Thomas W. P. Friedl, PhD1; Tanja Fehm, MD2; Volkmar Müller, MD3; et alWerner Lichtenegger, MD4; Jens Blohmer, MD5; Ralf Lorenz, MD6; Helmut Forstbauer, MD7; Visnja Fink, MD1; Inga Bekes, MD1; Jens Huober, MD1; Julia Jückstock, MD8; Andreas Schneeweiss, MD9; Hans Tesch, MD10; Sven Mahner, MD8; Sara Y. Brucker, MD11; Georg Heinrich, MD12; Lothar Häberle, PhD13; Peter A. Fasching, MD13; Matthias W. Beckmann, MD13; Robert E. Coleman, PhD14; Wolfgang Janni, MD1; Brigitte Rack, MD1
JAMA Oncol. Published online June 24, 2021. doi:10.1001/jamaoncol.2021.1854
Question Does extended adjuvant treatment with zoledronate for 5 years provide a survival benefit for patients with early breast cancer compared with 2 years of zoledronate treatment?
Findings In the randomized phase 3 SUCCESS A clinical trial, no statistically significant difference in survival between 5 and 2 years of adjuvant zoledronate treatment could be shown in 2987 patients with early breast cancer, irrespective of menopausal status. The frequency of adverse events was higher with 5 years of zoledronate treatment—both all grades and grades 3 or 4 only.
Meaning The results of this randomized clinical trial suggest that the recommended 3 to 5 years of adjuvant bisphosphonate treatment for patients with high-risk early breast cancer as published in current clinical guidelines could be reduced.
Importance Bisphosphonate treatment in patients with early breast cancer has become part of care, but the optimal treatment duration is still unclear.
Objective To compare 2 vs 5 years of zoledronate treatment following adjuvant chemotherapy in patients with early breast cancer.
Design, Setting, and Participants The SUCCESS A phase 3 multicenter randomized open-label clinical trial with a 2 × 2 factorial design enrolled 3754 patients from September 21, 2005, to March 12, 2007 (last patient out, May 7, 2014). Final data analysis was conducted from September 2019 to October 2020. In 250 German study centers, patients were eligible for participation in the SUCCESS A trial if they had either node-positive or high-risk node-negative (defined as at least 1 of the following: tumor size ≥ pT2, histologic grade 3, negative hormone receptor status, or age ≤35 years) primary invasive breast cancer.
Interventions Patients were first randomized to adjuvant chemotherapy with 3 cycles of fluorouracil, epirubicin, and cyclophosphamide followed by 3 cycles of docetaxel with or without gemcitabine (not presented in this report). After chemotherapy, patients underwent a second randomization of 5 years of zoledronate treatment (4 mg intravenously every 3 months for 2 years, followed by 4 mg intravenously every 6 months for 3 years) vs 2 years of zoledronate treatment (4 mg intravenously every 3 months for 2 years).
Main Outcomes and Measures The primary end point of the study was disease-free survival; secondary end points were overall survival, distant disease-free survival, and the incidence of skeletal-related adverse events. Survival times were measured from 2 years after the start of zoledronate treatment (landmark analysis).
Results Overall, data on 2987 patients were available for analysis; median age was 53 (range, 21-86) years. Disease-free survival, overall survival, and distant disease-free survival did not differ significantly between the 2 treatment arms (5 vs 2 years) as shown by adjusted multivariable Cox proportional hazards regression models (disease-free survival: hazard ratio [HR], 0.97; 95% CI, 0.75-1.25; P = .81; overall survival: HR, 0.98; 95% CI, 0.67-1.42; P = .90; distant disease-free survival: HR, 0.87; 95% CI, 0.65-1.18; P = .38). Adverse events were observed more often in the 5-year (46.2%) vs 2-year (27.2%) zoledronate treatment arm, which was particularly true for the skeletal-related events bone pain (5 years, 8.3% vs 2 years, 3.7%) and arthralgia (5 years, 5.1% vs 2 years, 3.1%).
Conclusions and Relevance The results of this phase 3 randomized clinical trial indicate that extending the zoledronate treatment beyond 2 years does not improve the prognosis of high-risk patients with early breast cancer receiving chemotherapy, suggesting that the currently recommended bisphosphonate treatment duration of 3 to 5 years could be reduced.