Effect of distribution of ipsilateral supraclavicular lymph node metastasis on target volume delineation in breast cancer : an analysis of 55 patients

Abstract

Objective To retrospectively investigate the effect of the distribution of supraclavicular lymph node metastasis ( LNM) on clinical target volume ( CTV) delineation in radiotherapy for breast cancer. Methods Fifty-five patients with breast cancer who underwent helical computed tomography ( CT) scan and were diagnosed with supraclavicular LNM were enrolled as subjects and their CT images were collected. The metastatic lymph nodes in 55 patients were recreated proportionally on the CT images of a standard patient with breast cancer with reference to normal anatomy in the supraclavicular area. The relationship between the distribution of supraclavicular LNM and the CTV recommended by the Radiation Therapy Oncology Group (RTOG) and other literature was analyzed. Results Sixty percent of LNM were pathologically confirmed and distant metastasis occurred in 64% of supraclavicular LNM. Ninety-one percent and eighty-two percent of patients had centers of LNM in the internal and external regions of the supraclavicular area, respectively. Sixty-six percent of patients had LNM located in the subclavian venous confluence. The CTV recommended by literature covered the centers of all LNM in only 20%-42% of patients, while the CTV recommended by the RTOG guide covered the centers of all LNM in only 26% of patients. Seventy-one percent and sixty-six percent of patients had the centers surpassing the lateral and posterior edges of the CTV, respectively. According to the distribution of LNM mentioned above, we expanded the CTV in the supraclavicular area by extending the lateral and posterior edges to the natural anatomical barriers and the new CTV covered the centers of all LNM in up to 82% of patients. Conclusions The locations of supraclavicular LNM surpass the range, particularly the lateral and posterior edges, of the CTV defined by the RTOG guide. Therefore, the CTV in the supraclavicular area needs to be extended to cover those regions mentioned above. Key words: Breast neoplasm; Supraclavicular nodal metastases; Prophylactic radiotherapy; Target volume delineation