Probe-guided surgery for colorectal cancer

Anti-CEA-scintigraphy turned out to be very reliable in detecting primary and recurrent colorectal cancer, its overall accuracy being more than 90%. The intraoperative application of this technology should provide similar results when focussing at extrahepatic tumor deposits, for example in lymph nodes, thus allowing accurate staging of the underlying disease. To test this hypothesis we launched the following feasibility study the results of which are compared to those reported in the recent literature. We investigated 20 patients, six with rectum and 14 with colon cancer. 24 hours before surgery they were intravenously given 1 ml of a fab'-fragment-antibody to CEA, labeled with 25 mCi of 99mTc (CEA-Scan). During surgery the radioactivity in lymph glands regional to the tumors was measured and compared to the much lower activity in healthy nodes. For this we used a scintillation probe (C-Trak, Care Wise, Inc., Morgan Hill, CA). All lymph nodes of interest were then excised and submitted to frozen section pathology. In 7 out of 20 cases scintimetry led to an up-staging of the disease. In addition we found metastatic spread to lymph nodes that were basically not regional to the primary tumor (retroperitoneum, renal hilum etc.). Scintimetry can precisely identify even very small tumor deposits. So it leads to accurate staging while surgery is still ongoing. In a further step the concept of sentinel node diagnosis, which is right now being clinically evaluated, may some day be applied in colorectal surgical oncology.