Intraoperative radiation therapy (IORT) is applying therapeutic levels of radiation to a target area, such as a cancer tumor, while the area is exposed during surgery. The goal of IORT is to improve local tumor control and survival rates for patients with different types of cancer.
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.
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 targeted intra-operative radiotherapy (TARGIT) technique.
On 11 November 2013 the 5-year results of local recurrence and overall survival from the TARGIT-A trial of TARGIT IORT for breast cancer were published in the Lancet. 3451 patients from 33 centres in 11 countries participated in the trial. The analysis of the data found that
- with longer follow up, the results are stable,
- local recurrence in the conserved breast with TARGIT concurrent with lumpectomy is similar to whole breast radiotherapy,
- breast cancer mortality is similar with TARGIT and EBRT, and
- deaths from causes other than breast cancer- cardiovascular and other cancers – are significantly reduced.
The conclusion was that TARGIT concurrent with lumpectomy within a risk-adapted approach should be considered as an option for eligible patients with breast cancer carefully selected as per the TARGIT-A trial protocol, as an alternative to postoperative EBRT. The results of TARGIT TARGIT IORT for breast cancer are discussed in a podcast of the TARGIT-A and ELIOT trials on the Lancet website. (full TARGIT IORT paper).
Deep inspiration breath-hold
Deep inspiration breath-hold (DIBH) is a method of delivering radiotherapy while limiting radiation exposure to the heart and lungs. It is used primarily for treating left-sided breast cancer. The technique involves a patient holding their breath during treatment. There are two basic methods of performing DIBH: free-breathing breath-hold and spirometry-monitored deep inspiration breath hold.