Molecular staging of early colon cancer on the basis of sentinel node analysis: A multicenter phase II trial

Purpose: Approximately 30% of patients with American Joint Committee on Can cer stage I or II colorectal cancer (CRC) develop systemic disease. We hypo thesized that multimarker reverse transcriptase-polymerase chain reaction ( RT-PCR) analysis of sentinel lymph nodes (SNs) draining a primary CRC could detect micrometastases not detected by conventional histopathologic analys is. Patients and Methods: In a multi-institutional study, 40 patients with prim ary CRC underwent dye-directed lymphatic mapping at the time of colon resec tion. Each dye-stained SN was tagged, and the tumor and regional nodes were resected en bloc. All lymph nodes were examined by conventional hematoxyli n and eosin (HE) staining. In addition, each SN was cut into multiple secti ons for cytokeratin immunohistochemical (CK-IHC) staining and for RT-PCR an d electrochemiluminescent detection of three markers: beta -chain human cho rionic gonadotropin, hepatocyte growth factor receptor, and universal melan oma-associated antigen. Whenever possible, RT-PCR assay was also performed on primary tumor tissue. The detection sensitivity of individual markers wa s 10(-3) to 10(-4) mug of RNA and one to five tumor cells in 10(7) lymphocy tes of healthy donors. Results: One to three SNs were identified in each patient. An average of 15 nodes were removed from each CRC specimen. No nonsentinel (untagged) node contained evidence of tumor if all tagged (sentinel) nodes in the same spec imen were histopathology tumor-negative. HE staining of SNs identified tumo r in 10 patients (25%), and CK-IHC of SNs identified occult micrometastases in four patients (10%) whose SNs were negative by HE. Of the remaining 26 patients with no evidence of SN involvement by HE or CK-IHC, 12 (46%) had p ositive RT-PCR results. The number of markers expressed in each SN correlat ed (P < .04) with the T stage of the primary tumor. There war 79% concordan ce in marker expression for the respective pairs (n = 38) of primary tumor and histopathologically positive SNs, and 86% (12 of 14) concordance betwee n RT-PCR positive and histopathologically positive SNs. Conclusion: Identification and focused examination of the SN is a novel met hod of staging CRC. CK-IHC and RT-PCR identified occult micrometastases in 53% of patients whose SNs were negative by conventional staging techniques. These ultrasensitive assays of the SN can identify patients who may be at high risk for recurrence of CRC and therefore are more likely to benefit fr om systemic adjuvant therapy.