SABCS 2016: Adding Ibandronate to Hormone Therapy Did Not Improve Outcomes for Postmenopausal Breast Cancer Patients
Postmenopausal women with hormone receptor–positive early-stage breast cancer who received the bisphosphonate ibandronate (Boniva) in addition to adjuvant hormone therapy did not have improved disease-free survival outcomes, according to data from the phase III clinical trial TEAM IIB presented at the 2016 San Antonio Breast Cancer Symposium, held December 6–10 (Abstract S6-02).
However, a nonsignificant improvement in disease-free survival and reduction in the number of patients developing bone metastasis was observed after 3 years of therapy among those who received ibandronate, leading the trial investigators to conclude that a longer follow-up may be required to draw definitive conclusions.
“Data from TEAM IIB showed that postmenopausal women who received ibandronate for 3 years along with hormone therapy had a trend toward improved [disease-free survival] outcome that was statistically insignificant,” said Sabine Linn, MD, PhD, a medical oncologist in the Department of Molecular Pathology at the Netherlands Cancer Institute.
“We recently reached the required number of [disease-free survival] events that would help determine conclusive evidence of benefit (or no benefit) from adding ibandronate,” Dr. Linn added.
Hormonal therapy usually consists of aromatase inhibitors, which have a negative effect on bone health. About 70% of postmenopausal breast cancer patients who develop metastatic disease experience bone metastasis, and it has a major influence on length and quality of life for these patients, as they suffer from pain and immobility, explained Sonja Vliek, MD, a resident medical oncology and PhD student working with Dr. Linn. Prevention of bone metastases is therefore a major topic in breast cancer research, she added.
TEAM IIB Findings
In TEAM IIB, 1,116 postmenopausal women with early-stage breast cancer were enrolled in 37 hospitals in the Netherlands and randomly assigned 5 years of hormonal therapy with or without 50 mg ibandronate daily, for 3 years. The primary endpoint was disease-free survival, and secondary endpoints included safety, overall survival, time to bone metastasis, and other sites of recurrence.
Median follow-up was 4.6 years, and 67% of patients in the test arm adhered to ibandronate treatment for 3 years.
As of November 2016, 149 disease-free survival events had been reported. The 3-year disease-free survival rate in the ibandronate arm was 94.3%, vs 90.8% in the control arm, with a nonsignificant 20% improvement in disease-free survival in the ibandronate arm.
Three years after randomization, 1.6% and 4.7% of patients in the ibandronate and control arms, respectively, developed bone metastasis; those in the ibandronate arm were 35% less likely to have bone metastasis, but this finding was not statistically significant.
There were 36 serious adverse events reported in 31 patients from the ibandronate arm and 51 serious adverse events reported in 39 patients from the control arm. The only serious adverse event reported for ibandronate was osteonecrosis of the jaw, which in all patients resolved without complaints after treatment, according to Dr. Vliek.
“If the results from this trial are considered along with results from the EBCTCG meta-analysis, in which a modest benefit of overall survival was observed for postmenopausal women by adding a bisphosphonate to standard adjuvant systemic therapy, the evidence to treat postmenopausal women with early breast cancer with adjuvant bisphosphonate increases,” said Dr. Linn.
“Patients should discuss this adjuvant treatment with their physicians to outweigh the possible side effects from the possible gain in survival,” she added.
Further analyses of the data are planned as soon as the last patient reaches the 3-year follow-up period (May 2017), Dr. Vliek noted. The investigators plan to follow the patients for up to 10 years to analyze the long-term effects.
Limitations of the study include that it was not placebo-controlled and was possibly underpowered, Dr. Vliek said.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
