Abstract Background: Targeted intraoperative radiotherapy (TARGIT) has become a standard option during breast conserving surgery for selected cases of early breast cancer and over 20,000 patients have been treated in over 300 centers around the world. Although a growing number of patients are presenting with implant breast augmentation, no data has been published regarding the safety of TARGIT with implants in situ. TARGIT IORT as a replacement for whole breast irradiation is an important issue in this context because of the high rates of capsular fibrosis following EBRT in such patients. Methods: We are reporting a case series of 12 patients who received TARGIT during breast conserving surgery for early breast cancer, had undergone breast augmentation with implants before and wanted their implants to stay in situ. Patients were informed that no published data existed and decided on this approach on an individual basis. 3 patients received additional EBRT after TARGIT IORT because of the presence of EIC or LVI. TARGIT IORT was performed using Intrabeam - 50 kV – X-rays delivering 20 Gy prescribed at the surface of the tumor bed during the initial lumpectomy procedure. Results:Patient characteristics are given in table 1. Follow-up varied from 78 months to 3 months. 11 patients presented with invasive breast cancer, 1 patient with DCIS. There were no procedure related complications and none of the patients have needed their implant removed. 1/12 patients (ID 7) was diagnosed with a local recurrence in a distant quadrant after 36 months of follow-up. In 11/12 patients no breast-cancer-related events occurred. Patient characteristicsIDER/PR/HER2GradeSentinel NodesTumor Size (mm)Distance Implant to Tumor (mm)EBRT after IORTFollow up time (months)1pos/pos/neg2pN1mi (sn)95No622pos/neg/neg2pN0 (sn)1913Yes543pos/pos/neg3pN0 (sn)0.85Yes324pos/pos/neg2pN0 (sn)611No155pos/pos/neg3pN0 (sn)71Yes146pos/pos/neg1pN0 (sn)515No117pos/pos/neg2pN0 (sn)7not reportedNo378pos/pos/na1 (DCIS)N/A8not reportedNo789pos/pos/neg2pN0 (sn)15not reportedNo1510pos/neg/neg1pN0 (sn)144No4411pos/pos/neg2pN0 (sn)91No1112pos/pos/neg2pN0 (sn)75No3Table 1 Conclusion: This series of patients with TARGIT during breast conserving surgery for early breast cancer after breast augmentation with implants in situ revealed no safety concerns. Our case series gives some confidence in discussing this option with suitable patients. To expand this series, we are gathering details about other cases from the whole TARGIT group worldwide. Citation Format: Kolberg H-C, Uhl V, Massarut S, Holmes D, Liedtke C, Whineray Kelly E, Lövey G, Vaidya JS. Targeted intraoperative radiotherapy (TARGIT IORT) during breast conserving surgery for early stage breast cancer in patients with breast augmentation with implants [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-12-22.