A secondary analysis of the phase 3 SOLD trial reveals that one year of adjuvant trastuzumab (Herceptin) significantly improves disease-free survival (DFS) in patients with ERBB2-positive breast cancer compared to a 9-week regimen when administered with chemotherapy. The findings, published in JAMA Network Open, highlight the importance of treatment duration in managing this aggressive form of breast cancer, although overall survival (OS) rates were similar between the two groups.
The study enrolled 2176 women aged 18 years or older with early ERBB2-positive breast cancer. Patients were randomized to receive either 9 weeks or 1 year of trastuzumab in conjunction with chemotherapy. The chemotherapy regimen consisted of 3 cycles of intravenous docetaxel (80 mg/m2 or 100 mg/m2) followed by 3 cycles of intravenous fluorouracil (600 mg/m2), epirubicin (75 mg/m2), and cyclophosphamide (600 mg/m2). The primary objective was to assess DFS, with secondary objectives including distant DFS and OS.
Disease-Free and Overall Survival
The 5-year DFS rate was 90.7% in the 1-year group and 87.7% in the 9-week group. At 10 years, the DFS was 80.3% in the 1-year group and 78.6% in the 9-week group. While the 1-year regimen demonstrated superior DFS, the overall survival rates at 5 and 10 years were comparable between the two groups (5-year OS: 95.9% vs 95.0%; 10-year OS: 88.2% vs 89.1%).
Risk Factors and Tolerability
Multivariable analysis identified that the number of positive axillary nodes (HR, 2.77; 95% CI, 1.79-4.30; P < .001), age at study entry (HR, 1.03; 95% CI, 1.01-1.05; P < .001), and disease stage (HR, 1.93; 95% CI, 1.22-3.03; P = .005) were independently associated with the risk of death. Interestingly, estrogen receptor (ER) status, treatment group, or docetaxel starting dose were not associated with the risk of death (HR, 1.22; 95% CI, 0.90-1.64; P = .20).
According to the study authors, "Potential advantages of the 9-week regimen include little need for cardiac monitoring, fewer visits required for treatment administration, and lower cost. Access to trastuzumab is still a major barrier to care, particularly in low-income and lower-middle-income countries."
Limitations
The study's limitations include a potentially short follow-up time, which may have affected the capture of all recurrence events and breast cancer-related deaths. Additionally, a significant proportion of patients (59.6%) had node-negative cancer, which may limit the generalizability of the findings.
