Intraoperative radiotherapy: review of techniques and results

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.

Intraoperative radiotherapy as an immediate adjuvant treatment of rectal cancer due to limited access to external-beam radiotherapy

“…During this period, residual tumor cells may be able to re-grow and/or migrate and on, the long run, cause local relapses. In this regard, IORT offers the advantage of instantaneous "sterilization" of the tumor bed, which was proven to be highly efficient in a wide variety of intra-abdominal tumours, recurrent colorectal cancers, recurrent gynaecological cancers, and soft-tissue tumours breast cancer, brain tumors and soft-tissue sarcoma [17][18][19][20]. A number of mono-institutional trials demonstrated improved local control of rectal cancer after IORT even in the era of neoadjuvant therapy [10], whereas specifically patients with microscopically-involved circumferential resection margins (CRM) may benefit most [9,[21][22][23].…”

Local Cancer Recurrence: The Realities, Challenges, and Opportunities for New Therapies

“…Although 2 randomized trials revealed no LRR or OS benefit with the addition of IORT, a pooled retrospective analysis of over 600 patients reported that IORT significantly reduced LRR rates in patients who underwent margin‐positive resection . Complication rates with IORT ranged from 5% to 60%, including wound complications in up to 40% of patients and gastrointestinal fistulae and ureteral injury in 2% to 12% …”

“…22 Complication rates with IORT ranged from 5% to 60%, including wound complications in up to 40% of patients and gastrointestinal fistulae and ureteral injury in 2% to 12%. 23 Despite the notable advances in surgical and adjuvant therapy over the past few decades, LRR rates for rectal cancers remain between 4% and 8%, and the more extensive surgery and adjuvant therapies all come with increased patient morbidity. Without treatment, patients with LRR experience a shortened life expectancy and often a poor quality of life.…”

Future Directions of Intraoperative Radiation Therapy: A Brief Review

“…IORT quickly became adopted worldwide despite the technical challenges ( 2 , 7 – 10 ) but became less used once IR equipment manufacturers ceased engaging in customized instrument changes. A recent resurgence of this treatment modality can probably be credited to the development of new types of IORT dedicated radiation devices such as mobile linear accelerators ( 11 ) and specially designed applicators for positioning of high activity radioactive sources ( 12 ). Thus, although current medical device regulations prevent in-house development of IORT accelerators—a problem that slowed this field until recently, the availability of commercial devices obviated this necessity.…”