Paradigm shift of staging and treatment for early breast cancer in the sentinel lymph node era

Lymph node status is the most reliable prognostic indicator for the clinical outcome of patients with most solid cancers. Because it is the first node draining the primary cancer, the sentinel lymph node (SLN) is most likely to harbor metastatic cancer cells. The tumor size of primary breast cancer is highly correlated with SLN metastasis. If the SLN is negative, the negative predictive value of the remaining nodal basin exceeds 95%. It appears that even using different techniques from different institutions, the successful rate to harvest the SLN is more than 95%. The false-negative rate is about 5-10% in most series. Breast cancer patients with early detection and a negative SLN have a significantly improved survival rate. The SLN data in breast cancer is so convincing that SLN information has been incorporated into the new American Joint Committee on Cancer (AJCC) classification of breast cancer. The therapeutic value of additional lymph node dissection after a positive SLN for breast cancer is still controversial. Follow-up data from breast cancer patients is somewhat limited, but available information shows that patients with negative SLNs fare much better. In summary, several important patterns of metastasis can be established based on the current SLN experience: 1) The earlier the breast cancer is found, the less the metastatic potential. 2) In most cases, breast cancer follows an orderly progression of metastasis to the SLN. 3) A small subgroup of patients may develop systemic dissemination without SLN involvement. Since metastatic cancer is usually incurable, it is important for oncologists to detect and resect an early breast cancer without delay. The challenge in the future will be to dissect these different patterns of metastasis based on molecular or genetic markers. Such information will be critical to select high-risk patients for adjuvant therapy.