Radiation therapy uses high-energy rays to destroy cancer cells. For breast cancer, it is often used after surgery, such as breast conservation, mastectomy, or reconstruction. The left breast is located over the heart and close to the left pleura. Radiation therapy to the left chest carries a risk of radiation exposure to the heart, pleura, and lungs, leading to late complications like coronary artery disease and pneumonia. Radiation exposure exceeding safe limits can cause pulmonary fibrosis and permanent respiratory dysfunction.

For patients undergoing radiation therapy for left breast cancer, doctors often use the deep inspiration breath hold (DIBH) technique. When the patient takes a deep breath, the chest expands, moving the breast forward and pushing the heart downwards and backward. This creates space, moving the heart and most of the lung tissue out of the radiation field. The patient then holds their breath for about 20 seconds. Radiation delivery occurs during this 20-second breath hold to reduce the radiation dose to the heart, pleura, and lungs. During each session, patients must take deep breaths and hold them several times.

Doctor Loc advises a patient. *Illustration: Tam Anh General Hospital*

Throughout the radiation therapy, a 3D optical camera scans the patient's chest surface in real time. The scanner identifies thousands of coordinate points on the skin, ensuring the patient's deep breath hold achieves the correct chest volume as determined during the simulation CT scan. If the patient becomes fatigued, exhales, or moves incorrectly by only 1-2 millimeters, the system automatically cuts off the radiation beam immediately. This prevents the risk of radiation being misdirected to the heart due to positioning errors or unintended patient movement. The DIBH technique can reduce the average radiation dose to the heart by 50-70% compared to free breathing.

For radiation therapy of thoracic and abdominal cancers, such as lung or liver cancer, where tumors can move with breathing, doctors also use the DIBH technique. This helps control tumor movement, ensuring accurate and safe treatment.

Patients should choose a hospital equipped with a linear accelerator system capable of performing all radiation therapy techniques, including intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). Such systems can adjust the shape and intensity of thousands of small radiation beams during delivery. This precisely concentrates the maximum dose on breast tissue while minimizing the dose to surrounding healthy tissue.

Doctor of First Degree Specialist Nguyen Huy Loc

Department of Radiation Therapy, Oncology Center

Tam Anh General Hospital HCMC