Reduction of cardiac volume in left-breast treatment fields by respiratorymaneuvers: A CT study

Purpose: A previous study of healthy female volunteers suggested that deep inspiratory breath holding can reduce the cardiac volume in the treatment p ortals for left-breast cancer treatment. The reduction of irradiated cardia c volume may be important considering the reported late cardiac morbidity a nd mortality and the frequent coexistent use of potentially cardiotoxic che motherapy in breast cancer patients. In the present study, we evaluated the heart volume in the fields and, thus, the true benefit of this respiratory maneuver in breast cancer patients undergoing CT simulation, Materials and Methods: Fifteen patients (median age, 53) were studied. For each patient, CT scans were performed both when the patient breathed normal ly (quiet respiration) and when the patient held her breath after a deep in spiration. Tangential fields were planned using the same medial, lateral, s uperior, and inferior borders on skin for the normal breathing and the brea th-holding configurations. The cardiac and left-lung volumes within the tan gential fields were calculated for both breathing configurations. Multiple scan series were performed for the breath-holding configuration to provide a more accurate delineation of the cardiac tissue and to study the reproduc ibility of the patient's position between different cycles of deep inspirat ion. Results: None of the patients had difficulty holding her breath for 20 s. T he cardiac volume in the field was reduced (-86 +/- 24%; p < 0.001) when pa tients held their breath after a deep inspiration compared to when breathin g normally. For 7 patients (47%), deep inspiration moved the heart complete ly out of the radiation fields. The expansion of the lung tissue due to dee p inspiration also increased the absolute lung volume in the tangential fie lds (183 cm(3) vs 97 cm(3), p < 0.001). However, the fractional volume of t he left lung in the field was essentially unchanged. For all but 1 patient, the maximum difference between the external body contours from different b reath holding cycles was 5 mm and occurred at the lateral aspect of the bre ast. At the medial aspect, as indicated by the position of the midline mark er, the variations were well within the currently accepted tolerance for pa tient positioning during tangential treatment. Conclusions: Deep-inspiration breath holding substantially reduces cardiac volume in the tangential fields for left-sided breast cancer treatment. The variation between patient positions at different cycles of breath holding was found to be reasonably small, Therefore, it appears feasible to reduce cardiac radiation by treating patients with intratreatment minifractions la sting 10-15 s while patients hold their breath. (C) 2000 Elsevier Science I nc.