Safety and efficacy of targeted intraoperative radiotherapy (TARGIT) for early breast cancer: First report of a randomized controlled trial at 10-years maximum follow-up.

LBA517 Background: After breast conserving surgery, 90% of local recurrences (LR) occur within the index quadrant. Hence, restricting the radiation therapy to the immediate area around the tumour bed after removal of the primary tumour may be adequate (Vaidya JS, et al. Br Cancer.1996;74:820-4) Methods: Having safely piloted a new technique of partial breast irradiation (Vaidya JS, Baum M, Tobias JS et al Ann Oncol 2001;12:1075-80) we launched the TARGIT-A trial in March 2000 comparing TARGIT vs. standard whole breast external beam radiotherapy (EBRT) after breast conserving surgery in patients ≥45 years with invasive duct carcinoma. LR was the primary outcome measure (core protocol: www.thelancet.com/protocol-reviews/99PRT-47). Trial accrual from 31 international centers is complete (n=2232), with 80% power to detect a difference in relapse rate of 2.5% - the non-inferiority margin. Results: Median age was 63 (IQR 57-69), median tumor size 13mm (IQR 9-18mm), lymph nodes 17%+ve. Median follow-up is 24.6 m...