Abstract PO2-22-03: Reirradiation for locally recurrent breast cancer: a long-term single centre experience

Abstract Background: About 10–15% of patients with breast cancer will eventually develop an ipsilateral breast recurrence. The management of cancer relapse in previously irradiated tissues is a challenging therapeutic issue, and data on breast re-irradiation are currently lacking. Hence, the aim of this work was to report our experience with breast re-irradiation for non-metastatic recurrent breast cancer. Material and Methods: All patients who underwent a breast or chest wall re-irradiation in the Institut Curie, Paris, France between 2003 and 2019 were identified. Those who underwent re-irradiation only in other volumes than the ipsilateral breast were excluded. Local recurrence-free (LRFS), overall survival (OS), disease-specific survival (DSS), progression-free survival (PFS), and metastasis-free survival (MFS) were evaluated. Physician-reported acute and late toxicities were assessed using the Common Terminology Criteria for Adverse Events (CTCAE) 5.0. Results: Between 2003 and 2019, 21.372 patients underwent a breast irradiation in our institution. Of these, 453 received a new irradiation to the controlateral breast and/or lymph nodes, 105 to the homolateral lymph nodes without breast/chest wall re-irradiation and 28 received a second course of radiotherapy (RT) to the homolateral breast. These 28 patients were included in this study. Median follow up after re-irradiation was 45.5 months (IQR 33.5-79.75 months). The median age at the time of second breast RT was 63 years (IQR, 49-78). The median RT dose to the breast/chest wall was 60 Gy (interquartile range (IQR) 50-66 Gy) for the first irradiation and 48 Gy (IQR 30-50 Gy) for the second. The median cumulative dose was 100 Gy (IQR 92-114 Gy). The median time between the two courses of RT was 47 months (IQR 22.75-109.5 months). Eighteen (64%) patients were treated with a curative intent and 10 (36%) for palliative purposes. Ten (36%) had a macroscopic breast residue at re-irradiation. The second RT course was performed with electrons, photons and a combination of both in 13 (46%), 8 (29%) and 6 (21%) patients, respectively. At 2 years, LRFS, OS, DSS, PFS and MFS were respectively 59%, 79%, 82%, 50% and 75% in the whole cohort. 2-year-LRFS (72% vs 31%, p=0.02), OS (94% vs 50%, p 0.01), DSS (94% vs 56%, p 0.01) and PFS (61% vs 20%, p=0.02) differed significantly between patients treated in a curative or in a palliative intent, but not MFS (78% vs 69%, p=0.77). Among patients, 8 (29%) remained relapse-free 5 years after the second course of RT. Only one patient experienced an acute grade 3 adverse event (dermatitis), and 1 presented a late grade 3 one (skin fibrosis). One patient with major cardiovascular risk factors died of myocardial infarction 13 months after the second left breast irradiation. Conclusion: Breast or chest wall re-irradiation appears to be feasible with good disease control in patients treated with a curative intent, and acceptable toxicity rates. In addition, a significant number of patients were disease-free 5 years after the second course of RT. Prospective larger data with longer follow-up are needed to confirm these findings. Citation Format: Jérémy Baude, Rémi Dendale, Alain Fourquet, Youlia Kirova. Reirradiation for locally recurrent breast cancer: a long-term single centre experience abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-22-03.