SAN ANTONIO – Adjuvant therapy with ibandronate made no impact on disease-free survival or overall survival rates in women with node-positive, early breast cancer that had been treated with dose-dense chemotherapy in a phase-III study of more than 3,000 patients.
The 3-year disease-free survival rate of 87.6% in those on ibandronate (Boniva) was a close match with the 87.2% that was recorded in a control group under observation. The 3-year overall survival rates also were similar, at 94.7% with ibandronate and 94.1% with observation.
There were no differences in disease-free survival for any of the subgroup analyses, Volker Möbus, Ph.D., reported at the annual San Antonio Breast Cancer Symposium.
"The interim analysis for efficacy showed little difference between treatment arms with and without ibandronate," said Dr. Möbus, head of obstetrics and gynecology at Klinikum Frankfurt (Germany) Höchst. The interim analysis was planned when 50% (405) of the expected events had been reached.
The GAIN (German Adjuvant Intergroup Node-Positive Study) trial is a controlled, nonblinded, randomized, phase III trial. The investigators compared epirubicin, cyclophosphamide, and paclitaxel chemotherapy with epirubicin and cyclophosphamide followed by paclitaxel and capecitabine. In addition, patients were further randomized in a 2:1 ratio to receive ibandronate (50 mg/day for 2 years) or observation alone.
Dr. Möbus presented the results for the ibandronate component of the trial. The chemotherapy results have not been released.
The GAIN trial randomized 3,023 women between June 2004 and August 2008. The protocol required that they be aged from 18 to younger than 65 years, and have histologically confirmed, lymph node–positive uni- or bilateral primary breast cancer, as well as an ECOG performance score of at least 2. Patients could have no distant metastases, and a life expectancy of at least 10 years was required. The median age was 50 years, and median follow-up was 39 months.
In all, 2,015 and 1,008 patients, respectively, were randomized to ibandronate vs. observation. However, 15 patients in the observation arm also started ibandronate, for a total of 1,870 patients. Some 18% of patients on ibandronate discontinued use of the drug for a variety of reasons, including death, adverse events, and loss to follow-up, noted Dr. Möbus.
An oral bisphosphonate, ibandronate is approved for the prevention and treatment of osteoporosis in postmenopausal women in the United States.
Financial support for the study was provided by Amgen and Roche. Dr. Möbus and several of his coinvestigators disclosed financial relationships with Amgen and Roche.