Abstract
BackgroundThere is a discrepancy about the metastatic rate of internal mammary lymph nodes (IMNs) between clinical and pathologic findings. We aimed to investigate the metastatic rate of IMNs and to provide recommendations on target volume delineation of IMNs for adjuvant radiotherapy in breast cancer patients.MethodsWe retrospectively analyzed data from 114 breast cancer patients treated with surgery without adjuvant radiotherapy who developed local and/or regional lymph node recurrence/metastasis at our institute from January 2015 to January 2019. Patients with widely lung or pleural metastases were excluded. We first analyzed the recurrence rate with the chest wall, the metastatic rate of internal mammary/anterior mediastinal, ipsilateral axillary and supraclavicular lymph nodes, and then investigated the distribution of the IMNs.ResultsAmong the 114 included patients, the recurrence rate with the chest wall, metastatic rate of IMNs, IMNs/anterior mediastinal lymph nodes, ipsilateral axillary lymph nodes, and the ipsilateral supraclavicular lymph nodes was 43, 37.7, 59.6, 12.3, and 22.8%, respectively. The metastatic IMNs were mainly located from the first to the second intercostal space. However, metastatic lymph nodes could also be observed above the upper edge of the first rib.ConclusionsThe metastatic rate is high in the IMNs and irradiation of the internal mammary lymphatic chain is required. It is suggested that the upper bound of the internal mammary lymphatic chain should be up to the subclavian vein with a 5-mm margin, thus connecting to the caudal border of supraclavicular clinical target volume in breast cancer patients at high risk of recurrence.
Highlights
There is a discrepancy about the metastatic rate of internal mammary lymph nodes (IMNs) between clinical and pathologic findings
The definition of lymph node metastasis include that the internal mammary lymph nodes whose short diameter is more than 6 mm, or the lymph node is tightly connected to the internal mammary blood vessels regardless of the short diameter, lymph node who meet one of the above conditions can be seen as metastatic lymph node; the anterior mediastinal lymph nodes whose short diameter were more than 10 mm, or the lymph node is tightly connected to the blood vessels, or lymph node with ring-enhancement in contrast-enhanced Computed Tomography (CT) images can be seen as metastatic lymph node; and the hypermetabolism in PET-CT be diagnosed as metastases even if the short diameter was less than 6 mm or 10 mm [12]
The patients enrolled didn’t undergo postoperative adjuvant radiotherapy owing to various reasons such as lack of indications of radiation therapy, poor economic conditions and so on, but most of the previous studies enrolled patients that underwent postoperative radiotherapy which may reduce the metastatic rate; secondly, the reason is perhaps that nearly 30% of the patients studied underwent PET-CT examination which could improve the detection rate of metastatic lymph nodes probably; and thirdly, in our opinion, the internal mammary lymph node region and the anterior mediastinal lymph node region can be seen as an entirety, so when the metastasis of the anterior mediastinal lymph node occures, we
Summary
There is a discrepancy about the metastatic rate of internal mammary lymph nodes (IMNs) between clinical and pathologic findings. We aimed to investigate the metastatic rate of IMNs and to provide recommendations on target volume delineation of IMNs for adjuvant radiotherapy in breast cancer patients. Based on results from two clinical trials (MA. and EORTC 22922/ 10925) [3, 4], the 2016 National Comprehensive Cancer Network (NCCN) guidelines strongly recommend irradiation of internal mammary lymph nodes (IMNs) in patients with 1–3 positive axillary lymph nodes (ALNs). (category 2A), following mastectomy and lumpectomy [5] This approach is recommended in addition to irradiation of the chest wall and supraclavicular lymph nodes in postoperative adjuvant radiotherapy. The metastatic rate of IMNs was 33% after the extended mastectomy in breast cancer
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