ESTRO 2025 - Abstract Book

S483

Clinical - Breast

ESTRO 2025

1 Radiation Oncology, Netaji Subhas Chandra Bose Cancer Hospital, Kolkata, India. 2 Medical Physics, Netaji Subhas Chandra Bose Cancer Hospital, Kolkata, India

Purpose/Objective: Adjuvant external beam radiotherapy is an integral component in the treatment of left sided breast cancer, but alongwith delivery of radiation dose to the target volume, it also leads to incidental irradiation of surrounding critical organs such as the heart, the lungs, the left anterior descending artery(LAD) etc. This may lead to pulmonary or cardiovascular toxicities. The purpose of this study was to assess the potential benefit of voluntary deep inspiration breath hold technique over free breathing technique for CT simulation in patients of post-operative left sided breast cancer. Material/Methods: 15 patients of post-operative left-sided breast cancer advised for adjuvant radiation therapy were enrolled in this study. Each patient was coached and underwent two successive computed tomography simulations, based on free breathing(FB) and deep inspiration breath hold(DIBH) techniques respectively. Following target delineation on both CT scans, two treatment plans were generated for each patient( FB and DIBH), using Monaco treatment planning system. The two treatment plans were further normalized in terms of equivalent PTV(Planning Target Volume) coverage when a dose of 40Gy was delivered in 15 fractions. Dose volume histogram(DVH) parameters were then assessed and compared between both plans. Results: Mean dose to heart(Dmean) was significantly lower with DIBH(3.14 ± 1.02) as compared to FB plans(4.5 ± 1.2), p < 0.001. Also volumes receiving 5Gy, 10Gy, 25Gy were significantly lower with DIBH compared to FB plans. V25 was less than 10% in both plans for all patients(0.85 ± 1.3 in DIBH vs 2.56 ± 2.4 in FB, p = 0.01). Heart Dmax was also significantly lower with DIBH versus FB plans. Volume of heart irradiated did not vary significantly between both techniques. Mean dose to LAD (Dmean) was significantly lower with DIBH(7.4 ± 3.6) as compared to FB(12.8 ± 5.4), p < 0.001 . Maximum dose to LAD (Dmax) was also significantly lower with DIBH(21.5 ± 10.4) versus FB(31.23 ± 8.77), p = 0.007. Mean dose to ipsilateral lung and volumes receiving 5Gy, 10Gy, 20Gy did not vary significantly between both techniques. Mean dose to contralateral breast also did not vary between both techniques. Conclusion: Voluntary deep inspiration breath hold technique leads to significant reduction in dose to cardiac structures, namely heart and left anterior descending artery, as compared to free breathing technique, thereby decreasing the risk of radiation induced cardiovascular toxicity, in left-sided breast cancer patients undergoing adjuvant hypofractionated radiotherapy.

Keywords: Deep Inspiration Breath Hold, Free breathing

References: 1. Lai, J. et al. (2019) ‘Meta-analysis of Deep Inspiration Breath Hold (DIBH) versus Free Breathing (FB) in postoperative radiotherapy for left-side breast cancer’, Breast Cancer , 27(2), pp. 299–307. doi:10.1007/s12282-019 01023-9. 2. Aznar, M.C. et al. (2023) ‘Estro-ACROP guideline: Recommendations on implementation of breath-hold techniques in radiotherapy’, Radiotherapy and Oncology , 185, p. 109734. doi:10.1016/j.radonc.2023.109734.