JULIE GRALOW, MD, FASCO, Director of Breast Medical Oncology for the Seattle Cancer Care Alliance and Professor of Medical Oncology at the University of Washington School of Medicine, commented on the findings of the SUCCESS A trial in an interview with The ASCO Post.
Julie Gralow, MD, FASCO
The Oxford meta-analysis showed that adjuvant bisphosphonates, at least in postmenopausal patients, not only reduce the incidence of fractures, but also reduce the risk for cancer recurrence and death,1 she noted. But the optimal duration of bisphosphonate therapy has been unclear. Studies of these drugs have ranged from 2 to 5 years, but none has compared duration of treatment, “so it’s a bit open-ended,” she said. Guidelines issued in 2017 by ASCO and Cancer Care Ontario stated only that postmenopausal women undergoing systemic treatment for early breast cancer should receive a bisphosphonate but did not specify duration.2
Study Limitations Noted
DR. GRALOW felt the study population may not represent those women who would derive the most benefit from adjuvant bisphosphonates; thus, the findings are not as helpful as they might be. The study included only patients who were getting chemotherapy, 58% being postmenopausal and only 70% hormone receptor–positive. “This was not your typical patient who you would think has the highest likelihood of getting bone metastases or benefitting from adjuvant bisphosphonates,” she pointed out, suggesting many postmenopausal, estrogen receptor– positive patients do not generally receive chemotherapy at all.
The analysis was also performed at 4 years, an early time point by which few events had occurred. “So there’s not power to see a difference between the treatment durations. It’s a short analysis, in a population of women many of whom are probably not going to benefit most from bisphosphonates,” she said.
“I do think this is an important study,” Dr. Gralow acknowledged. “But I don’t think it’s definitive. We haven’t solved the question of 2 vs 5 years for the women most likely to meet the criteria for adjuvant bisphosphonates.”
Dr. Gralow would recommend that a patient with osteoporosis or who is on an aromatase inhibitor, which can accelerate bone loss, continue the bisphosphonate for the duration of endocrine therapy. For the patient with strong bone mineral density who is not on an aromatase inhibitor, “I would say a shorter duration is fine,” she said. “I think treatment needs to be tailored. We need to use our clinical judgment.” ■
DISCLOSURE: Dr. Gralow has served as a consultant for Genentech/Roche, Novartis, Merck, Pfizer, Sandoz, Puma, and AstraZeneca.
1. Early Breast Cancer Trialists’ Collaborative Group (EBCTCG): Adjuvant bisphosphonate treatment in early breast cancer: Meta-analyses of individual patient data from randomized trials. Lancet 386:1353-1361, 2015.
2. Dhesy-Thind S, Fletcher GG, Blanchette PS, et al: Use of adjuvant bisphosphonates and other bone-modifying agents in breast cancer: A Cancer Care Ontario and American Society of Clinical Oncology Clinical Practice Guideline. J Clin Oncol 35:2062-2081, 2017.
THE PHASE III SUCCESS A trial, presented at the 2017 San Antonio Breast Cancer Symposium, found no benefit for extending the use of intravenous zoledronic acid from 2 years to 5 years.1
“At this time point, our study showed no difference in disease-free survival or overall survival between 5 years ...