45 Use of Preoperative Ultra-Hypofractionated Radiotherapy in Patients With Locally Advanced Breast Cancer: Clinical and Pathological Outcomes

Introduction

Management of locally advanced breast cancer remains a significant therapeutic challenge, particularly in patients with extensive disease or limited initial surgical options. Preoperative radiotherapy has been extensively researched as a treatment strategy; however, evidence supporting ultra-hypofractionated regimens remains scarce. Therefore, our aim is to report the experience of a Chilean oncology center implementing preoperative 5-fraction regimen radiotherapy in patients with locally advanced breast cancer.

Objective

To evaluate clinical and pathological response outcomes in patients with locally advanced breast cancer treated with preoperative radiotherapy using a 5-fraction regimen.

Materials and Methods

A retrospective review of medical records from May 2022 to May 2025 was conducted. Patients with breast cancer who received preoperative radiotherapy with a total dose of 26 Gy delivered in 5 fractions to the breast and regional lymph nodes were included. Among 987 patients treated during this period, 45 received preoperative radiotherapy and were included in this study.

Results

Preoperative staging showed that 88.9% of patients were classified as cT4, while 11.1% were cT2. Nodal status was 15.6%, 20%, 46.7% and 17.8% for cN3, cN2, cN1, and cN0, respectively. Four patients had metastatic disease (stage IV). Regarding biological subtype, 80% were hormone receptor-positive, 4.4% were HER2-positive, and 13.3% were triple-negative. Neoadjuvant chemotherapy was administered to 71.1% of patients.

Radiotherapy was delivered with curative-intent in 88.9% of cases and with palliative intent in 11.1%.

Of the 45 treated patients, 66.7% (n = 30) attended one or more follow-up visits at the treating center, with a median follow-up of 11.5 months. At the time of analysis, 68.9% of the study population remained alive.

Forty-two percent of patients (n = 19) underwent surgery (total mastectomy with axillary lymph node dissection in all patients); however, surgical pathology reports were available for only 14 patients. Among these, a reduction in tumor size and nodal involvement consistent with clinical downstaging was observed in 92.9% of cases.

After radiotherapy, favorable clinical response (partial or complete response) was observed in 46.6% of patients, while 15.5% showed disease progression and 4.4% no clinical response. Evaluation was not feasible in 33.3% due to loss to follow-up.

Conclusion

Preoperative radiotherapy using ultra-hypofractionated regimens delivered in 5 fractions may represent a feasible and effective therapeutic option for patients with locally advanced breast cancer in both curative and palliative settings. Although the current evidence remains limited, these preliminary findings suggest potential clinical benefit, particularly for patients with extensive disease or tumors initially unsuitable for surgical management.