Prospective assessment of deep inspiration breath hold to prevent radiation-associated cardiac perfusion defects in patients with left-sided breast cancer.

Abstract

41 Background: Radiation therapy (RT) for left-sided breast cancer can cause regional cardiac perfusion abnormalities in nearly half of patients at 6 months post-RT. While the significance of these perfusion abnormalities remains unclear, RT is a well-accepted risk factor for heart disease. We herein report the results of a single-arm prospective clinical study to assess deep inspiratory breath hold (DIBH; using AlignRT) as a means to prevent the development of perfusion abnormalities in patients with left-sided breast cancer. Methods: Patients about to receive left-sided tangential RT had a pre-RT cardiocentric single photon emission computed tomography with CT based attenuation correction (IQ SPECT-CT) rest-cardiac gated perfusion scan (to assure a normal baseline). DIBH and conformal blocking was used to assure that the heart was excluded from the primary RT beam. Doses to the heart were computed. At 6-months post-RT, the SPECT-CT was repeated. The perfusion and motion images were assessed qualitatively by a nuclear medicine physician. Results: Twenty-four patients have been enrolled. Four were not evaluable (e.g. due to an abnormal pre-RT SPECT scan); one has been lost to follow-up. All patients received tangential radiation to the breast/chest wall (typical doses 200 cGy x 25 or 267 cGy x 16); five also received regional nodal RT as well; and 18/19 received a tumor bed boost. The mean heart dose ranged from 42-160cGy for all 19 patients (mean of the means = 78 cGy). Of the 19 potentially evaluable patients, post-RT SPECTs have been obtained in ten. All ten have a normal post-RT SPECT scan; and/or no change from pre-RT scan. Conclusions: In patients receiving tangential RT for left-sided breast cancer, cardiac avoidance with DIBH (e.g. with AlignRT) and conformal field shaping, appears to be able to prevent the development of RT-associated cardiac perfusion abnormalities. The mean dosages to the heart are quite low. Updated information on the remaining patients will be presented. Funded in part by VisionRT. Clinical trial information: NCT01849614.