Probe-guided surgery for colorectal cancer

Area of Science:

• Oncology
• Nuclear Medicine
• Surgical Oncology

Background:

• Anti-carcinoembryonic antigen (CEA) scintigraphy demonstrates high accuracy (>90%) in detecting primary and recurrent colorectal cancer.
• Intraoperative application of CEA scintigraphy is hypothesized to improve staging by detecting extrahepatic tumor deposits, such as lymph node metastases.

Purpose of the Study:

• To evaluate the feasibility and accuracy of intraoperative anti-CEA scintigraphy for detecting lymph node metastases in colorectal cancer patients.
• To compare the diagnostic performance of intraoperative scintimetry with traditional pathological staging.

Main Methods:

• A feasibility study involving 20 patients (6 rectal, 14 colon cancer) undergoing surgery.
• Patients received intravenous anti-CEA fab'-fragment antibody labeled with 99mTc (CEA-Scan) 24 hours before surgery.
• Radioactivity in regional lymph nodes was measured intraoperatively using a scintillation probe and compared to healthy nodes, followed by excision and frozen section pathology.

Main Results:

• Intraoperative scintimetry led to up-staging of the disease in 7 out of 20 cases.
• Metastatic spread was identified in lymph nodes not considered regional to the primary tumor (e.g., retroperitoneum, renal hilum).
• Scintimetry demonstrated the ability to precisely identify even very small tumor deposits.

Conclusions:

• Intraoperative anti-CEA scintigraphy provides accurate staging of colorectal cancer during surgery.
• This technique enhances the detection of lymph node metastases, including those in non-regional sites.
• Future applications may include sentinel node diagnosis in colorectal surgical oncology.