S2-4: GAIN Study: A Phase III Trial To Compare ETC vs. EC-TX and Ibandronate vs. Observation in Patients with Node-Positive Primary Breast Cancer – 1st Interim Efficacy Analysis.
Authors: V Möbus, IJ Diel, N Harbeck, D Elling, C Jackisch, C Thomssen, M Untch, B Conrad, A Schneeweiss, R Kreienberg, J Huober, V Müller, H-J Lück, I Bauerfeind, S Loibl, V Nekljudova, G von Minckwitz
Journal: Cancer Research (2011)

Abstract Background: We previously showed that intense dose-dense (idd) epirubicin (E), paclitaxel (T), cyclophosphamide (C) results in a superior DFS and OS compared to conventionally dosed EC-T in pts with primary breast cancer (PBC) and ≥4 involved lymph nodes (LN) (Möbus et al JCO 2010). In the GAIN study, the intense dose-dense strategy has been further investigated as well as the adjuvant application of ibandronate (I). We here report on the planned interim efficacy analysis after 50% (N&amp;gt;401) of the required events have occurred. Methods: A prospective, multi-center, controlled, non-blinded, randomized phase III trial investigating ETC (E: 150 mg/m2, T:225 mg/m2, C:2500–2000 mg/m2, i.v. day 1, q15 for 3 cycles each: A1); or EC→TX (E: 112.5 mg/m2 + C: 600 mg/m2, i.v. day 1, q 15 for 4 cycles→T: 67.5 mg/m2 i.v. day 1, q 8 for 10 weeks + X: 2000 mg/m2 p. o. day 1–14, q 22 for 4 cycles: A2). Pts were further randomized in a 2:1 ratio to receive ibandronate: 50 mg/day p.o. for 2 years (B1) or observation (B2). Pts received a primary prophylaxis with either epoetin β or darbepoetin α and pegfilgrastim during ETC or EC. After recruitment of 1500 pts prophylactic ciprofloxacin was implemented and the dose of C was reduced to 2000 mg/m2. Eligibility: Females ≥18 and &amp;lt;65 years, histologically confirmed LN positive uni- or bilateral PBC; adequate surgery, ≥1 pos.LN; ECOG ≤2; written informed consent. Primary objective:compare DFS A1 vs. A2 and B1 vs.B2. Secondary objectives: OS, safety, incidence of secondary primaries, and EFS in subgroups of hormone sensitivity and number of pos. LN between arms; assessment of compliance; determine prognostic factors. 3000 pts with 801 events were needed to show an increase of 5-year DFS from 75% to 79% for pts receiving EC→TX and 728 events to show an increase of 5-year DFS from 75% to 79.5% for pts receiving I, assuming a drop-out rate of 5%, α=0.05 (two-sided)and 1-β =80%. An interim analysis for both primary objectives was planned after 50% of the expected events occurred. Safety results have been reported previously (Möbus et al. SABCS 2009). Results: 3023 patients were randomized between 06/2004 and 08/2008.1512 received ETC and 1511 EC→TX. 29pts never started therapy, 14 in ETC, 15 in EC→TX. Median follow-up is 38.7 months. Median age was 50 years; pN1 (37.7%), pN2 (35.4%); pN3 (26.9%); 77.4% had ductal invasive carcinoma, 46.6% were grade 3; 76.7% had hormone receptor-positive tumors, 22% were HER2−positive. 405 events have occurred by 12.05.2011.380pts relapsed and 25pts. died w/o relapse. The interim futility boundary for chemotherapy was not crossed. For the ibandronate question the futility boundary was reached. There was no difference in DFS and OS between the patients with and without ibandronate (DFS log-rank p=0.593; HR 1.059; 95%CI 0.861−1.301; OS log-rank p=0.801 HR 0.961; 95% CI 0.705−1.31). Conclusion: The GAIN study demonstrated that adjuvant ibandronate does neither improve DFS nor OS in primary node positive breast cancer after treatment with dose-intensified chemotherapy. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr S2-4.