As reported by Joensuu et al in JAMA Network Open, long-term follow-up of the European SOLD trial indicates the addition of adjuvant trastuzumab to chemotherapy for 9 weeks vs 1 year continued to show poorer disease-free survival in patients with HER2-positive breast cancer, with no difference in overall survival observed.
Study Details
In the open-label trial, 2,174 patients from sites in seven European countries were randomly assigned between January 2008 and December 2014 to receive adjuvant chemotherapy plus 9 weeks of trastuzumab (n = 1,085) or 1 year of trastuzumab (n = 1,089). Chemotherapy consisted of three cycles of docetaxel at 3-week intervals followed by three cycles of fluorouracil, epirubicin, and cyclophosphamide at 3-week intervals.
Trastuzumab was administered in both groups for 9 weeks concomitantly with docetaxel. In the 9-week group, no trastuzumab was given after chemotherapy; in the 1-year group, trastuzumab was continued to complete 1 year of treatment.
Key Findings
Median follow-up in the current analysis was 8.1 years (interquartile range = 8.0–8.9 years). The trastuzumab 9-week group had significantly poorer disease-free survival vs the 1-year group (hazard ratio [HR] = 1.36, 90% confidence interval [CI] = 1.14–1.62, P = .004); the 5- and 10-year disease-free survival rates in the 1-year group vs the 9-week group were 90.7% vs 87.7% and 80.3% vs 78.6%.
No significant difference in overall survival was observed between the 9-week group vs the 1-year group (HR = 1.20, 90% CI = 0.94–1.54, P = .22); the 5- and 10-year overall survival rates in the 1-year group vs the 9-week group were 95.0% vs 95.9% and 89.1% vs 88.2%. No significant difference between the 9-week group vs the 1-year group was observed in distant disease–free survival (HR = 1.28, 90% CI = 1.00–1.65, P = .10).
On multivariate analysis, the 9-week group had significantly poorer disease-free survival (HR = 1.36, 95% CI = 1.10–1.68, P = .005), with no significant difference in overall survival observed (HR = 1.22, 95% CI = 0.90–1.64, P = .20).
Death as a result of cardiac causes was infrequent, occurring in a total of four patients (0.2%).
The investigators concluded: “In this secondary analysis of a randomized clinical trial, 1-year vs 9-week adjuvant trastuzumab was associated with improved [disease-free survival] among patients with [HER2-positive] breast cancer receiving chemotherapy, but there was no significant difference in overall survival between the groups.”
Heikki Joensuu, MD, PhD, of the Department of Oncology, Helsinki University Hospital and University of Helsinki, Finland, is the corresponding author of the JAMA Network Open article.
DISCLOSURE: The study was supported by Pharmac (New Zealand), Sanofi, Novartis, Cancer Society of Finland, Helsinki University Hospital research funds, and others. For full disclosures of the study authors, visit jamanetwork.com.
