1078 - <em>Re</em>duced-vo<em>l</em>ume Irradiation to the <em>Ax</em>illa in Breast Cancer Patients with Sentinel-Lymph-Node Metastases (RELAX): A Single-Arm, Phase 2 Study
Presenter(s)
L. Zhang, J. Luo, W. Lui, X. Wang, W. Shi, J. Meng, J. Ma, X. Guo, Z. Yang, and X. Yu; Department of Radiation Oncology, Fudan University Shanghai Cancer Center; Department of Oncology, Shanghai Medical College, Fudan University; Shanghai Clinical Research Center for Radiation Oncology; Shanghai Key Laboratory of Radiation Oncology, Shanghai, China
Purpose/Objective(s): Several randomized trials have demonstrated the safety of omitting complete axillary-lymph-node dissection (ALND) in invasive breast cancer patients who had sentinel lymph node (SLN) metastases. However, the necessity and the extent of target volume for regional nodal irradiation (RNI) remains uncertain. This study aimed to evaluate whether reducing the target volume of RNI by including only axillary level 1~2 radiotherapy could achieve equivalent axillary control while reducing associated complications in breast cancer patients with 1 - 2 SLN metastases.
Materials/Methods: Patients diagnosed with invasive breast cancer, with clinical node-negative but 1-2 micro- or macro-metastases in the sentinel lymph nodes ] and without ALND, were prospectively enrolled in this singe-arm, phase 2 study. All patients received modern adjuvant systemic therapy. Intensity-modulated radiation therapy (IMRT) was used, with a prescription dose of 50 Gy in 25 fractions to the ipsilateral chest-wall or breast plus axillary level 1~2 area. If patients received breast conserving surgery (BCS), an additional 10-16 Gy boost was delivered to the tumor bed. The clinical target volume was contoured according to the Radiation Therapy Oncology Group (RTOG) breast cancer atlas. Radiation therapy plans were quality-reviewed pretreatment. The primary end point was 5-year axillary recurrence. The secondary end point was locoregional nodal recurrence, disease-free survival (DFS), overall survival (OS), adverse events, and quality of life.
Results: Between January 2015 and December 2022, 467 eligible patients were enrolled. The median age was 46 years (range, 40-53). A total of 130 (27.8%) patients underwent mastectomy and 337 (72.2%) had BCS. Additionally, 301(64.5%) patients were diagnosed with pT1-stage tumor. The median number of sentinel nodes was 4, and 406 (86.9) patients had one sentinel lymph node metastases after SLNB. All patients received irradiation to chest wall/breast and axillary level 1- 2 area. Moreover,15 (3.2%) patients received supraclavicular irradiation and 27(5.8%) received internal mammary node irradiation. At the data cutoff (Jul 31, 2024), the median follow-up was 61 months (range, 7-113). In total, 3 patients had axillary recurrence and 6 patients had locoregional recurrence. The 5-year axillary recurrence rate was 0.8%, and the 5-year locoegional recurrence rate was 1.3%. During the follow-up, 12 patients experienced distant disease and 7 patients died. The 5-year DFS and OS was 92.3% and 98.8%, respectively.
Conclusion: Among patients with one or two SLN metastases without ALND after breast-conserving surgery or mastectomy, reducing the target volume of RNI to include only axillary level 1~2 provided favorable axillary control, with an extremely low axillary recurrence rate. These findings potentially support reducing the target volume of regional nodal irradiation in breast cancer patients with SLN metastases who did not undergo further ALND.