Abstract
Intraoperative radiotherapy (IORT) is a technique that involves precise delivery of a large dose of ionising radiation to the tumour or tumour bed during surgery. Direct visualisation of the tumour bed and ability to space out the normal tissues from the tumour bed allows maximisation of the dose to the tumour while minimising the dose to normal tissues. This results in an improved therapeutic ratio with IORT. Although it was introduced in the 1960s, it has seen a resurgence of popularity with the introduction of self-shielding mobile linear accelerators and low-kV IORT devices, which by eliminating the logistical issues of transport of the patient during surgery for radiotherapy or building a shielded operating room, has enabled its wider use in the community.Electrons, low-kV X-rays and HDR brachytherapy are all different methods of IORT in current clinical use. Each method has its own unique set of advantages and disadvantages, its own set of indications where one may be better suited than the other, and each requires a specific kind of expertise.IORT has demonstrated its efficacy in a wide variety of intra-abdominal tumours, recurrent colorectal cancers, recurrent gynaecological cancers, and soft-tissue tumours. Recently, it has emerged as an attractive treatment option for selected, early-stage breast cancer, owing to the ability to complete the entire course of radiotherapy during surgery. IORT has been used in a multitude of roles across these sites, for dose escalation (retroperitoneal sarcoma), EBRT dose de-escalation (paediatric tumours), as sole radiation modality (early breast cancers) and as a re-irradiation modality (recurrent rectal and gynaecological cancers).This article aims to provide a review of the rationale, techniques, and outcomes for IORT across different sites relevant to current clinical practice.
Highlights
Introduction of electronIntraoperative radiation therapy (IORT) (IOERT) marked the beginning of the IORT era in the early 1960s [3, 4]
IORT has been used in a multitude of roles across these sites, for dose escalation, external beam radiotherapy (EBRT) dose de-escalation, as sole radiation modality in early-breast cancers and as a Re-irradiation modality in recurrent cancers
Utility of IORT has been tested in the setting of a randomised control trial in early breast, retroperitoneum, gastric and colorectal cancers, the results of which support the use of IORT as a management option in these settings
Summary
Intraoperative radiation therapy (IORT) constitutes delivery of radiation to the tumour/tumour bed while the area is exposed during surgery. IORT is capable of delivering high doses of radiation, precisely to the tumour bed with minimal exposure to the surrounding healthy tissues. Surgery is followed by EBRT in most solid tumours for the elimination of any microscopic residual disease and reducing the risk of local recurrence. Difficulty in tumour bed localisation or use of larger margins, which may increase normal tissue morbidity. Most solid tumours exhibit a dose–response relationship, the likelihood of local control improving with increasing dose; there are limitations to the doses that can be delivered even with conformal EBRT techniques due to the presence of dose-limiting structures adjacent to the tumour/tumour bed. In the setting of gross residual disease, doses with EBRT may never be sufficient to achieve adequate local control without causing significant morbidity Most centres use it in combination with EBRT, as it seems to provide the best therapeutic ratio (decreased risk of late normal tissue damage due to the use of fractionation for some part of the dose)
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