EP-1200: Partial breast irradiation and stereotactic body radiation therapy with Exactrac in breast cancer patients

ESTRO 33, 2014 the tumour cavity (5-8 fractions,2 Gy/ fraction) post EBRT (40 Gy/ 15 fractions) was performed based on clinical history, tumour position on pre surgery mammogram and position of surgical scar. Contouring of the tumour bed was done by the radiation oncologist along with the surgeon to ensure accuracy. COP and COE 3-D conformal plans were generated for each of the treated patients, all 150 plans were analysed. TCV, CEM maximum field size, area,toxicity and electron energy was recorded. COP and COE plans were analysed and conformity index (CI) to the TCV, and homogeneity index(HI) were compared and pearson’s correlation coefficient (correl) to TCV was calculated. Volume of irradiated tissue between COP and COE were compared. Lung dose (V20% and V50%) were compared between the two conformal techniques. Results: Mean age was 51 yrs range (29-79 yrs). Mean of maximum CEM field size was 7.57 cm, mean treatment area on skin 54.66 sq cm. 52% received 9 Mev electrons and 16 % had Gr2 or above skin toxicity. Mean clinical tumour size was 3.05cm vs 2.6cm for pathological size with a significant correlation (-0.34; p=0.02). Mean TCV was 35.39 with significant Correl between COP and COE treatment volumes (0.82 and 0.72) respectively . HI for COP was significantly better than that for COE (6.8 vs 1.14, p=0.02). Conformity Index was also better for COP vs COE (0.27 vs 0.08; p<0.01). Mean Lung V50% was similar for COE and COP plans (0.34 vs 0.30) whilst V20% was significantly better for COP plans (3.18 vs 0.87; p<0.01). Conclusions: COP plans had the best CI, comparable V50% Lung dose and better V20% lung dose. Although CEM is currently used, COP technique could be implemented for better TCV coverage with comparable toxicities. Better HI and CI with skin sparing photons could potentially reduce post radiation dermatological toxicities. EP-1199 Hypofractionated radiotherapy and concomitant boost in breast cancer patients using 3-D conformal radiotherapy J. Valero Albarrán1, R. Ciervide Jurio1, C. Eito Valdovinos1, M. GarciaAranda Pez1, M. Lopez Gonzalez1, E. Sanchez Aggar1, O. Hernando Requejo1, M. Herrero Conde1, L. García Estevez1, C. Rubio Rodríguez1 1 Hospital Universitario Madrid Sanchinarro - Grupo Hospital de Madrid, Radiation Oncology, Madrid, Spain Purpose/Objective: To report the impact of hypofractionated radiotherapy (RT) in three weeks to the whole breast with a concomitant boost in patients undergoing breast-conserving surgery (BCS) using 3-D radiotherapy with multiples fields in terms of dosimetric parameters, acute skin toxicity and cosmesis results. Materials and Methods: Patients who underwent BCS +/- axillary lymphadenectomy on cancer stage 0, I, II or III breast cancer were eligible for hypofractionanted RT. There were no restrictions on breast size or the use of previous cytotoxic chemotherapy for otherwise eligible patients. Patients with expander or immediately breast reconstruction were excluded. All patients received RT to the whole breast with concomitant boost irradiation of the tumor bed. Prescription dose were 40.5 Gy and 48 Gy respectively, delivered in 15 fractions (2.7 Gy and 3.2 Gy per fraction). Planning treatment was based on paired tangential fields with the addition of reduced tangential fields used to increase the dose homogeneity distribution and the dose to the tumor bed. Treatment verification was performed with Portal Images in all treatments. Dosimetric parameters of heterogeneity (V107 and maximium dose) and the coverage of PTV (V95) of the prescription dose were recorded for each treatment plan. No more than 10% of the heart and 15% of the lung volume was allowed to receive >16Gy. Skin toxicities were recorded after the completion of radiation and one month later according to RTOG acute radiation morbidity scoring criteria. Cosmetic outcomes were assessed as excellent/good or poor. This protocol was approved by the Institutional Review Board. Results: Between May and September 2013, a total of 50 women with a mean age of 51 years (range 33-76) were analyzed. The average fields used was 4.5 (range 3-8). The mean breast volume that received ≥ 95% of the prescription dose was 98.3 % and 0.5% was the average of volume that received ≥ 107% of the prescription dose. The mean maximum dose to the breast was 52.8 Gy and the mean V16 in the ipsilateral lung was 12.1%. In the left tumor patients, the mean heart V16 was 2.13%. Acute toxicity was confined to the skin and Grade 0-1 skin toxicity was present in 66% of patients. Grade 2 skin toxicity was reported in 28% of patients. No grade >3 skin toxicity was observed. Cosmetic assessment was goodexcellent in the 100% of patients. Conclusions: Hypofractionated radiotherapy in three weeks to the whole breast with a concomitant boost in patients undergoing breastconserving surgery (BCS), using 3-D radiotherapy with multiples fields allow acceptable outcomes in terms of dosimetric parameters, acute

