Introduction of moderate deep inspiration breath hold for radiation therapy of left breast: Initial experience of a regional cancer center.

PURPOSE:Practical aspects of introducing moderate deep inspiration breath hold (mDIBH) for treatment of left breast cancer in a regional cancer program in terms of workflow and treatment delivery requirements are described. Differences in heart and lung doses between free breathing (FB) and mDIBH plans are presented as well as heart position reproducibility and resulting dosimetric impact using cone beam computed tomography (CBCT). METHODS AND MATERIALS:A mDIBH process was established. Therapists observed duration and quantity of breath holds required for setup, imaging, and beam delivery during treatment. Treatment plans were generated on the FB and mDIBH CT datasets allowing comparison of heart and lung dose-volume data for 50 patients. Five consecutive CBCT images were used to measure the distance between the heart and chest wall for 5 patients. Estimates of dose to the translated heart were then made with the treatment planning system. RESULTS:When compared with FB delivery, mDIBH treatment time for tangents and boosts increased by 5 minutes, while 3- or 4-field techniques increased by 10 minutes. Differences in heart dose D10 cc, mean, V30 and V10 were statistically significant between the FB and mDIBH tangents and 3- or 4-field treatment plans. Statistically significant differences in V20, V10, V5, and mean lung doses were observed for 3- and 4-field FB and mDIBH plans. Differences between lung V5 dose metrics for FB and mDIBH 2-field plans were statistically significant. Interfraction mean translations in heart position coronally ranged from -6.2 to 2.6 mm and resulted in non-negligible increases in the heart dose. CONCLUSIONS:Moderate deep inspiration breath hold has been successfully implemented in our regional cancer center for treatment of left breast cancer and is now a standard practice. This change in practice from FB to mDIBH treatment has not impacted our ability to meet provincial guidelines for patient throughput.