ESTRO 36 Abstract Book

S848 ESTRO 36 _______________________________________________________________________________________________

Conclusion Irradiation of breast and RLNs without IM in prone position in women with large, pendulous breasts is feasible and safe. Including IM chain in radiotherapy plan significantly increases doses in lungs and heart but acceptable values may be achieved in some of patients. Dynamic techniques show no benefit in comparison to 3D CRT. EP-1573 TBI and TMI treatment comparison using bilateral and anteroposterior delivery techniques E. Sandrini 1 , C.M. Da Silva 1 1 Clínicas Oncológicas Integradas, Medical Physics - Radiotherapy, Rio de Janeiro, Brazil Purpose or Objective Evaluate doses in organs at risk and target volume coverage of patients undergoing total body irradiation (TBI) or total marrow irradiation (TMI) treatment in supine and lateral decubitus. The TBI and TMI treatment are an old kind of treatment that normally uses 2D calculation. This work used a 3D calculation with heterogeneity correction as the same way of the old technique (two opposite fields), but with a CT it’s possible to estimate the dose in OAR and the target coverage. Material and Methods Five partial (3/4) total body CT image were used to plan a TBI treatment with two different setups: supine and lateral decubitus. The plans had two opposite fields with 6MeV and their collimator rotated by 45 degrees, the extended SSD used was 350cm, it was used Acurus XB dose calculation algorithm and the prescription was 12Gy in 6 fractions. For each CT it was drawn the body, bones, lungs, heart, kidneys, liver and eyes. It was investigated the following aspects: (A) body coverage (TBI treatment), (B) bone coverage (TMI treatment), (C) dose homogeneity index (DHI) defined as the ratio of dose received by 90% of the volume (D90) to the minimum dose received by 10% of the volume (D10), (D) mean dose of organs at risk: lungs, kidneys, heart and liver and (E) maximum dose in eyes. Results It was observed that when using supine decubitus instead of lateral decubitus the D95 of body decreases 2%, and D95 of bones didn’t change; The DHI of TBI and TMI treatment was reduced by 10%; The crystalline maximum dose and heart mean dose was increased by 20% and 3%, respectively; And the mean dose of kidney, lung and liver was reduced by 10%, 6% and 4%, respectively.

Conclusion This work indicates that the target coverage and DHI aren’t significantly affected by the patient positioning. Although the bilateral technique increased the eyes and heart dose, it was observed a decrease in lung, kidney and liver dose. So as the pulmonary complication is renowned as the major causes of mortality following TBI, the best positioning for this kind of treatment is supine decubitus. EP-1574 Helical Tomotherapy for Bilateral Breast Cancer Patients: 3-Years Single Centre Experience F. Ertan 1 , M. Altundag 1 , H. Abanuz 1 , S. Duzgun 1 1 Ankara Oncology Hospital, Radiation Oncology, Ankara, Turkey Purpose or Objective The present study aims to evaluate dose distribution characteristic using helical tomotherapy (HT) for patients with bilateral breast cancer. Material and Methods From January 2013 to December 2015, 12 patients were treated with tomotherapy. The target volume includes different parts for each patient and was shown in Table- 1. During CT simulation, the patient was positioned supine on a breast board and CT slices were obtained at 3 mm intervals extending from the chin to the upper abdomen during free breathing. Tomotherapy planning parameters; the field width, modulation factor and pitch, were assigned to 5cm, 2 and 0.287, respectively, for all plans. To protect critic organs at maximum level, the complete block was applied. The delivered dose was 50Gy within 25 fractions for 11 patients and, simultaneous integrated boost technique was used within 60Gy to boost and 50Gy to PTV in 25 fractions for 1 patient. Treatment planning