Intraoperative radiation therapy
Encyclopedia
Intraoperative radiation therapy is applying therapeutic
levels of radiation to a target area, such as a cancer tumor, while the area is exposed during surgery
.
is a technique developed since 1998 for treatment of the tumour bed after wide local excision (lumpectomy) of breast cancer. It has recently been shown to give results equivalent to several weeks of whole breast radiation therapy at 4 years, as published in the Lancet - Online First
technique.
Radiation therapy
Radiation therapy , radiation oncology, or radiotherapy , sometimes abbreviated to XRT or DXT, is the medical use of ionizing radiation, generally as part of cancer treatment to control malignant cells.Radiation therapy is commonly applied to the cancerous tumor because of its ability to control...
levels of radiation to a target area, such as a cancer tumor, while the area is exposed during surgery
Surgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
.
Applications
The goal of IORT is to improve local tumor control and survival rates for patients with different types of cancer. Targeted intraoperative radiotherapyTARGIT
TARGIT is a technique of giving radiotherapy to the tissues surrounding a cancer after its surgical removal. The technique was designed in 1998 at the University College London...
is a technique developed since 1998 for treatment of the tumour bed after wide local excision (lumpectomy) of breast cancer. It has recently been shown to give results equivalent to several weeks of whole breast radiation therapy at 4 years, as published in the Lancet - Online First
Rationale
The rationale for IORT is to deliver a high dose of radiation precisely to the targeted area with minimal exposure of surrounding tissues which are displaced or shielded during the IORT. Conventional radiation techniques such as external beam radiotherapy (EBRT) following surgical removal of the tumor have several drawbacks: The tumor bed where the highest dose should be applied is frequently missed due to the complex localization of the wound cavity even when modern radiotherapy planning is used. Additionally, the usual delay between the surgical removal of the tumor and EBRT may allow a repopulation of the tumor cells. These potentially harmful effects can be avoided by delivering the radiation more precisely to the targeted tissues leading to immediate sterilization of residual tumor cells. Another aspect is that wound fluid has a stimulating effect on tumor cells. IORT was found to inhibit the stimulating effects of wound fluid.Methods
IORT can both be performed with electron beams (IOERT) and X-rays. Modern IORT started in shielded operation rooms in which a linear accelerator was used to deliver the radiation. In recent years, miniaturised and mobile-linear accelerators have been developed which deliver a variable range of electron energies (from 3 to 12 MeV), e.g. the Mobetron (Intraop Medical Corporation, USA). Intrabeam, (Carl Zeiss, Germany) is a miniature and mobile X-ray source which emits low energy X-ray radiation (max. 50 kV) in isotropic distribution. Due to the higher ionization density caused by soft X-ray radiation in the tissue, the relative biological effectiveness (RBE) of low-energy X-rays on tumor cells is higher when compared to high-energy X-rays or gamma rays which are delivered by linear accelerators. The radiation which is produced by mobile radiation systems has a limited range. For this reason, conventional walls are regarded sufficient to stop the radiation scatter produced in the operating room and no extra measures for radiation protection are necessary. This makes IORT accessible for more hospitals.Clinical Applications
IORT was found to be useful and feasible in the multidisciplinary management of many solid tumors but further studies are needed to determine the benefit more precisely. Single-institution experiences have suggested a role of IORT e.g. in brain tumors and cerebral metastases, locally advanced and recurrent rectal cancer, skin cancer, retroperitoneal sarcoma, pancreatic cancer and selected gynaecologic and genitourinary malignancies. For local recurrences, irradiation with IORT is besides brachytherapy the only radiotherapeutic option if repeated EBRT is no longer possible. Generally, the normal tissue tolerance does not allow a second full-dose course of EBRT, even after years.IORT in Breast Cancer
The largest experience with IORT and the best evidence for its potentials exists in breast cancer where a substantial number of patients have already been treated using, for example, the TARGITTARGIT
TARGIT is a technique of giving radiotherapy to the tissues surrounding a cancer after its surgical removal. The technique was designed in 1998 at the University College London...
technique.
See also
- Intraoperative Electron Radiation Therapy (IOERT) IOERT
- Brachytherapy BrachytherapyBrachytherapyBrachytherapy , also known as internal radiotherapy, sealed source radiotherapy, curietherapy or endocurietherapy, is a form of radiotherapy where a radiation source is placed inside or next to the area requiring treatment...
- External beam radiotherapy (EBRT) EBRT