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.

Abstract

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 months (max 10 years). Wound breakdown or delayed healing were reported in 28 of the TARGIT group and 20 in the EBRT group (p=0.24). RTOG grade 3 toxicity (nil grade 4) was seen in 6 vs. 21 (p=0.004) respectively. Overall local toxicity was equivalent (34/1092 TARGIT v. 41/1096 EBRT, p=0.42). The Kaplan-Meier estimate of LR in the breast, was 0.31% (CI 0.08-1.26) for TARGIT versus 0.29% for EBRT (CI 0.07-1.16) at 24 months. Conclusions: In the TARGIT group, the radiotherapy toxicity was significantly lower than in the EBRT group, while the increase in wound complications was not statistically significant. This analysis suggests that at a median follow-up of 24 months the local control with TARGIT is comparable to EBRT. Longer term follow-up is essential and accrual in similar studies is encouraged. [Table: see text]