OR time will tell.

Top Line: Is there a difference in long-term breast tumor recurrence between intraoperative radiation (IORT) and whole breast irradiation (WBI) for early stage breast cancer?

The Study: Two trials have compared IORT and WBI for women with early stage breast cancer: TARGIT and ELIOT. TARGIT used a photon-based technique while ELIOT used an electron technique. The initial results of ELIOT showed that the rate of IBTR with IORT was not non-inferior to WBI. Here are long-term results of the ELIOT trial. ELIOT was a single-center, randomized phase 3 trial of > 1300 women age 48-75 with unifocal breast cancer, size on ultrasound 2.5 cm or less, and a clinically negative axilla who were planning to undergo breast conservation surgery. They were randomized to receive either standard whole breast radiation (50 Gy in 25 fractions + 10 Gy in 5 fractions boost) or IORT (21 Gy in 1 fraction). Electron therapy was delivered using a mobile linear accelerator. The breast was reconstructed prior to IORT and beam energy was chosen based on tumor bed size and breast thickness. The cavity target was prescribed 21 Gy to the 90% isodose line in 1 fraction. After a median follow-up of > 12 years, the rate of IBRT was significantly higher with IORT (11%) compared to WBI (2%). The IBTR risk also separated over time with an absolute difference between arms of 3.7% at 5 years, 7% at 10 years, and 10.2% at 15 years. In addition, IORT was associated with higher rates of nodal failure and locoregional failure, but not distant failure. The difference in IBTR rate was maintained across most subgroups. There was no difference in overall survival.

TBL: Over 10+ years, the risk of breast tumor recurrence and nodal recurrence is significantly higher with IORT than whole breast RT, although there is no apparent difference in the risk of metastasis or death. | Orecchia, Lancet Oncol 2021