Validation of a nomogram to predict the risk of nonsentinel lymph node metastases in breast cancer patients with a positive sentinel node biopsy: validation of the MSKCC breast nomogram.

Background: Completion axillary lymph node dissection (ALND) remains the standard of care for patients with disease-positive sentinel lymph nodes (SLN). However, approximately two-thirds will have no additional disease-positive nodes. To identify the patient's individual risk for non-SLN metastases, the Memorial Sloan-Kettering Cancer Center (MSKCC) developed a nomogram.
Methods: The records of 182 breast cancer patients who underwent SLN and ALND were selected. Serial hematoxylin and eosin (HE) analysis and immunohistochemistry were routinely performed on each sentinel node. For application of the nomogram, the detection method was assigned in two ways: for all metastases visible by serial HE, the method of detection was scored as "serial HE" (method 1), independent of the tumor size, and by a combination of size and staining method (method 2); so macrometastasis were scored as detected by routine HE, micrometastasis by serial HE, and isolated tumor cells by immunohistochemistry. A receiver operating characteristic curve (ROC) was drawn, and the area under the curve was calculated to assess the discriminative power of the nomogram.
Results: The area under the ROC was .71 (range, .64-.79) according to method 1 and .75 (range, .67-.88) according to method 2.
Conclusions: Because the variable "method of detection" in the MSKCC nomogram is a surrogate for SLN metastasis size, the size category of the SLN metastasis can be used in applying the nomogram to patients in whom the SLN histologic analysis is performed by a much different procedure than that used to develop the MSKCC nomogram. This results in an improved predictive accuracy.