Abstract P3-19-16: Impact of targeted intraoperative (TARGIT-IORT) tumor bed boost during breast conserving surgery for early breast cancer on breast cancer associated and non-breast cancer associated mortality and morbidity

Abstract

Abstract Introduction: Targeted intraoperative radiotherapy (TARGIT - IORT) as a tumor bed boost during breast conserving surgery is an established option for women with early breast cancer. In a previous study our group could demonstrate a beneficial effect of TARGIT-IORT on overall survival after neoadjuvant chemotherapy driven by non-breast cancer mortality, especially from cardiac or pulmonary diseases. This was in line with results of TARGIT-A trial that demonstrated an improved overall survival after TARGIT-IORT that was driven by other causes of death than breast cancer but in our analysis we could not exclude a selection bias because we had no data regarding pulmonary and cardiac co-morbidities. In this study we present an analysis of breast cancer associated and non-breast cancer associated mortality and morbidity in a lower risk population treated with TARGIT-IORT boost or external boost (EBRT) and with a complete dataset of pulmonary and cardiac co-morbidities at baseline. Material/Methods: In this non-randomized cohort study involving 125 patients with early breast cancer we compared outcomes of 59 patients who received a tumor bed boost with IORT (TARGIT-IORT) during lumpectomy versus 66 patients with external (EBRT) boost. All patients received whole breast radiotherapy. Local recurrence rates, distant recurrence rates, mortality, causes of death and incidence of new pulmonary and cardiac morbidity were compared. The small event rate did not allow a formal comparison, so the results are reported descriptively. Results: There were no statistically significant differences between the two groups regarding age, menopausal status, nodal status, ER status, PR status, HER2 status, tumor size, grading, cardiac or pulmonary diseases and hypertension. Median follow up was 60 months. Local recurrence occurred in 3 cases in the EBRT group (4.5%) and 4 cases in the TARGIT-IORT group (6.8%). Distant recurrences were observed in 5 cases in the EBR group (7.6%) and 3 cases in the TARGIT-IORT group (5.1%). 9 patients in the EBRT group (13.6%) died in the follow-up of 60 months and 6 patients (10.2%) in the TARGIT-IORT group. No death from a pulmonary disease occurred and the incidence of new pulmonary and new cardiac diseases showed no difference between both groups with 3 cases in the EBRT group (4.5%) and 2 cases in the TARGIT-IORT group (3.4%). Death from cardiac disease occurred with an incidence of 7 cases in the EBRT group (10.6%) and only 2 cases in the TARGIT-IORT group (3.4%). 2 patients in the EBRT group died of breast cancer (3.0%) whereas this did not happen at all in the TARGIT-IORT group. Conclusion: This analysis of an average risk group of breast cancer patients well balanced for pulmonary and cardiac co-morbidities demonstrates that TARGIT-IORT as an anticipated boost is not inferior to external beam radiotherapy boost. Trends for an improved overall survival after TARGIT-IORT have been reported before. The trend for a lower incidence of death from cardiac disease is in line with earlier considerations that TARGIT-IORT may induce miR-223 in the peritumoral breast tissue resulting in a downregulation of the local expression of epidermal growth factor (EGF) and a decreased activation of epidermal growth factor receptor (EGFR). This mechanism could explain an effect of TARGIT-IORT on the vascular system. In the currently recruiting TARGIT-B study this aspect will be prospectively investigated. Citation Format: Hans-Christin Kolberg, Stephanie Gutberlet, Jayant S Vaidya, Maja Krajewska, György Lövey, Oliver Hoffmann, Miltiades Stephanou, Cornelia Kolberg-Liedtke. Impact of targeted intraoperative (TARGIT-IORT) tumor bed boost during breast conserving surgery for early breast cancer on breast cancer associated and non-breast cancer associated mortality and morbidity [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-19-16.