Patterns of supraclavicular area failure after mastectomy in breast cancer patients: implications for target volume delineation

Purpose To characterize the pattern of post-mastectomy supraclavicular lymph node (LN) metastases in patients with breast cancer (BC) and to provide insights for individualized clinical target volume delineation for radiotherapy. Methods We retrospectively analyzed 88 patients with BC who developed post-mastectomy regional LN metastases. The affected regional LNs were categorized as the ipsilateral medial supraclavicular LN area (IMSC-LN), ipsilateral lateral supraclavicular LN area (ILSC-LN), ipsilateral infraclavicular LN area (IIC-LN), and ≥2 groups in the ipsilateral clavicular LN area (MMIC-LN). Clinical characteristics were included in a multivariate analysis to identify risk factors for clavicular LN metastases. Results The ILSC-LNs (68.2%) were the most common metastatic site. IMSC-LN metastases showed a significant association with estrogen-receptor (ER) negative status, left-sided BC, and positive axillary LNs. Tumor size ≥2.4 cm and Her2 type were predictors of ILSC-LN metastases. Additionally, tumor size ≥2.4 cm, and level I ipsilateral axillary metastases were associated with MMIC-LN metastasis. Conclusion ILSC-LN was the most frequently affected group of supraclavicular lymph nodes. ER-negative status, left-sided BC, tumor size, and positive ipsilateral axillary LNs are potentially associated with the pattern of supraclavicular LN metastatic involvement.