Occult Axillary Micrometastases Fail to Predict Breast Cancer Survival Outcomes

SAN FRANCISCO—In patients with breast cancer, sentinel lymph node mapping enables a detailed pathologic examination of nodal tissue by multilevel microsections with standard hematoxylin and eosin staining (H&E) and highly sensitive immunohistochemical (IHC) staining. However, the significance of IHC metastases remains unknown.

At the 37th Annual Meeting of the American Society of Clinical Oncology (ASCO abstract 91), Nora M. Hansen, MD, of the John Wayne Cancer Center, Santa Monica, California, presented results of a prospective study showing that a positive finding by IHC staining does not predict poorer overall survival.

Between 1992 and 1999, 683 patients in the trial underwent lymphatic mapping using blue dye with or without radioactive colloid. The sentinel node was examined by both H&E and IHC staining. A total of 603 patients were available for evaluation.

Four Groups

Patients were stratified into four groups based on their sentinel node metastases status.

The negative sentinel node group had 419 patients (group 1). Positive sentinel nodes were found in 264 patients. Of these patients, 56 patients had IHC-positive/H&E negative metastases (group 2). Sentinel node H&E micrometastases (2 mm or less) were found in 76 patients (group 3) and sentinel node H&E macrometastases (greater than 2 mm) in 132 patients (group 4).

Five-year disease-free survival and overall survival were estimated for each group. At a median follow-up of 44 months, the size of sentinel node metastases was a significant predictor of disease-free survival (

P

= .0001) and overall survival (

P

= .0036). There was no significant difference in disease-free or overall survival between sentinel-node-negative patients an sentinel-node IHC-positive patients.

"Micrometastases did not adversely affect survival in this group of patients who underwent sentinel node biopsy," Dr. Hansen said. "We conclude that IHC metastases do not appear to adversely affect prognosis at this time."

She noted that treatment decisions are being made based on IHC results, and it is unclear whether these decisions affect disease-free and overall survival.

"These results suggest that IHC should not be routinely performed on the sentinel node, nor should treatment decisions be made based on IHC findings until results of long-term multicenter trials are reported," Dr. Hansen concluded.