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Long-Term Outcomes With Electron Intraoperative Irradiation vs Whole-Breast Irradiation for Early Breast Cancer


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As reported in The Lancet Oncology by Orecchia et al, preplanned long-term follow-up in the Italian single-center phase III ELIOT trial continued to show a higher rate of ipsilateral breast tumor recurrence with electron intraoperative radiotherapy vs postoperative whole-breast irradiation, with no difference in overall survival being observed.

The initial study report showed an increased rate of ipsilateral breast tumor recurrence in the electron intraoperative radiotherapy group vs the whole-breast irradiation group after median follow-up of 5.8 years.

The long-term results of this trial confirmed the higher rate of ipsilateral breast tumor recurrence in the electron intraoperative radiotherapy group than in the whole-breast irradiation group, without any differences in overall survival. Electron intraoperative radiotherapy should be offered to selected patients at low risk of ipsilateral breast tumor recurrence.
— Orecchia et al

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Study Details

The open-label equivalence trial was performed at the European Institute of Oncology, Milan, and included 1,305 women with a clinical diagnosis of unicentric breast carcinoma with an ultrasound diameter not exceeding 25 mm and clinically negative axillary lymph nodes who were suitable for breast-conserving surgery. They were randomly assigned between November 2000 and December 2007 to receive electron intraoperative radiotherapy (n = 651) or whole-breast irradiation (n = 654). The electron intraoperative radiotherapy group received 21 Gy of intraoperative radiotherapy with electrons in a single dose to the tumor bed during surgery; the whole-breast irradiation group received postsurgical conventional fractionation with 50 Gy in 25 fractions, plus a 10-Gy boost.

Key Findings

After a median follow-up of 12.4 years (interquartile range = 9.7–14.7 years), 86 patients (7%) developed ipsilateral breast tumor recurrence, including 70 (11%) in the electron intraoperative radiotherapy group vs 16 (2%) in the whole-breast irradiation group; the difference corresponded to an absolute excess of 54 ipsilateral recurrences in the electron intraoperative radiotherapy group (hazard ratio [HR] = 4.62, 95% confidence interval [CI] = 2.68–7.95, P < .0001).

Ipsilateral breast tumor recurrence rates in the electron intraoperative radiotherapy group vs the whole-breast irradiation group were 4.2% (95% CI = 2.8%–5.9%) vs 0.5% (95% CI = 0.1%–1.3%) at 5 years, 8.1% (95% CI = 6.1%–10.3%) vs 1.1% (95% CI = 0.5%–2.2%) at 10 years, and 12.6% (95% CI = 9.8%–15.9%) vs 2.4% (95% CI = 1.4%–4.0%) at 15 years.

At final follow-up in March 2019, 193 women (15%) had died from any cause. No difference in overall survival was observed between the electron intraoperative radiotherapy group (98 deaths) vs the whole-breast irradiation group (95 deaths; HR = 1.03, 95% CI = 0.77–1.36, P = .85).

Overall survival rates in the electron intraoperative radiotherapy group vs the whole-breast irradiation group were 96.8% (95% CI = 95.1%–97.9%) vs 96.8% (95% CI = 95.1%–97.9%) at 5 years, 90.7% (95% CI = 88.2%–92.7%) vs 92.7% (95% CI = 90.4%–94.4%) at 10 years, and 83.4% (95% CI = 79.7%–86.4%) vs 82.4% (95% CI = 78.5%–85.6%) at 15 years.

The investigators concluded, “The long-term results of this trial confirmed the higher rate of ipsilateral breast tumor recurrence in the electron intraoperative radiotherapy group than in the whole-breast irradiation group, without any differences in overall survival. Electron intraoperative radiotherapy should be offered to selected patients at low risk of ipsilateral breast tumor recurrence.”

Roberto Orecchia, MD, of the IEO European Institute of Oncology IRCCS, Milan, is the corresponding author for The Lancet Oncology article.

Disclosure: The study was funded by the Italian Association for Cancer Research, Jacqueline Seroussi Memorial Foundation for Cancer Research, Umberto Veronesi Foundation, Italian Ministry of Health, and others. For full disclosures of the study authors, visit thelancet.com.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
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