S214
Clinical - Breast
ESTRO 2026
Poster Discussion 705
patients with isolated tumor cells pN0(i+) and micro/macro metastases (pN1mic/pN1mac) remain controversial since there is a very low risk of loco- regional recurrence (LRR) without ARRT. We present a population-based study to evaluate the risk of LRR and survival outcomes in BC patients with pN0(i+) and pN1mic/pN1mac, compared to those with pN0, and to evaluate the impact of various adjuvant treatments on outcomes as well. Material/Methods: This population-based study identified women aged 50–80 who underwent breast conservation surgery (BCS) and sentinel lymph node biopsy (SLNB), followed by adjuvant radiotherapy (RT) with T1-3, pN0, pN0(i+), pN1mic and pN1mac M0 BC referred between 2010 to 2015. Primary outcome was LRR. Secondary outcomes were recurrence free survival (RFS), breast cancer specific survival (BCSS) and overall survival (OS). Results: Four thousand and seventy-three patients underwent breast conserving surgery and sentinel lymph node biopsy of whom 3088 (75.8%) had pN0, 276 (6.8%) had pN0(i+), 225 (5.5%) had pNmic, and 484 (11.9%) had pN1mac. Among patients with pN0, 2797 (93.6%) received adjuvant breast RT, 256 (94%) in pN0(i+), 211 (96%) in pN1 mic, and 449 (94%) in pN1mac. Three thousand five hundred and thirty-four (86.8%) patients underwent SLNB only. Other adjuvant treatments received by the entire cohort included adjuvant chemotherapy (30.2%) and endocrine therapy (55.7%). The median follow-up duration was 71.8 months (Interquartile range: 54.2 - 90.3 months). The LRR in the pN0, pN0(i+) , pN1mic andpN1mac cohorts were 114 (3.7%), 9 (3.3%), 24 (3.6%) and 8 (5.0%) respectively. There was no statistically significant difference in LRR among the cohorts (p-value: 0.6). Multivariate cox proportional model showed that the predictors for LRR were tumor stage, tumor grade, lympho-vascular invasion and adjuvant therapy. Conclusion: Loco-regional recurrence was uncommon among patients with isolated tumor cells and micro/macro metastases similar to patients with pN0. However, patients with tumor stage tumor grade lympho-vascular invasion and no adjuvant treatment were at significant risk of loco-regional recurrence. Further analysis is undergoing to study the impact of high tangent radiotherapy and ARRT on LRR. References: Dosani M, Truong PT. Controversies in locoregional management of breast cancer with low volume pN0(i+) and pN1mi nodal disease. Expert Rev Anticancer Ther. 2019 Sep;19(9):803-810 Keywords: Breast cancer, micrometastasis
PROSPECTIVE PHASE II STUDY OF RADIOTHERAPY PLUS CAPACITIVE HYPERTHERMIA IN RECURRENT BREAST CANCER AT THE CATALAN INSTITUTE OF ONCOLOGY (ICO) Marina Arangüena Peñacoba 1 , Evelyn Martínez Pérez 1 , Javier González Viguera 1 , Héctor Pérez Montero 1 , Makarena S. Villalobos Monardes 1 , Andrés C. Moreno Moya 1 , Olalla Santa Cruz 1 , Silvia Comas Antón 2 , ferran guedea edo 1 , Arantxa Eraso Urien 1 1 Radiation Oncology, Catalan Institute of Oncology, Barcelona, Spain. 2 Radiation Oncology, Catalan Institute of Oncology, Badalona, Spain Purpose/Objective: This work reports the experience from two prospective single-arm phase II trials conducted at the Catalan Institute of Oncology (ICO) assessing the safety and efficacy of radiofrequency capacitive hyperthermia (HT) combined with radiotherapy (RT). The primary aim was to evaluate acute and late toxicity using CTCAE v5.0. Secondary endpoints included local control, overall survival (OS) and recurrence-free survival (RFS) at 6 months. The present analysis focuses on the completed superficial HT cohort in patients with recurrent breast cancer. A second study, still enrolling, explores deep HT for pelvic recurrences, locally advanced tumors, and bone metastases. Material/Methods: Thirty women with recurrent breast cancer, either post-mastectomy or after a second breast-conserving surgery, received normofractionated RT together with superficial HT delivered by the Hy-Deep 600 system (Andromedic). Most patients were treated in the adjuvant setting after surgery, while others presented cutaneous recurrences managed with radical intent. Seventy-three percent had previously received radiotherapy. HT was administered twice weekly (interval ≥ 72 h) for 60 minutes per session, immediately after RT. Treatments were performed with curative or palliative intent, and all data were prospectively entered into REDCap. Results: Overall compliance reached 90%. More than half of the patients (56.7%) tolerated HT perfectly. Mild transient discomfort such as burning sensation (13.3%), heat intolerance or sweating (30%) was reported. No grade ≥ 3 HT-related adverse events occurred. Combined RT + HT acute toxicity consisted mainly of radiodermatitis and fibrosis: grade 1 in 16.7%, grade 2 in 46.7%, and grade 3 in 30% of cases. The use of bolus in 40% of treatments might have contributed to higher skin reactions. At 6 months, OS was 95.6% and RFS 87%.
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