Adjuvant Therapy for Elderly Breast Cancer Patients after Breast-Conserving Surgery: Outcomes in Real World Practice

SIMPLE SUMMARY: The treatment of elderly patients with breast cancer often deviates from guideline recommendations due to comorbidities, expected side effects, and patient preference. We investigated the standard of care of postoperative radiotherapy after breast-conserving surgery in elderly patients (≥65 years) treated outside of clinical trials, potential factors related to the omission of radiotherapy, and the interaction with endocrine therapy. Overall, three thousand one hundred seventy-one women treated at two major breast centers were evaluated. Postoperative radiotherapy was performed in 82% of these cases. The irradiated patients were younger and more likely to receive additional endocrine therapy and chemotherapy. Patients who did not receive radiotherapy were significantly more likely to have non-invasive DCIS tumors and did not undergo axillary surgery. Radiotherapy was associated with improved locoregional tumor control, even in patients receiving endocrine therapy. Patients treated with radiotherapy alone had significantly better locoregional control than with endocrine therapy alone. In conclusion, the present work confirms the efficacy of postoperative radiotherapy in the elderly, even in patients receiving endocrine therapy. ABSTRACT: We aimed to evaluate the standard of care of adjuvant radiotherapy (RT) after breast-conserving surgery (BCS) in elderly female patients (≥65 years) treated outside of clinical trials and to identify potential factors related to the omission of RT and the interaction with endocrine therapy (ET). All women treated with BCS at two major breast centers between 1998 and 2014 were evaluated. Data were provided by the Tumor Registry Munich. Survival analyses were conducted using the Kaplan–Meier method. Prognostic factors were identified using multivariate Cox regression analysis. The median follow-up was 88.4 months. Adjuvant RT was performed in 82% (2599/3171) of patients. Irradiated patients were younger (70.9 vs. 76.5 years, p < 0.001) and were more likely to receive additional chemotherapy (p < 0.001) and ET (p = 0.014). Non-irradiated patients more often had non-invasive DCIS tumors (pTis: 20.3% vs. 6.8%, p < 0.001) and did not undergo axillary surgery (no axillary surgery: 50.5% vs. 9.5%, p < 0.001). Adjuvant RT was associated with improved locoregional tumor control after BCS in invasive tumors (10-year local recurrence-free survival (LRFS): 94.0% vs. 75.1%, p < 0.001, 10-year lymph node recurrence-free survival (LNRFS): 98.1% vs. 93.1%, p < 0.001). Multivariate analysis confirmed significant benefits for local control with postoperative RT. Furthermore, RT led to increased locoregional control even in patients who received ET (10-year LRFS 94.8% with ET + RT vs. 78.1% with ET alone, p < 0.001 and 10-year LNRFS: 98.2% vs. 95.0%, p = 0.003). Similarly, RT alone had significantly better locoregional control rates compared to ET alone (10-year LRFS 92.6% with RT alone vs. 78.1% with ET alone, p < 0.001 and 10-year LNRFS: 98.0% vs. 95.0%, p = 0.014). The present work confirms the efficacy of postoperative RT for breast carcinoma in elderly patients (≥65 years) treated in a modern clinical setting outside of clinical trials, even in patients who receive ET.