The impact of semilateral decubitus position on the dose-volume parameters of the heart and lung for left sided breast cancer patients: A comparative dosimetric study

Abstract

PurposeWhen treating breast cancer with radiation therapy, the impact of treatment position on heart and lung dose-volume parameters (DVPs) is largely dependent on the maximal heart distance (MHD) and central lung distance (CLD). We evaluate how much heart and lung sparing can be achieved using the semilateral decubitus (SLD) position without and with breath hold compared with the standard supine position for left-sided breast cancer patients. A secondary aim was to investigate the impact of MHD and CLD on heart and lung DVPs. Methods and materialsThirty-five left-sided breast cancer patients were simulated in supine, free breathing SLD, and SLD with breath hold positions. A dosimetry plan was developed for each of these and 3 plans were compared for target coverage and organs at risk sparing. A correlation between CLD, MHD, and planning target volume, and heart and ipsilateral lung DVPs was tested. ResultsSLD breath hold position showed a significant reduction in percentage of heart receiving ≥5 Gy (V5Gy), V10Gy, V25Gy, V30Gy, mean dose and maximum dose (P < .001), ipsilateral lung V20Gy, and mean dose compared with supine (P < 001) and free breathing SLD (P = .003 and .006). There was also a significant reduction in the heart DVPs (P < .001) and ipsilateral lung DVPs (P < .001 and .007) with free breathing SLD compared with the supine position. SLD with or without breath hold were associated with significant reduction in MLD (P < .001) and CLD (P = .030 and .003) compared with the supine position. ConclusionTreatment plans for patients in the SLD position with or without breath hold for left-sided breast cancer patients demonstrated a superior heart and lung sparing compared with the supine position due to significant reduction in MHD and CLD. MHD and CLD are important simulation factors that affect the heart and lung DVP.