DETECTION OF OCCULT BREAST-CANCER MICROMETASTASES IN AXILLARY LYMPH-NODES USING A MULTIMARKER REVERSE TRANSCRIPTASE-POLYMERASE CHAIN-REACTION PANEL

Background: Axillary lymph node status in breast cancer patients remai ns the single most important predictor of outcomes. Current methods of histopathologic analysis may be inadequate because 30% of node-negati ve patients recur. The purpose of this study was to test the hypothesi s that a multigene reverse transcriptase-polymerase chain reaction (RT -PCR) panel provides a more sensitive method to detect axillary lymph node metastases than routine pathologic examination. Study Design: Six ty-one consecutive breast cancer patients were evaluated, with nine no rmal control patients. Nodes > 1 cm were bisected for histopathologic and RT-PCR analysis. Nodal tissue was homogenized, and total RNA was c onverted into cDNA with reverse transcriptase. Reverse transcriptase-p olymerase chain reaction analysis was performed with primers specific for keratin-19, c-myc, prolactin inducible protein (PIP), and beta-act in using ethidium bromide gel electrophoresis. Reverse transcriptase-p olymerase chain reaction positive/ pathology negative axillary lymph n odes were reevaluated using step sectioning and immunohistochemical st aining. Results: Thirty-seven patients had pathologically negative axi llary lymph nodes, of which 15 (40%) were positive by RT-PCR analysis. Two RT-PCR negative results tone probably from tissue processing erro r and the other secondary to sampling error) among the 24 histological ly positive specimens were detected (8%). The number of patients in ea ch pathologic stage was 26 patients in stage I; 18, stage IIA; 7, stag e IIB; 7, stage IIIA; 3, stage IIIB; and 0 patients in stage TV. By RT -PCR staging, 8 of 26 patients went from stage I to IIA (30%), and 7 o f 18 from stage IIA to IIB (39%). Of the RT-PCR positive individuals w ho were stage I by pathologic analysis, 100% were found to be c-myc po sitive, 0% keratin-19 positive, and 0% PIP positive; for stage IIIB pa tients these markers were 50%, 100%, and 100% respectively. Additional ly, an increasing number of positive markers per specimen appeared to correlate with larger primary tumor size (p < 0.01) and decreased pred icted 5-year survival (r = 0.950, p < 0.002). Conclusions: Multimarker RT-PCR analysis appears to be a readily available and highly sensitiv e method for the detection of axillary lymph node micrometastases. Lon gterm followup of RT-PCR positive patients will be required to determi ne its clinical relevance. If validated as a predictor of disease recu rrence, this method would provide a powerful complement to routine his topathologic analysis of axillary lymph nodes. (J Am Coil Surg 1998;18 7:9-16. (C) 1998 by the American College of Surgeons).