Abstract Book

S737

ESTRO 37

Conclusion The ESTRO defined margin of 5mm covers IMN nodes in only 72% of the treatment naïve patients and a larger 7mm margin might be required to cover the target in the same patients. No nodes were found posterior to the vessel and the margin can be safely shaved till the lung/wall interface posteriorly. EP-1349 Acute skin toxicity of hypofractionated whole breast radiotherapy in large-breasted patients V. Carrizo Ibarra 1 , V. García Reglero 1 , J.E. Baquedano 1 , E. García Alonso 1 , M. Mira Flores 1 , B. Domingo 2 , O. Torne 2 , P. Vicente 2 , J.A. Carceller Vidal 1 1 Hospital Universitario Arnau de Vilanova- Lleida, Radiation oncology department, Lleida, Spain 2 Hospital Universitario Arnau de Vilanova- Lleida, Radiation oncology- nursery department, Lleida, Spain Purpose or Objective The objective of this study is to evaluate skin toxicity in obese and large- breasted women with an early breast cancer treated with hypofractionated schedule (dose 40.05 Gy to 2.67 Gy per session) after breast conserving surgery. Material and Methods From 2012 to 2015, a total of 350 breast cancer patients were treated with 3-dimensional conformal radiotherapy with a hypofractionated schedule. The patients received 40,05 Gy in 15 daily fractions. Acute skin toxicity was monitored during and after radiotherapy according to RTOG scale. Results Out of the 350 patients were treated in our centre, 34.85% of the patients (122) had a breast volume (PTV) of > 1000 cc. and 12% (42) had PTV > 1500 cc. In the subgroup of patients with PTV within 1000 cc and 1500 cc, 70.9 % presented acute toxicity grade 1 and 27.8% presented acute toxicity grade 2. In these patients, grade 2 toxicity was localized in 38% in the submammary region and 62% in the axillary region. In the subgroup of patients with a PTV > 1500 cc, 32,6% presented acute toxicity grade 1 and 67,9% presented acute toxicity grade 2. In these patients, grade 2 toxicity was localized in 80% in the submammary region and 20% in the axillary region. No grade 3 toxicity was reported in any of the subgroups. Skin toxicity was treated with moisturizing cream, corticosteroid ointments or healing cream if needed with good cosmetic results after 15 days of finishing the radiation treatment.

effectiveness ratio (ICER) was calculated to verify the cost against the clinical outcome. Finally, a simulation of public payer’s expenditures for the treatment of early breast cancer with APBI and WBI in 2013 and 2025 has been conducted. Results The average cost of treatment with APBI is lower than for WBI, even assuming a potential increase in the unit price of the former procedure. There was no additional health benefit of WBI and the calculation of cost-effectiveness was based on the absolute difference in overall local control rate. However, this difference (0.92% versus 1.44%) was fairly minimal and was not identified as statistically significant during 5 years. Conclusion The use of APBI as an alternative to WBI in the treatment of early breast cancer would substantially reduce healthcare expenditures in both 2013 and 2025, even assuming an increase in the price per single APBI procedure. EP-1348 Target Delineation Of Internal Mammary Nodes in Locally advanced Breast Cancer G. Narayanan 1 , R. Kumar 2 1 Vydehi Institute of Medical Sciences, Radiation Oncology, Bangalore, India 2 Vydehi Institute of Medical Sciences, Radiation Oncology, gurgaon, India Purpose or Objective Regional nodal irradiation as a component of both postmastectomy and postl umpectomy radiation has been shown in numerous randomized trials and meta-analyses to have a significant impact on locoregional control, breast cancer mortality, and, in some cases, overall survival. A recent meta-analysis showed an improvement in overall survival on addition of internal mammary nodes as a target in nodal radiation. There is paucity on data on IMN contouring, though ESTRO recommends a margin of 5mm around the internal mammary vessels, there is no objective proof of what percentage of nodes would get covered in a treatment naive patient when we use a 5mm margin. We intend to investigate the same. Material and Methods 30 clinically node positive non metastatic consenting breast cancer patients were subjected to a diagnostic contrast-enhanced CT, reconstructed to 1.25 mm slice thickness. Internal mammary vessels were contoured on the treatment planning system and an isotropic margin of 2.5, 5, 7 and 10mm were given. With each margin, percentage of the covered or missed nodes was recorded. Total number of nodes and its location with respect to the tumor location was also recorded. Results 147 nodes in total were contoured in the studied 30 treatment naïve patients. 8%, 72%, 96% and 100% of the nodes were covered using margins of 2.5, 5, 7 and 10mm margins respectively. Nodes were located anteriorly medially or laterally and no nodes were found posteriorly. Maximum Nodes were found in the 1 st , 2 nd and 3 rd intercostal space with an occasional node in the 4 th 5 th and 6 th spaces