Treatment of early-stage breast cancer using electron intraoperative radiation therapy (ELIOT) was found to increase the incidence of ipsilateral breast tumor recurrence (IBTR), according to the results of a phase 3 equivalence study published in The Lancet Oncology.
“Risk stratification of patients is necessary to select the optimal treatment method for individual patients; those with high risk features should be definitively excluded from intraoperative radiotherapy,” the authors wrote.
The prospective, open-label, single-center, randomized trial (ClinicalTrials.gov Identifier: NCT01849133) was conducted at the European Institute of Oncology in Italy to investigate the long-term outcomes of ELIOT after conserving surgery in early-stage breast cancer compared with whole breast irradiation (WBI). From November 2000 to December 2007, the study enrolled 1305 women who were randomly assigned either to the ELIOT group (651 patients) or the WBI group (654 patients) via a web-based system.
At baseline, 87 (7%) of the enrolled study participants were younger than 50 years of age, and 148 (11%) had a lobular or mixed lobular and ductal histology. Also included were women with large or poorly differentiated tumors, positive nodes, negative hormone receptor status, and a high proliferative index. The primary endpoint of the study was the IBTR, and the secondary endpoint was overall survival (OS) assessed at 5, 10, and 15 years of follow-up.
After a median follow-up of 12.4 years (interquartile range [IQR], 9.7-14.7), 86 (7%) of the patients developed IBTR. Of these, women in the ELIOT group had a remarkably higher incidence of IBTR (70/651 [11%] of patients) compared with those in the WBI group (16/654 [2%] of patients), with an absolute excess of 54 IBTRs in the ELIOT group (hazard ratio [HR], 4.62; 95% CI, 2.68-7.95; P <.0001). In the ELIOT group, the rate of IBTR at 5 years, 10 years, and 15 years was 4.2% (95% CI, 2.8-5.9), 8.1% (6.1-10.3), and 12.6% (9.8-15.9), respectively. In the WBI group, the rate of IBTR at 5 years, 10 years, and 15 years was 0.5% (95% CI, 0.1-1.3), 1.1% (0.5-2.2), and 2.4% (1.4-4.0), respectively.
Although the rate of local and regional recurrences among women with early-stage breast cancer was significantly higher after ELIOT than after WBI, there was no difference in the overall mortality, breast cancer mortality, and the development of distant metastases between the 2 groups (98 deaths in the ELIOT group vs 95 in the WBI group; HR, 1.03; 95% CI, 0.77-1.36; P =.85).
In the ELIOT group, the OS rate was 96.8% (95% CI, 95.1-97.9), 90.7% (88.2-92.7), and 83.4% (79.7-86.4) at 5, 10, and 15 years, respectively. In the WBI group, the OS rate was 96.8% (95.1-97.9), 92.7% (90.4-94.4), and 82.4% (78.5-85.6) at 5, 10, and 15 years, respectively.
Immunohistochemical tumor profiling, including a combination of measuring the protein expression of estrogen receptor, progesterone receptor, HER2, and Ki-67 along with the clinicopathological variables might help to stratify patients at very low, low, or higher risk of recurrence.
Orecchia R, Veronesi U, Maisonneuve P, et al. Intraoperative irradiation for early breast cancer (ELIOT): long-term recurrence and survival outcomes from a single-centre, randomised, phase 3 equivalence trial. Lancet Oncol. Published online April 9, 2021. doi:10.1016/ S1470-2045(21)00080-2