BACKGROUND: Elderly breast cancer patients are affected by poorer quality of life (QoL) compared to younger patients. Because QoL has a relevant impact on guideline-adherent treatment, elderly breast cancer patients are often undertreated, especially with regard to adjuvant chemotherapy, and overall survival is decreased. Thus, understanding the impact of chemotherapy on QoL in elderly patients is crucial. This study compared QoL in patients aged < 65 years and 65 to 70 years receiving adjuvant chemotherapy as a secondary outcome in the prospective randomized multicenter ADEBAR trial. PATIENTS AND METHODS: Patients with lymph node-positive breast cancer were prospectively randomized for either sequential anthracycline-taxane or epirubicin/fluorouracil/cyclophosphamid chemotherapy (FEC) therapy. QoL was assessed at baseline (t1), before cycle 4 FEC, and cycle 5 epirubicin/cyclophosphamid-docetaxel (EC-DOC) (t2), 4 weeks after chemotherapy (t3), and 6 weeks after radiation (t4) using the European Organization for Research and Treatment for Cancer (EORTC) Quality of Life Core Questionnaire (QLQ-C30) and the Breast Cancer-Specific Module (QLQ-BR23). We compared patients aged < 65 years and 65 to 70 years with respect to QoL and discontinuation of chemotherapy. RESULTS: A total of 1363 patients were enrolled onto the ADEBAR trial, with 16.7% of the patients aged 65 to 70 years. In elderly patients, Eastern Cooperative Oncology Group performance status was higher and global health status and physical functioning were lower at baseline. Global health status decreased between t1 and t3 by 7 points in patients < 65 years and by 11 points in patients 65 to 70 years, and physical functioning decreased in the same period by 13.4 points in patients aged < 65 years and by 15.9 points in patients 65 to 70 years. In both groups, at t4 global health status exceeded baseline by 6 points, and physical functioning was 1.3 points under baseline in patients < 65 years old and 3 points under baseline in patients 65 to 70 years. There was a trend to more fatigue in elderly patients and to more nausea and vomiting while receiving chemotherapy in younger patients at t3. There was a higher dropout rate in patients aged 65 to 70 years (25.7%) than in patients aged < 65 years (16.2%). CONCLUSION: There were only small or trivial differences in QoL in patients aged < 65 years versus 65 to 70 years who were receiving adjuvant chemotherapy, although the dropout rate from chemotherapy was notably higher in elderly breast cancer patients.