S55 toxicity and early cosmesis results and is a good approach for LINAC schedule due to the reduction of 15 days when compared to standard RT treatment of breast cancer. A long- term follow up data are needed to assess late toxicity, cosmesis, and clinical outcomes. EP-1200 Partial breast irradiation and stereotactic body radiation therapy with Exactrac in breast cancer patients R. Ciervide1, J. Valero Albarrán1, M. Garcia-Aranda1, M. Lopéz Gonzalez1, J.U.A.N. García1, E. Sanchez Augar1, O. Hernando Requejo1, I. Calvo1, M. Fernandez Abad1, M. Rubio1 1 Hospital Universitario Madrid Sanchinarro - Grupo Hospital de Madrid, Radiation Oncology Department, Madrid, Spain Purpose/Objective: Asses the feasibility of applying stereotactic body radiation therapy SBRT with Gating in patients with breast cancer of very good prognosis (VGP) with an accelerated fractionation (5 fractions of 6 Gy) in alternate days. Quantify acute toxicity according to RTOG and CTCAE scales. Materials and Methods: Women with more or equal than 60 years-old, pT1(<2cm) after breast conserving surgery, surgical margins ≥2mm, pathological confirmation of infiltrating ductal carcinoma, pN0, ECOG 01 and luminal subtype were eligible. An Internal fiducial marker (Visicoil®) was placed close to the surgical bed, prior to simulation. Patients underwent CT simulation in supine position with an immobilization device and infrared spheres on the skin, as external fiducials. PTV and organs at risk were outlined at CT planning. PTV and organs at risk were outlined. CTV was created based on the clips fitted in the surgical bed by the surgeon, the surrounding fibrosis and the presence of seroma. A 0,5 cm of expansion was added to generate PTV. The prescription dose was 30 Gy in 5 fractions of 6 Gyonce a day to the PTV in alternate days. Subsequently, a tridimensional conformal radiation therapy planning with iPlan Net® was performed. DVH were assessed and approved according to ASTRO recommendations for PBI constraints. In addition, patients with a PTV volume ≥ 1/3 of ipsilateral breast total volume (IBTV) were excluded. During the delivery of the treatment and considering the respiratory cycle (RC), the intrafraction control of PTV motion was assessed based on the correlation of the internal marker and the external fiducials with Novalis Exactrac Gating System. PTV was irradiated in a selected gated area of the RC. Acute toxicity outcomes were assessed according to RTOG criteria. This investigational project was approved by the Institutional Review Board. Results: From February to September 2013, 8 patients were accrued. Median age was 75 years (range 62-86). There were 4 left breast and 4 right breast cancers. Tumors were 100 % hormone positive. Median tumor size was 1,2 cm (range 0,8-1,3cm). Regarding dosimetric outcomes, the mean of PTV coverage was 99,4%, mean of PTV D max was 32,5 Gy, mean of PTV dose was 30,8 Gy, mean of PTV volume was 93,6cm3 and the mean of ipsilateral breast volume was 813 cm3. None of patient had a PTV volume higher than 1/3 of IBTV. The mean of contralateral breast dose was 0,46 Gy and the mean of V9 of ipsilateral lung was 2,44%. In left tumor patients, the mean heart V1,5 was 31,23 %. The mean of skin D10 cm3 was 24,6 Gy. Acute toxicity was confined to the skin and Grade 1 skin toxicity was present in 87,5 % of patients. No Grade≥2 skin toxicity was reported. Cosmetic assessment was good-excellent in the 100%of patients. Conclusions: SBRT with Exactrac Adaptive Gating in patients with breast cancer of VGP is feasible. Dosimetric outcomes met all the criteria with an excellent acute toxicity in all the sample EP-1201 Inspiration gating - improving left breast coverage for patients with anterior heart position: The RPM advantage A. Kaplinsky1, V. Pyatigorskaya1, I. Gelernter2, H. Granot1, M. Ben-Ayun1, D. Alezra1, Z. Symon1, M. Ben-David1 1 Sheba Medical Center, Radiation Oncology, Ramat-Gan, Israel 2 Tel- Aviv University, Statistical Lab School of Mathematics, Tel-Aviv, Israel Purpose/Objective: Adjuvant radiotherapy for breast cancer (BC) reduces local recurrence and improves survival. In patients with left sided BC, anterior heart position may cause inadequate coverage of the breast due to heart shielding. Respiration gating using the Varian Real-Time Position Management (RPM) system enables pushing the heart away from the tangential field during deep inspiration and thus optimizing the treatment plan and target coverage.