118P Should DIBH (deep inspiration breath-hold) be the standard of care in LBC (left breast cancer)?

Abstract

Radiotherapy is the most effective treatment to eradicate the residual locoregional disease after breast cancer surgery with significative survival improvements after 15 years post diagnostic. For women receiving left-breast radiotherapy (DIBH) is used to further mitigate mortality and morbidity due to late cardiac toxicity, with a demonstrated linear relationship with Mean Heart Dose (MHD). The risk increases 7.4% per Gy, starting within the first 5 years and continuing into the third decade after radiotherapy. The aim of this study was to evaluate the effect of DIBH irradiation on MHD, V16, V8, V4 and mean, maximum and D10% left anterior descending coronary artery (LADCA) dose. 75 patients with left breast cancer (LBC), after radical mastectomy or conservative surgery, that were able to maintain voluntary DIBH ≥ 20 seconds, were irradiated with this cardiac sparring approach. All patients received hypofractionated radiotherapy (total dose of 40.05Gy / 2.67Gy per fraction) with 58 receiving a concomitant boost (total dose of 48Gy / 3.2Gy per fraction) and 9 patients having axillary nodes irradiated. The target volume was delineated on CT in DIBH and Free Breathing (FB) according to the ESTRO consensus guideline and heart according to the CT-based atlas by Feng et al. Tangent-based intensity modulated radiation therapy (n: 71) or VMAT (n: 4) plans were developed for both datasets. Patient set-up and tracking in FB/DIBH was monitored by Surface Guided Radiation Therapy (VisionRT, London, UK), after daily validation by cone beam CT matching. DIBH reduces significantly MHD, V16, V8, V4 and mean, maximum and D10% LAD dose compared to FB (p = 0.001). This difference is irrespective of breast PTV volume (797±367.6 cm3) or boost PTV volume (75.3 ± 30.3cm3). DIBH average MHD was 1.20 Gy (0.87-1.62) and average LADCA Dmean of 4.95 Gy (2.79-9.14) with respectively in FB 3.18 Gy (2.47-4.26) and 20.20Gy (12.29.-25.40). DIBH in LBC does lead to a significant reduction in heart and LADCA doses by increasing the distance between target and heart. These reductions could contribute to increase cardiovascular health of LBC. These findings apply to all patients and further studies will indicate to which subgroups the benefits are more pronounced.