Abstracts
2002 Digestive Disease Week

# 103142 Abstract ID: 103142 Lymphatic Mapping Combining Blue Dye with Intraoperative Lymphoscintigraphy Improves Detection of Micrometastases in Early Colorectal Cancer.
Dean T Nora, Sukamal Saha, Donald L Morton, Anton J Bilchik, Santa Monica, CA; Flint, MI

Nodal metastasis is the most important prognostic factor for recurrence and survival in early colorectal cancer (CRC). Dye-directed lymphatic mapping (LM) accurately stages early CRC by identifying sentinel nodes (SNs) for focused histopathologic examination. We hypothesized that combining a radioactive tracer with vital blue dye would increase the accuracy of metastatic detection. Dual-agent LM was performed in 32 patients undergoing resection for early-stage CRC. Prior to resection, 1 cc of 1% Lymphazurin(r) and then 500 µCi of technetium sulfur colloid were separately injected around the tumor in the subserosal layer. During LM, SNs were identified by visualization of the blue stain and/or gamma-probe (Navigator(r), US Surgical) detection of radioactivity. All SNs were marked by a suture and the en-bloc surgical specimen was sent for pathologic review. Each SN was examined by multilevel sectioning and immunohistochemical staining; nonsentinel nodes were examined by hematoxylin and eosin staining. The tumor status of the SNs accurately predicted the status of the nodal basin in 29 (90.6%) patients. Eleven (34%) patients had nodal metastasis; 5 (45.5%) were isolated to sentinel nodes (average size 6mm) and 4 (36.3%) were in T1/T2 lesions. Dual-agent LM identified micrometastases in 4 patients (19%) whose nodes were negative by H&E. These micrometastases may have been missed without focused examination. Furthermore, lymphoscintigraphy detected aberrant drainage to the deep iliac and inguinal nodes in one low rectal cancer. There was an average of 2.4 nodes that were blue only as compared to 1.2 that were blue and radioactive (p<0.001). However, the blue and radioactive nodes were more likely to contain metastases (72.7% versus 27.3%; p=0.025). These data demonstrate that dual-agent LM increases the likelihood of identifying micrometastases and tumor deposits in small lymph nodes. Dual-agent LM may be the most sensitive method to detect nodal involvement in early stage CRC.