Abstract
A right-sided breast cancer patient (stage T1N0M0) was referred for post-surgical radiotherapy to minimize risk of local tumour recurrence. During the CT simulation and intensity-modulated radiotherapy planning process undertaken in free breathing, it was apparent that an unusually large volume of normal liver tissue (134 cc) was in the high-dose region of the tangential radiation field. This raised concern for risk of liver side effects and was considered suboptimal for this excellent prognosis patient. A deep inspiration breath-hold (DIBH) technique using three-dimensional (3D) surface monitoring-primarily developed and applied in left breast cancer to displace cardiac tissue from the target field-was investigated to determine potential benefit to optimize radiotherapy delivery. Resimulation of DIBH resulted in considerable displacement of the liver, reducing the volume of liver tissue in the target field by 63% (to 50 cc) and the mean liver dose by 46% (to 2.6 Gy). As the patient was deemed suitable for the DIBH technique, treatment was delivered according to the DIBH plan. A total of 40.05 Gy in 15 fractions was successfully delivered in the DIBH position using a technique that incorporated 3D body surface imaging with automated radiation beam hold-off when out of tolerance. Additional advantages were optimal set up without extensive immobilization and the elimination of respiratory motion. Acute mild skin erythema was the only side effect experienced-no liver sequalae were experienced by the patient up to 6 months after treatment. DIBH treatment may improve liver sparing in other similar right breast cancer patients.