Abstract P3-19-24: Long-term follow-up results of intensity modulated radiotherapy in early-stage breast cancer patients

Abstract Introduction: Early breast cancer patients with complex anatomy received adjuvant intensity modulated radiotherapy with helical tomotherapy (IMRT-HT) in our Institute. The aim of this study was to evaluate our results in terms of local control, overall survival, progression free survival and adverse events. Materials and methods: This study is a retrospective data analysis, enrolling patients treated with helical tomotherapy irradiation technique. Overall survival (OS) and progression free survival (PFS) curves were plotted with Kaplan-Meier method. We also analyzed the OS and PFS data by molecular subgroups. Long-term toxicities were evaluated using Common Terminology Criteria of Adverse Events (CTCAE) version 4.0. Multivariable analysis was performed to determine the predictors of the toxicities. Results: Between 2009 and 2015, 174 patients with 194 treated breasts were irradiated with helical tomotherapy. The median follow-up was 65 months. The 8-year OS was 89,2 % (IC95: 83.5% - 95.4 %), the 8-year PFS was 85,4% (IC95: 80.2%- 91%). The best therapeutic response shown by the 5 year OS data was in the HER2 receptor positive subroup 95% (IC95: 85.9% - 100%). Long-term skin toxicity was the most common long-term side effect, seen in 20.7% of the patients. 5 patients had second primary breast cancer, always located at the contralateral breast. In multivariant analysis, BMI>25 kg/m2 was found to be a predictor of skin toxicity, and pre-existing cardiovascular disease was independently associated with the risk of cardiovascular toxicity. Conclusion: HT can be safely used for adjuvant breast cancer irradiation. In patients with complex anatomy, HT improves clinical target volume coverage and reduces the dose to OARs. Further prospective studies with long follow-up are needed to confirm and validate these results. Citation Format: Zita Zolcsák, Pierre Loap, Alain Fourquet, Alexandre Arsene Henry, László Landherr, Péter Hamar, Youlia Kirova. Long-term follow-up results of intensity modulated radiotherapy in early-stage breast cancer patients [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 P3-19-24.