Biological Indices Evaluation of Various Treatment Techniques for Left-Sided Breast Treatment

Purpose: To compare dose to organs at risk (OARs) and biological evaluation using normal tissue complication probability (NTCP) for left-sided breast radiation therapy in 4 techniques: supine free breathing (SFB), supine deep inspiration breath hold (SDIBH), prone free breathing (PFB), and prone deep inspiration breath hold (PDIBH). Methods and Materials: Twenty-five patients with left-sided breast cancer suitable for this study underwent a computed tomography scan using SFB, SDIBH, PFB, and PDIBH. One radiation oncologist contoured the planning target volume and OAR (cardiac components). Dose-volume histograms and NTCPs for the heart, left ventricle (LV), left anterior descending artery (LAD), and left lung were calculated for all 4 techniques. Results: The mean heart dose in PDIBH is 0.77 Gy, which is statistically significantly lower than in SFB (1.88 Gy, P < .0001), SDIBH (0.97 Gy, P < .001), and PFB (0.85 Gy, P < .001). The mean left lung dose is 0.69 Gy in PFB and 0.88 Gy in PDIBH. PFB and PDIBH have statistically significantly lower doses compared with SFB (6.09 Gy, P < .0001) and SDIBH (5.41 Gy, P < .0001). The mean NTCP in SFB for the heart, LV, and LAD is 0.27%, 0.62%, and 4.23%, respectively, and it is negligible for other techniques. Conclusions: We found that PDIBH had a dosimetrically lower mean dose for the heart and LV compared with the other 3 techniques. In addition, SDIBH, PFB and PDIBH had statistically significantly lower NTCP for the heart, LV, and LAD compared with SFB. NTCP for the left lung was statistically significantly lower for prone techniques compared with supine techniques. Therefore we concluded that, compared with SDIBH, PDIBH provides the added benefit of sparing the heart while keeping the benefit of sparing the lung as in the prone technique. (C) 2019 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.