at least one treatment dose. Primary endpoint was the rate of pathological complete response (pCR) analyzed in the per-protocol (PP) efficacy population. pCR was defined as absence of invasive cancer in the breast and axillary nodes, irrespective of carcinoma in situ (ypT0/is ypN0). Results: From June 1, 2012 to March 17, 2016, 98 patients were assessed for eligibility at 10 centers in Spain. Of 84 (85.7%) patients who were randomized, 41 patients were allocated to arm A and 43 to arm B. The most common adverse effects (AEs) in the 79 ITT patients were fatigue, diarrhea, nausea, alopecia, sensory neuropathy, mucositis, neutropenia, and elevated AST/ALT. Most AEs were grades 1–2 (>90% in both arms). The most common AEs grade ≥3 were neutropenia (7/38 women in arm A and 5/41 women in arm B) and diarrhea (5 and 0, respectively). The number of serious AEs was 3 in arm A (none of them was deemed to be MET-related) and 2 in arm B. At week 12, one (2.9%) patient in arm A and 6 (15%) in arm B exhibited asymptomatic decreases in the left ventricular ejection fraction (LVEF). At week 24, none (0%) of the patients in arm A and 3 (7.9%) patients in arm B presented decreases of LVEF below 50% and >10% from baseline. Only one patient (2.7%) in arm B experienced symptomatic heart failure. The rates of breast-conserving surgery were 79.3% and 58.6% in PP arms A and B, respectively. Also, 19/29 PP patients in arm A (65.5%, 95% CI 47–80) had a pCR versus 17/29 PP patients (58.6%, 95% CI 41–74) in arm B (OR 1.34 [95% CI 0.46–3.89], p=0.589). The combined rates of pCR and near-pCR (ypT1aN0) were 79.3% in arm A and 72.4% in arm B. Significantly fewer pCR were noted for tumors that were HR-positive regardless of which arm the patients were randomized. Conclusion: The higher pCR rate in HER2+ BC patients receiving MET-containing neoadjuvant therapy and TTZ did not reach statistical significance. Evaluation of long-term outcome data such as 5-year disease-free survival and correlative biological studies are needed to evaluate the clinico-molecular relevance of these findings. Citation Format: Pernas S, Dorca J, Álvarez-López I, Martínez S, Saura C, Batista López N, Rodríguez-Sánchez CA, Amillano K, Domínguez-Fernández S, Luque Cabal M, Morilla I, Viñas G, Cortés J, Cuyàs E, Verdura S, Fernández-Arroyo S, Joven J, Pérez E, García M, Bosch N, López-Bonet E, Saidani S, Buxó M, Menendez JA, Martin-Castillo B. Safety and efficacy of neoadjuvant metformin with trastuzumab and chemotherapy in women with HER2-positive early breast cancer: A randomized, open-label, multicenter, phase 2 trial [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-10-01.