ESTRO 37 Abstract book

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ESTRO 37

dose received by all volumes examined, D10%- D100% inclusive, with dose reductions recorded ranging from 56.9%-27.4% respectively. The maximum LADCA dose, Dmax was reduced by 47.8% (DIBH mean=15.56Gy, SD=10.62Gy vs. FB mean=29.82Gy, SD=10.05Gy, p<0.000) and Mean LADCA Dose, Dmean by 52% (DIBH mean=5.23Gy, SD=1.94Gy vs. FB mean=10.88Gy, SD=3.95Gy p<0.000) when treated using DIBH over FB. Amplitude depths were not correlated with dose reductions, however, a DIBH depth proved superior to free breathing regardless if it was high, or low amplitude. Conclusion: DIBH treatment resulted in dose sparing for the heart and LADCA compared to FB treatment. This occurred simultaneously without increased dose to the combined or ipsi-lateral lung. Amplitude depths were not correlated with dose reduction hence cannot be used as indicators to achieve increased dose sparing effect. Further research and long term follow up is required to evaluate the clinical effect DIBH has in reducing long term cardiac/pulmonary complications and increasing patients’ overall mortality. SP-0562 Follow-up heart dose reduction. Where do we stand? M. Mast 1 , H. Struikmans 2 1 Haaglanden Medical Centre Location Westeinde Hospi, Radiation therapy DepartmentPostbus 411- 2260 LeidschendamROOM A2.003, Den Haag, The Netherlands 2 Haaglanden Medical Centre Antoniushove, Radiation therapy Department, Leidschendam, The Netherlands Abstract text Worldwide the highest rates of breast cancer are found in Western Europe [1]. Ferley et al. published the European figures, 464.000 new cases were diagnosed in 2012 [2]. Radiation therapy is often part of the treatment after breast conserving surgery, as became apparent from the EBCTCG data that the local recurrences were decreased by 2/3 in the group of patients receiving radiotherapy [3]. In the past decade it became apparent that after several years serious side effects might occur. Associations of RIHD with (mean) cardiac dose levels were described. In 2013 Darby et al. reported that rates of major coronary events increased with 7.4% per Gray and were proportional to the mean dose to the heart. It was shown that radiation induced heart diseases (RIHD) occur earlier than previously anticipated (< 5 years). Furthermore, they could not find a threshold dose [4]. This was confirmed in a study of van den Boogaard et al. Also it appeared that the left ventricular dose was a better predictor for risk on acute coronary events (ACE) [5] Apart from this, interactions with specific cytotoxic agents may lead to more heart damage. Rehammar et al. found the largest increases risk of heart disease in women who also received anthracycline-containing chemotherapy [6]. Finally, several studies investigate the risk factors for heart disease as well. Wethal et al. found that the irradiated arteries are characterized by widespread atherosclerotic lesions in lymphoma survivors [7]. The amount of Coronary Artery Calcium (CAC), is a reliable predictor of ACE in the general population [8,9]. And recently Roos et al. found that high pre-treatment CAC appears to be associated with ACE in breast cancer patients treated with postoperative radiotherapy [10]. Apart from the increasing awareness of these side effects, methods were found to decrease the dose in the heart and heart vessels. Using a breath-hold technique in patients with left-sided breast cancer is one of them [11]. In our department we found a less pronounced increase of CT-based CAC scores when using a breath- hold technique [12]. In this era of highly sophisticated technical improvements individualization of the cancer

treatment will bring us a step forward aiming at a longer survival and a better quality of life. 1. https://breast.cancerresearch/breast-cancer-facts- and-figures/ 2. Ferley et al. European Journal of Cancer 2013;49:1374 2005;365:1687 4. Darby et al. N Engl J Med 2013;368:987 5. Van den Boogaard et al. J Clin Oncol 2017;35:1171 6. Rehammar et al. Radiother Oncol 2017;123:299 7. Whetal et al. Radiother Oncol 2014;110:448 8. Greenland et al. Circulation 2007; 115:402 9. Oudkerk et al. Eur Radiol 18:2785–2807 10. Roos et al. Radiother Oncol 2017 [Epub ahead of print] 11. Mast et al. Radiother Oncol 108:248 12. Mast et al. Strahlenther Onkol. 2016;192:696 SP-0563 Prone whole-breast irradiation: are the benefits overshadowed by the challenges? L. Veldeman 1 1 University Hospital Ghent, Department of Radiation Oncology, Gent, Belgium Abstract text From an anatomical point of view, the prone position has clear benefits over the supine position for whole-breast irradiation. First, the breast falls away from the heart and lung by gravity, reducing the dose to these organs. Second, the typical breast shape in prone position improves dose homogeneity compared to supine position, especially in large breasted patients. Despite these advantages, only few radiotherapy departments worldwide use the prone position in clinical practice. The reasons for this are variable. One of the most important drawbacks of the prone position is the complex setup procedure which is more time-consuming and less reproducible than for the supine position. Another drawback is the more challenging target volume delineation because the anatomy is clearly different. Long-term randomized data on the efficacy of prone whole-breast irradiation are not available and sceptics fear that local control or overall survival data might be compromised. In this session, the benefits and challenges of prone breast irradiation are discussed including setup reproducibility, patient comfort, heart sparing and lymph node irradiation. 3. EBCTC Group. Lancet PV-0564 Predicting Genitourinary Toxicity by Machine Learning on Genome-Wide Single Nucleotide Polymorphisms S. Lee 1 , J. Oh 1 , S. Kerns 2 , B. Rosenstein 3 , H. Ostrer 4 , J. Deasy 1 1 Memorial Sloan Kettering Cancer Center, Department of Medical Physics, New York, USA 2 University of Rochester Medical Center, Department of Radiation Oncology, Rochester, USA 3 Icahn School of Medicine at Mount Sinai, Department of Radiation Oncology and Genetics and Genomic Sciences, New York, USA 4 Albert Einstein College of Medicine, Departments of Pathology and Pediatrics, New York, USA Purpose or Objective Genitourinary (GU) toxicity after radiotherapy (RT) compromises the quality of life of prostate cancer survivors. Predicting RT-induced GU toxicity using clinical or dosimetric information remains challenging. We hypothesized that single nucleotide polymorphisms (SNPs) Poster Viewing : Poster viewing 11: Emerging technologies: radiobiology and physics hand in hand