Application of intraoperative ultrasound to nonsentinel node assessment in primary breast cancer.

Purpose: To evaluate whether intraoperative ultrasonography can help surgeons to identify patients with breast cancer and metastases confined to the sentinel node.
Experimental Design: We used blue dye to identify sentinel node during 512 procedures done on 509 patients with breast cancers of <3 cm. After sentinel node biopsy, we used intraoperative ultrasonography to explore the whole axilla followed by at least level II axillary dissection. All sentinel nodes were evaluated histologically and immunohistochemically using anti-cytokeratin antibody. All nonsentinel nodes were examined by routine histology. Multiple logistic regression was used to assess the associations of interest and to adjust for potential confounders. Receiver operating characteristic curves were used to calculate the areas under the curves of interest and for comparisons.
Results: Sentinel nodes were identified in 506 of 512 (98.8%) procedures and sentinel node metastases were found in 161 of these (31.8%). Subsequent axillary dissection revealed tumor involvement in nonsentinel nodes in 93 of 161 (57.8%) procedures. Multivariate analysis showed that tumor size, number of positive sentinel nodes, and metastatic size in sentinel nodes were independent factors predicting the presence of tumor-positive nonsentinel nodes. The validity of using either node size or cortical thickness ascertained by intraoperative ultrasound to predict nonsentinel node metastases was highly significant (P < 0.0001). Intraoperative ultrasound not only detected metastatic nonsentinel nodes in 89 of 93 (95.7%) cases but also detected metastatic nonsentinel nodes in patients with false-negative sentinel node mapping.
Conclusion: Sentinel node biopsy combined with intraoperative ultrasonography can help breast surgeons decide whether to perform a subsequent nonsentinel node dissection after identification of a positive sentinel node.