ESTRO 37 Abstract book

ESTRO 37

S445

5 ASST Papa Giovanni XXIII, Medical Oncology, Bergamo, Italy Purpose or Objective To evaluate outcomes and main prognostic factors after breast conserving surgery (BCS) and full-dose intraoperative radiotherapy (IORT) in patients with age ≥70 affected by early breast cancer (BC). Material and Methods From February 2006 to August 2015, 198 patients aged ≥70 years with diagnosis of early BC underwent BCS and full-dose IORT at PG23 Hospital of Bergamo.IORT was performed by a dedicated linear accelerator NOVAC 7 HITESYS (Italy). The single full-dose of 21 Gy was prescribed at 90% at the tumor bed.We retrospectively evaluated the following outcomes: breast local relapse (BR), defined as any local relapse within the treated breast; distant metastases (DM), defined as any recurrence at the level of organs different from breast and overall survival (OS), assessed from the date of surgery until death to the last follow-up or time of death respectively. For BR free-survival (BRS) and OS we analyzed differences between a group that included and a group that didn’t include the following current PG23 selection criteria: age>50 years, non-lobular histology, tumor size ≤2 cm, pN0 or pNmic, ki67≤20%, non-triple negative receptor status, G1–G2. Statistical analyses were performed by Kaplan–Meier method, differences between groups were made using log-rank test (p value<0.05). Prognostic relevance of the main prognostic factors considered for the outcomes was assessed by means of Cox proportional hazard regression analysis. Results Median follow up was 5.2 years (range 0-9 years).Median BRS, disease-free survival (DS) and OS was 1,5 years.We evidenced 15 patients (7,5%) with BR: 11 patients (73%) with true local relapse, 4 (26%) with new ipsilateral recurrences. Twelve patients (6%) had DM: 6 with nodal recurrences and 6 with bone and visceral metastases.Seventeen patients (8,5%) died: 6 patients (35%) for BC. We evidenced significant differences both for BRS (p=0.04) and OS (p=0.03) between the group that included and the group that didn’t include the current PG23 selection criteria, with a significantly lower relapse rate in the first one. According to Cox proportional-Hazard regression analysis, for BRS most important prognostic factor resulted to be ki67% (p= 0.01). For OS most important prognostic factors were ki67%, pN and margin status. Conclusion The use of postoperative RT in the elderly is a matter of debate, particularly due to comorbidities and problems concerning the distance from RT centers to attend a daily treatment. However several studies still evidence that complete omission of RT failed in terms of local tumor control also in an elderly patient population.In this contest full-dose IORT in a well-selected group of elderly patients with early BC, in our preliminary analysis, showed to be a valid alternative to the omission of RT for a good local control. Also in this subgroup of patients, the role of Ki67% confirmed to be fundamental as selection criteria. PO-0851 Radiotherapy in patients with cardiac implantable electronic devices:clinical and dosimetric aspects G. Riva 1 , O. Alessandro 1 , R. Spoto 1 , A. Ferrari 1 , C. Garibaldi 2 , F. Cattani 2 , N. Colombo 3 , F.L.F. Giovenzana 3 , C. Cipolla 3 , M. Winnick 4 , M. Persiani 1 , F. Castelluccia 1 , M. Sarra Fiore 1 , R. Orecchia 5 , B.A. Jereczek-Fossa 1 1 Istituto Europeo di Oncologia - IEO, Radiotherapy, MIlan,

Italy 2 Istituto Europeo di Oncologia - IEO, Radiation Research Unit, MIlan, Italy 3 Istituto Europeo di Oncologia - IEO, Department of Cardiology, MIlan, Italy 4 Mayo Clinic, Cardiovascular Division, Rochester, USA 5 Istituto Europeo di Oncologia - IEO, Scientific Direction, MIlan, Italy Purpose or Objective As a result of aging, the number of patients with cardiac implantable electronic device (CIED) that requires radiotherapy (RT) continues to rise. RT can compromise electronic components of CIED resulting in transient malfunctions or even causing their permanent damage. Thus, presence of CIEDs could make more difficult management of these patients before and during RT. Aims: To evaluate RT-related malfunctions of CIED in a cohort of patients who underwent RT in our clinic from June 2010 to December 2016. Material and Methods We retrospectively analyzed 93 RT treatments in 63 patients with CIEDs referred to our clinic from June 2010 to December 2016. Patients were treated with 3- Dimensional Conformal RT, Intensity-Modulated RT and Stereotactic RT. We collected clinical characteristics of cancer, models of CIEDs, and total RT dose to tumor and radiation energy. Radiation dose to device and CIED dysfunctions after RT were evaluated. Then, we performed subgroup analysis of 48 RT treatments (32 patients) on chest and neck plus on 13 RT treatments (12 patients) with 18 MV neutron-producing photon energy, all of them considered as high-risk treatments. Results During 7 years covered by the study the number of treatments of patients with CIEDs who underwent RT in our Institute increased 6-fold from 0.2% in 2010 to 1.2% in 2016. Two patients, both with Implantable Cardioverter Defibrillators (ICDs)and treated with neutron-producing energy photon beam, experienced adverse events of CIEDs: an altered electrode sensing and a reprogramming of device. Both devices received a maximum dose of around 2.1 Gy. Patient A, male, experienced a reprogramming of ICD during RT when he reached a total dose of 32 Gy to the tumor with a prescription dose of 58 Gy. The last sessions of RT were performed with the presence of a cardiologist and the CIED switched off during the irradiation. No more adverse events were reported. Patient B, female, experienced an altered sensing after 11 months from the end of RT. The device had to be removed and replaced with a new ICD. No other patient had a life-threatening device-related adverse events.