Adjuvant Trastuzumab Without Chemotherapy For Treating Early HER2-Positive Breast Cancer In Older Patients: A Cohort Study Accompanying With The RESPECT Trial

Purpose To gauge the effects of treatment practices on prognosis for all older patients with HER2-positive breast cancer, particularly to determine whether adjuvant trastuzumab alone can offer benefit over no adjuvant therapy. This report accompanies the RESPECT study, a randomized-controlled trial (RCT) comparing trastuzumab monotherapy with trastuzumab-plus-chemotherapy for early HER2-positive breast cancer.Patients and methods Patients who declined the RCT were treated based on the physician’s discretion. We studied the (1) trastuzumab-plus-chemotherapy group, (2) trastuzumab-monotherapy group, and (3) non-trastuzumab group (no therapy or anticancer therapy without trastuzumab). The primary endpoint was disease-free survival (DFS), which was compared using the propensity-score method.Results We enrolled 398 eligible patients, aged over 70 years, with HER2-positive invasive breast cancer, of whom 275 (69%) were in the RCT, and 123 (31%) were in this cohort group. The median age was 74.5 years. Among cohort group treatment categories were as follows: (1) trastuzumab-plus-chemotherapy group (n = 36, 30%), (2) trastuzumab-monotherapy group (n = 52, 43%), and (3) non-trastuzumab group (n = 32, 27%). A total of 73% of patients received trastuzumab-containing regimens, with or without chemotherapy. The 3-year DFS was 92.3% in the trastuzumab-plus-chemotherapy group, 89.2% in the trastuzumab-monotherapy group, and 82.5% in the non-trastuzumab group. DFS in the non-trastuzumab group was lower than in the trastuzumab-plus-chemotherapy and trastuzumab-monotherapy groups (propensity-adjusted HR: 3.29; 95% CI: 1.15–9.39; P = 0.026). The relapse-free survival in the non-trastuzumab group was lower than in the trastuzumab-plus-chemotherapy and trastuzumab monotherapy groups (propensity-adjusted HR = 7.80; 95% CI: 2.32–26.2, P < 0.0001). Chemotherapy with trastuzumab or trastuzumab monotherapy did not affect health-related quality of life (HRQoL) at 36 months.Conclusions Trastuzumab-treated patients had better prognoses than patients not treated with trastuzumab without deterioration of HRQoL. Thus, trastuzumab monotherapy can be considered for patients who reject chemotherapy.Trial registration number The protocol was registered on the website of the University Hospital Medical Information Network (UMIN), Japan (protocol ID: UMIN 000028476).