Using Breath Hold Technique Helps Radiotherapy Hit Treatment Targets

Respiratory movement during radiotherapy makes it difficult to hit the correct treatment target and this in turn can lead to an under-dose of radiation to the tumor, or a potentially toxic overdose to the surrounding healthy tissue. Getting this right is a major task for the radiotherapist, but new techniques are helping to deliver the correct dose to the appropriate place.

Dr. Amira Ziouèche, a radiotherapy specialist from the Centre Léon Bérard (Lyon, France), presented findings at the 31st conference of the European Society for Radiotherapy and Oncology (ESTRO 31), held May 2012 in Barcelona (Spain), that showed how the technique of deep inspiration breath hold (DIBH) can spare the heart when irradiating left-side breast cancer tumors. In a prospective study, undertaken while she was working with Dr. Alice Mege at the Institut Sainte Catherine (Avignon, France), she demonstrated that treating patients during DIBH, while they were holding their breath at between 60% to 80% of their maximum inspiratory (breathing-in) capacity, could spare their hearts and lungs from radiation without compromising the quality of their treatment.

“Unlike treatment under free breathing [FB], where the patient breathes normally, DIBH spares the heart by reducing its volume and movement in the field to be irradiated, and the lung expansion involved in holding breath leads to a decrease of relative lung volume which is irradiated,” Dr. Ziouèche explained. “In effect, we can largely eliminate the problem of respiratory movement by using this technique, which allows us to reduce the volume of the healthy organ irradiated around the target volume while improving treatment precision. This is particularly important in breast cancer cases, where the life expectancy of most patients is long.”

Dr. Ziouèche and colleagues gathered data on 31 patients treated with DIBH between October 2007 and June 2010 at the Institut Sainte Catherine. Each patient was her own case-control and underwent two CT scans, one in FB and the other in DIBH. The dose to healthy organs and targets was calculated based on these scans. Analysis showed that the heart mean dose decreased from 9 Gy in FB to 3.7 Gy in DIBH, and the maximum heart dose from 44.9 Gy to 24.7 Gy. The amount of radiation to the lung was also decreased with DIBH.

“This is the largest study to date of the use of DIBH in patients undergoing radiotherapy for breast cancer,” Dr. Ziouèche stated. “It is an important result for breast cancer patients, where it can spare the volume of heart and lungs that are irradiated. Commonly, the margins around the tumor to be treated are increased in order to take movement into account. But this involves treating a larger area, some of it unnecessarily. The use of DIBH avoids this problem. Although the DIBH procedure initially involves additional time and therefore cost, if this technique results as we believe it will, in a clinical benefit in terms of reducing cardiac and pulmonary sequelae in specific cases it could result in lower healthcare costs in the longer term. Currently, the DIBH technique is little used in breast cancer, and we need further studies of its clinical and economic benefits to demonstrate its value in breast radiation treatment. Once these studies are completed we would hope to see it in widespread use in the future, to the benefit of patients and healthcare systems alike.”

In another study presented to the conference, Gauthier Bouilhol, MSc, from the Centre Léon Bérard, Lyon (France), described how he and colleagues from Centre de Recherche en Acquisition et Traitement de l'Image pour la Santé (CREATIS; CNRS [Le Centre National de la Recherche Scientifique] UMR5220, Inserm U1044) have developed a model to adjust the method currently used for the calculation of safety margins to account for respiratory motion asymmetry during radiotherapy. “When a patient breathes during radiotherapy treatment,” Mr. Bouilhol explained, “the tumor may also move. The normal way of calculating the treatment margins to compensate for potential errors is based on a symmetrical model. But if tumor motion is asymmetric, the model is wrong.”

The researchers suggest a new model that takes into account the differences between the two margins involved in inhale and exhale motion. “We believe that our model, once clinically validated, will provide a more accurate assessment of the area which is required to be treated with radiation, and this will improve both safety and efficacy for patients,” Mr. Bouilhol said.

Related Links:
Centre Léon Bérard
Institut Sainte Catherine
Centre de Recherche en Acquisition et Traitement de l'Image pour la Santé