8.3.4 Radiotherapy for Respiratory Adaptation to P...
Although modern radiotherapy is used，there is no consistent conclusion whether postoperative radiotherapy for breast cancer will increase the risk of cardiovascular death in breast cancer.Marks found that the incidence of myocardial perfusion defect was 42%2 years after radiotherapy，which was related to the volume of cardiac irradiation［15］.Therefore，the volume of cardiac irradiation should be reduced as much as possible in order to reduce cardiac toxicity.IMRT can reduce the exposure volume of the heart.But for some patients whose hearts are close to the chest wall（heart anatomy is challenging），even IMRT can't avoid part of the heart（especially the left anterior descending branch of the ventricle and coronary artery）being exposed to a high dose of radiation.Breath-holding（DIBH）can inflate the lung after deep breath inhalation，and the heart moves backward and below，leaving the chest wall（Fig.8-11）.In recent years，physical dosimetry studies have shown that for patients with left breast cancer，breath-holding（DIBH）can reduce the volume of the heart in the irradiated field compared with free breathing，and DIBH can significantly increase the likelihood of death from radiation-induced heart disease（0.1%and 4.8%）［16］.Compared with free breathing，both free breath gated radiotherapy（end inspiratory gated）and DIBH can reduce the volume of cardiac irradiation.DBH technique is superior to end inspiratory gated therapy in protecting the heart..
Remouchamps reported the clinical experience of using ABC device to moderate inspiratory end breath holding（mDIBH）and conventional wedged plate tangent field in the treatment of 5 patients with left breast cancer.All patients could tolerate the treatment very well.Each treatment required 4 times and 6 times to hold breath，the median breath holding time was 22 seconds，and the median treatmenttime was 18 minutes.The positioning error in all directions is in 2.1～3.2mm［17］.DIBH is a promising radiotherapy technique for respiratory adaptation to protect the heart in patients with left breast cancer who are challenging cardiac anatomy.(https://www.daowen.com)
Fig.8-11 Changes in cardiac position of CT scan in free breathing state and DIBH（blue is the left whole breast CT，red shown on CT in free breathing state is the whole heart in DBH state）