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Preoperative partial breast irradiation (PBI) can result in an increased accuracy of target volume definition and decreased irradiated volumes compared with postoperative PBI. In the multicenter ABLATIVE trial (NCT02316561), 15/36 patients achieved pathologic complete response 6-8 months after preoperative single-dose PBI. We now present long-term outcomes of preoperative single-dose PBI and breast conserving surgery (BCS) including late toxicity, tumor recurrence, survival, cosmetic outcome and quality of life in low-risk breast cancer patients.

Between 2015 and 2018, 36 patients were treated with preoperative single-dose PBI followed by BCS after 6 (n=15) or 8 (n=21) months. The gross tumor volume (GTV), which is the breast tumor on MRI, and clinical target volume (CTV) (GTV+2cm) were expanded by a 3 mm planning target volume (PTV) margin. The prescribed dose was 20 Gy to PTV-GTV, and 15 Gy to PTV-CTV. Toxicity was scored at baseline and yearly visits until 5 years after PBI according to the Common Terminology Criteria for Adverse Events, and cosmetic outcome was assessed by patient and physician. Quality of life was evaluated yearly until 4 years after PBI using the European Organization for Research and Treatment of Cancer QLQ-C30 and BR23 questionnaires, and the Hospital Anxiety and Depression Scale. Changes in cosmetic outcome and quality of life scores from baseline over time were analyzed using linear mixed models.

All  women were aged ≥ 50 years and had invasive, unifocal, non-lobular breast cancer, estrogen receptor-positive, HER2-negative, and a tumor negative sentinel node. Median tumor size on MRI was 13 mm (range: 5-20 mm). After a median follow-up of 5.1 years (3.8–6.3 years), grade 1 breast fibrosis and breast discomfort/pain were present in 83% and 44% of the patients, respectively (table 1). Grade 2 breast fibrosis (3%) and fatigue (3%) at 3 years completely resolved at 5 years. Two (6%) patients developed ipsilateral breast events (DCIS (n=1) and invasive lobular carcinoma (n=1)) and two (6%) distant metastases. Five-year disease-free and overall survival rates were 89% and 94%, respectively. Shortly after BCS at 12 months, the proportion of patients (very) satisfied with the cosmetic results decreased from 89% (baseline) to 63%, before improving to 76% at 5 years (p=0.7) (fig. 1). Physicians rated the cosmetic result as excellent/good in 80% of the patients at 5 years versus 97% at baseline (p=0.4). The 4-year median QLQ-C30 and BR-23 scores were 93 (57-100) and 88 (68-99) respectively, with no change from baseline (p=1.0; p=0.5). Median anxiety and depression scores remained constant over 4 years (p=0.1; p=0.7).

Preoperative single-dose PBI and BCS is a safe treatment with acceptable oncological outcomes, mild late toxicity, and satisfactory cosmetic results and quality of life at 5 years of follow-up. In the ongoing ABLATIVE-2 trial (NCT05350722), BCS is performed at a longer interval of 12 months after preoperative PBI.