Abstract Book

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ESTRO 37

large studies showing benefit of PMRT. PMRT is well known for having a negative impact on IBR, but several papers seem to invalidate these data. This study reports the rate of breast RF after PMRT at our Department, comparing tissue expander (TE) with Pts that underwent mastectomy and immediate TE/PI reconstruction followed by PMRT between June 1997 and December 2011 were retrospectively evaluated. RF failure was defined as a replacement or loss of the implant or conversion to flap. Results Seventy-two and 76 pts underwent IBR with TE and PI, respectively. RF was evaluated in all the pts with PI except 1 who removed her implant during PMRT and in 63 TE-pts since 9 pts never replaced the TE with a PI. Median follow-up from surgery was 107 months. The two groups were comparable for most of the characteristics analyzed. RF occurred in 22/63 (34.9%) TE-pts and 40/75 (53.3%). A statistically significant difference between median interval time to RF was observed with an earlier onset in the TE-pts compared to PI-pts (109.2 vs 157.7 months, p=0.029). The implant weight was the only characteristic maintaining a significant impact on RF at univariate and multivariate analysis. Conclusion In the long run, PMRT after IBR provides an acceptable risk of RF, with an earlier onset for the TE-pts. However, we believe that the choice between PI and TE must be tailored on the individual patient irrespective of potential PMRT. EP-1345 Prevalence of asymptomatic pericardial effusion in breast cancer patients referred for RT M. Arquez-Pianetta 1 , L. Torres 1 , C. Ligero 2 , M. Sousa 3 , M. Arenas 1 , M. Bonet 1 1 Hospital Universitari Sant Joan de Reus, Radiation Oncology, Reus, Spain 2 Hospital Universitari Sant Joan de Reus, Cardiology, Reus, Spain 3 Hospital Universitari Sant Joan de Reus, Radiology, Reus, Spain Acute pericarditis is one of the conditions classically attributed to radiotherapy (RT) in tumours requiring thoracic irradiation. The impact or contribution of previous treatments like chemotherapy (CHT) has not been studied in detail. A high proportion of patients with pericardial effusion (PE) are asymptomatic and the detection of a chronic PE might be an incidental finding. While echography is the gold standard technique to its diagnosis, is not unusual to detect signs of PE in the siumlation CT of breast cancer patients being referred for RT. Objectives To determine the prevalence of radiological signs of PE in a cohort of breast cancer patients previously treated with surgery, with ot wihtout CHT, referred for adjuvant RT. Material and Methods CT images of 151 patients (88 in the CHT group and 63 in the non-CHT group) were reviewed from 2014 to 2015. The presence and volume of radiological signs of PE, assesed by two radiation oncologists and an experimented radiologist, were recorded. The presence of cardiovascular risk factors and intercurrent infective diseases previously to RT were assessed as well. The prevalence of CT signs of PE was compared between CHT and non CHT patients. Results The prevalence of CT signs of PE for the whole grop was 13.25%. All patients were assymptomatic. In the CHT group, 13/88 cases had these signs with a mean volume permanent implant (PI). Material and Methods Purpose or Objective BACKGROUND

of 5.01cc (range: 2,9cc-10cc). In the non-CHT group 7/63 patients had signs of PE, with a mean of 6.81cc (range: 4.5cc – 11.2). There were no statistical differences in prevalence between the groups (p=0.51, chi-square test). Conclusion The prevalence of small volume PE in breast cancer patients referred for RT is not negligible. Chemotherapy does not seem to be a risk factor. A next step of this study is to correlate this findings with the incidence of acute radiation-induced pericarditis in our series and to asses chronic heart toxicity and dosimetric parameters with a longer follow-up. EP-1346 Stereotactic Partial Breast Irradiation for Early Stage Breast Cancer: Early Outcomes S. Kataria 1 , O. Obayomi-Davies 1 , I. Paydar 1 , L. Campbell 1 , S. Collins 1 , S. Rudra 1 , B. Collins 1 1 Georgetown University Hospital, Radiation Medicine, Washington DC, USA Purpose or Objective In carefully selected women with early-stage breast cancer, the preliminary outcomes following accelerated partial breast irradiation (APBI) are comparable to whole breast irradiation. Stereotactic body radiation therapy (SBRT) with fiducial tracking is an attractive APBI treatment option, but limited data are available regarding the outcomes associated with using this technique. We report our institutional experience treating select women with SBRT. Material and Methods Women with DCIS and early-stage (cT1N0) breast cancer treated from November 2008 to September 2015 with a minimum follow up of 2 years were evaluated. Treatments were delivered utilizing the CyberKnife (CK) radiosurgical system. Four to six gold fiducials, tracked in real-time using the CK Synchrony tracking system, were implanted around the lumpectomy cavity prior to the start of treatment. Prior to 2014, the clinical target volume (CTV) was delineated on contrast enhanced CT scans using surgical clips and the visible lumpectomy cavity. Beginning in 2014, the CTV was uniformly expanded by 1 cm, confined to the breast tissue. A 3-5 mm uniform expansion to the CTV was added to generate the PTV. A dose of 30 Gy in 5 fractions was delivered to the PTV. Dosimetry was assessed per institutional protocol, the National Surgical Adjuvant Breast and Bowel Project B-39 guidelines, and TG-101. Clinical examination and mammography were completed at 6-12 follow up intervals. The Harvard Breast Cosmesis Scale was used to assess cosmesis. Fat necrosis was diagnosed on mammography. Results Twenty women (median age: 65 years) were treated with CK over a median 7 days (range 3-13). Treatments began a median of 74 days (range 41-166) after breast conserving surgery. Fourteen women had DCIS and 50% of the tumors were located in the upper outer quadrant of the affected breast. The median treated PTV was 63 cm 3 (range 15-142), the median PTV/breast volume ratio was 8.3% (range 4.1-25.6), and the median prescription isodose line was 83% (range 75-87). At a median follow up of 40 months, locoregional control was 100%. Acute toxicity was rarely observed. A focal Grade 1 telangiectasia was identified in one woman at 52 months. Fat necrosis was diagnosed on mammography in 2 asymptomatic women at 28 and 59 months, respectively. No rib fractures have occurred. Overall, all patients tolerated the treatment without any adverse events and the long term assessment of cosmetic outcomes is ongoing.