Highlights
- •IOERT-Boost should primarily be considered in higher risk patients.
- •Full dose IOERT is one feasible APBI technique for patients with low-risk criteria.
- •For both concepts acute and late toxicities are mild.
- •IOERT does minimally impair cosmetic outcome.
- •Dose prescription and technical prerequisites are well established and described.
Abstract
The aim of this review is to provide a comprehensive overview of the role of intraoperative
radiation therapy with electrons (IOERT) in breast conserving therapy (BCT), both
as partial breast irradiation (PBI) as well as anticipated boost (“IOERT-Boost”).
For both applications, the criteria for patient selection, technical details/requirements,
physical aspects and outcome data are presented.
IOERT as PBI
The largest evidence comes from Italian studies, especially the ELIOT randomized trial.
Investigators showed that the rate of in-breast relapses (IBR) in the IOERT group
was significantly greater than with whole breast irradiation (WBI), even when within
the pre-specified equivalence margin. Tumour sizes >2 cm, involved axillary nodes,
Grade 3 and triple negative molecular subtypes emerged as statistically significant
predictors of IBR. For patients at low risk for in-breast recurrence (ASTRO/ESTRO
recommendations), full dose IOERT was isoeffective with standard WBI. Hence, several
national guidelines now include this treatment strategy as one of the standard techniques
for PBI in carefully selected patients.
IOERT Boost
The largest evidence for boost IOERT preceding WBI comes from pooled analyses performed
by the European Group of the International Society of Intraoperative Radiation Therapy
(ISIORT Europe), where single boost doses (mostly around 10 Gy) preceded whole-breast
irradiation (WBI) with 50 Gy (conventional fractionation). At median follow-up periods
up to ten years, local recurrence rates around 1% were observed for low risk tumours.
Higher local relapse rates were described for grade 3 tumours, triple negative breast
cancer as well as for patients treated after primary systemic therapy for locally
advanced tumours. Even in this settings, long-term (>5y) local tumour control rates
beyond 95% were achieved. These encouraging results are interpreted as being attributable
to utmost precision in dose delivery (by avoiding a “geographic and/or temporal miss”),
and the possible radiobiological superiority of a single high dose fraction, compared
to the conventionally fractionated boost.
IOERT also showed favourable results in terms of cosmetic outcome, assumedly thanks
to the small treated volumes combined with complete skin sparing.
Keywords
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Article info
Publication history
Published online: May 12, 2020
Accepted:
April 30,
2020
Received:
April 30,
2020
Identification
Copyright
© 2020 Elsevier B.V. All rights reserved.
