Preoperative magnetic resonance guided single-dose partial breast irradiation: five-year results of the prospective single-arm ABLATIVE trial

BACKGROUNDPreoperative partial breast irradiation (PBI) can increase accuracy of target volume definition and decrease irradiated volumes compared with postoperative PBI. In the ABLATIVE trial (NCT02316561), 15/36 patients achieved pathologic complete response (pCR) 6-8 months after preoperative PBI and breast conserving surgery (BCS). We now present the 5-year results.METHODSThe ABLATIVE trial is a Dutch prospective cohort study in four hospitals. Women aged ≥ 50 years with unifocal, non-lobular breast cancer, ER-positive, HER2-negative, and a tumor negative sentinel node were treated between 2015-2018 with preoperative single-dose PBI followed by BCS after six or eight months. The primary endpoint was pCR. Secondary endpoints were yearly evaluated oncological outcomes, toxicity, cosmetic outcome (assessed by patients and physicians) and quality of life.RESULTSThirty-six patients were treated with BCS six (n=15) and eight (n=21) months following PBI. Median tumor size was 13 mm (IQR 9-16). After a median follow-up of 5.5 years (IQR 5.1–6.0 years), two (6%) patients had ipsilateral breast events and two (6%) distant metastases. The 5-years overall survival was 94% [95% CI 87-100%]. The 5-year cumulative incidence of clinician-reported grade 1/2 breast fibrosis and breast discomfort/pain were 94%/6% and 75%/6%, respectively. The proportion of patients (very) satisfied with the cosmetic results was 89% at baseline and 78% at 5 years. Cosmetic results evaluated using the BCCT.core software were excellent or good in all patients. The 4-year median global quality of life score was 83 (IQR 67-92), similar to baseline (83 (IQR 75-83), p=0.42).CONCLUSIONPreoperative single-dose PBI and BCS may be an oncologically safe treatment with mild late toxicity, and no decline in cosmetic results and quality of life during 5 years of follow-up. This means that preoperative instead of standard postoperative irradiation has the potential to challenge the current clinical practice.