Effects of lung tissue characterization in radiotherapy of breast cancer under deep inspiration breath hold when using Monte Carlo dosimetry

Introduction: The purpose of this study was to compare the radiation dose to organs at risk for deep-inspiration breath hold (DIBH) and free-breathing (FB) radiotherapy in patients with lef-sided breast cancer undergoing adjuvant radiotherapy after partial mastectomy. Methods: One hundred patients with left-sided breast cancer underwent DIBH and FB planning computed tomography scans, and the 2 techniques were compared. Dose-volume histograms were analyzed for heart, left anterior descending coronary artery (LAD), and left lung. Results: Radiation dose to heart, LAD, and left lung was significantly lower for DIBH than for free breathing plans. The median mean heart dose for DIBH technique in comparison with FB was 1.21 Gy, and 3.22 Gy respectively; for LAD, 4.67 versus 24.71 Gy; and for left lung 8.32 Gy versus 9.99 Gy. Conclusion: DIBH is an effective technique to reduce cardiac and lung radiation exposure.

Objective: To prospectively analyze the feasibility of an algorithm for patient preparation, treatment planning and selection for deep inspiration breath-hold (DIBH) treatment of left-sided breast cancer. Methods: From 02/2017 to 07/2019, 135 patients with left-sided breast cancer were selected and prepared for radiotherapy in DIBH. 99 received radiotherapy for the breast alone and 36 for the breast including the lymphatic drainage (RNI). Treatment plans DIBH and free breathing (FB) were calculated. Dosimetrical analyses were performed and criteria were defined to assess whether a patient would dosimetrically profit from DIBH. Results: Of the 135 patients, 97 received a DIBH planning CT and 72 were selected for treatment in DIBH according to predefined criteria. When using DIBH there was a mean reduction of the DmeanHeart of 2.8 Gy and DmeanLAD of 4.2 Gy. seven patients did not benefit from DIBH regarding DmeanHeart, 23 regarding DmeanLAD. For the left lung the V20Gy was reduced by 4.9%, the V30Gy by 2.7% with 15 and 29 patients not benefitting from DIBH, respectively. In the 25 patients treated in FB, the benefit of DIBH would have been lower than for patients treated with DIBH (ΔDmeanHeart0.7 Gy vs 3.4 Gy). Conclusion: Dosimetrically, DIBH is no “one fits all” approach. However, there is a statistically significant benefit when looking at a larger patient population. DIBH should be used for treatment of left-sided breast cancer in patients fit for DIBH. Advances in knowledge: This analysis offers a well-designed dosimetrical analysis in patients treated with DIBH radiotherapy in an “every day” cohort.