2967 - Variability and Factors Impact Irradiation Area of Regional Lymph Node in Low-Burden Breast Cancer Patients after Omitting Axillary Dissection: Experience from a High-Volume Center

03:00pm - 04:00pm PT

Hall F

Screen: 10

Presenter(s)

Li Li, - Department of Radiation Oncology,Ruijin Hospital,Shanghai Jiaotong University School of Medicine,Shanghai 2000025,China, Shanghai,

L. Li¹, W. X. Qi², J. Y. Chen³, G. Cai², L. Cao³, S. Y. Zheng², and S. Wang⁴; ¹Department of Radiation Oncology,Ruijin Hospital,Shanghai Jiaotong University School of Medicine,Shanghai 2000025,China, Shanghai, China, ²Department of Radiation Oncology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China, ³Shanghai Key Laboratory of Proton Therapy, Shanghai, China, ⁴Ruijin Hospital, Shanghai Jiao Tong University, School of Medicine, SHANGHAI, China

Purpose/Objective(s):

Sentinel lymph node biopsy (SLNB) has been the standard treatment procedure for clinically node-negative (cN0) breast cancer (BC). Three randomize trials (Z0011, AMAROS and SENOMAC) have confirmed that patients with low-burden sentinel lymph node metastasis can be safely omitted axillary lymph node dissection who receive adjuvant radiotherapy. However, these published research papers have been insufficient to accurately assess the recurrence risk in this patient population, leading to variability in adjuvant radiotherapy volume across different studies. Therefore, the optimal adjuvant regional nodal irradiation (RNI) volume for early-stage BC with low-burden sentinel lymph node metastasis remains undetermined. Therefore, we performed present study to analyze and explore the factors that influence the decision of regional nodal irradiation in this patient population.

Materials/Methods:

A retrospective single-institution review was performed in breast cancer patients eligible for enrollment from 2018 to 2024. Univariate and multivariate logistic regression analysis were used to analyze the clinicopathological factors influencing different radiotherapy decisions.

Results:

Among 215 eligible patients, 190 (88.4%) received regional lymph node radiation: 83.7% to the clavicle, 66.5% to the internal mammary region, and 80% to the axillary region. Univariate analysis linked SLN positivity (>1), adjuvant chemotherapy, histologic grade III, and Ki-67 =14% to clavicle irradiation. Multivariate analysis identified SLN >1 (p=0.018) and histologic grade (p=0.042) as independent predictors. For axillary irradiation, Ki-67 =14% was the sole risk factor (ORadj 2.26, 95%CI: 1.00-5.13, p=0.05). Univariate analysis suggested tumor size, SLN positivity, adjuvant chemotherapy, PR status, triple-negative status, histologic grade, and Ki-67 as potential risks for internal mammary irradiation, but multivariate analysis found no independent predictors.

Conclusion: For early-stage BC with low-burden sentinel lymph node metastasis, the number of positive sentinel lymph nodes and histological grade were two important factors for radiation oncologists to decide the irradiation of clavicle lymph node region, while ki-67 index was the only risk factor for receiving axillary lymph node area irradiation. No significant factors could be found associated with inner mammary node irradiation, suggesting whether inner mammary node irradiation remained controversial among this patients population, and further studies are clearly suggested to investigate this issue.