A Retrospective Analysis of Lung Volume and Cardiac Dose in Left-Sided Whole Breast Radiotherapy

The purpose of this study was to assess the variability of lung volume and characterize its relationship with heart dose in women with left-sided breast cancer receiving whole breast radiotherapy.

Free-breathing (FB) computed tomography scans of female left-sided breast cancer patients were retrospectively reviewed. Dose and volume parameters for the lung, heart, and left anterior descending coronary artery were collected from the FB treatment plans of 47 patients treated in FB (PT_FB) and 41 patients who exceeded institutional heart dose limits (≥10 cc of heart receiving V50%) and required the breath-hold technique using the active breathing coordinator (ABC) device (PT_ABC). A two-tailed Student's t-test and Pearson's correlation test were performed for statistical analysis.

Volume of the heart and left anterior descending artery were similar between the groups (P = .102 and P = .548, respectively). Total left lung volume in FB state was significantly smaller for the PT_ABC group (996.9 cc; standard deviation, 253.1) when compared with the PT_FB group (1,207.8 cc standard deviation, 32; P < .001). Mean and maximum heart dose, heart V50%, V30 Gy, and V10 Gy decreased with increasing left lung volume for all patients (P < .001). There was an inverse relationship between left lung volume and mean heart dose (R = -0.586, P < .001).

Patients requiring ABC have smaller left lung volumes during FB state. Future study to assess lung volume in conjunction with other anatomic parameters in the development of an ABC screening tool is warranted.