The impact on post-surgical treatment of sentinel lymph node biopsy of internal mammary lymph nodes in patients with breast cancer

Background: Since the introduction of the sentinel lymph node (SLN) biopsy in breast cancer patients there is a renewed interest in lymphatic drainage to the internal mammary (IM) chain nodes. We evaluated the frequency of lymphatic drainage to the IM chain, the rate of SLNs that contain metastases and the clinical implications of IM LN metastases. Methods: Between June 1999 and April 2005 506 consecutive patients underwent SLN biopsy as a staging procedure for clinically T1-2N0 breast cancer. In all patients preoperative lymphoscintigraphy was combined with the intraoperative use of a gammaprobe. In patients with IM SLNs visualized on lymphoscintigraphy, LNs were extirpated through an intercostal parasternal incision. Results: SLNs were visualized by preoperative lymphoscintigraphy in 99% of all patients (502/506): axillary SLNs in 499 patients (99%), ipsilateral IM LNs in 109 patients (22%). In 85 patients with visualized IM SLNs the IM nodes could be removed (78%). In 20 of the latter 85 patients IM SLNs contained metastases (24%). IM metastases were associated with axillary LN metastases (P < 0.001). In 17 patients IM metastases led to extension of the radiotherapy field, while additional (adjuvant) systemic therapy was given in six patients. COnclusion: SLNs in the IM chain are common in breast cancer patients and can be extirpated in the majority of these patients. The proportion of patients in whom radiotherapeutic treatment was adjusted due to IM LN metastases was substantial. We advocate retrieval of IM SLNs when visualized by preoperative lymphoscintigraphy.