Sentinel Lymph Node Mapping and Analysis in Colon Cancer Using Indocyanine Green Dye

Intra-operative Sentinel Lymph Node Mapping Using Indocyanine Green Dye Near-infrared Fluorescence Imaging in Colon Cancer: Prospective Single Center Study

Approximately 20-30 % of colon cancer patients who have no metastasis in lymph nodes after definitive colectomy have recurrence with distant metastasis. These recurrences could be due to missed occult tumor cells or micrometastasis. Detailed examination of all lymph nodes is expensive and time consuming. Sentinel lymph node mapping using Indocyanine green dye helps in identifying the lymph nodes which are most likely to harbour metastasis. These sentinel lymph nodes can be subsequently subjected to detailed pathologic examination and immunohistochemistry which increases the likelihood of identifying micrometastasis and occult tumor cells. Patients found to harbour such metastasis can be treated with additional chemotherapy after surgery. The aim of the study is to examine the feasibility of sentinel lymph node mapping using Indocyanine green dye in colon cancer and evaluate the upstaging rate in post-operative colon cancer patients who don't have metastatic lymph nodes on routine histopathology.

All patients of colon cancer fulfilling the inclusion criteria and excluding the patients according to the exclusion criteria will undergo standard laparoscopic/open colectomy. Indocyanine green dye is injected around the tumor in subserosal location for open surgeries and submucosally after on-table colonoscopy for laparoscopic surgeries and followed with near-infrared scope. Patients will undergo intra-operative on-table colonoscopy after induction of anesthesia. All sentinel nodes will be marked with clips/sutures for identification by the pathologist post-operatively. Any aberrant lymph nodes identified outside the planned resection margins will be excised, marked with the position of excision and sent separately from the gross specimen. After this the surgeon will proceed with the surgery including vascular ligation and resection of mesocolon. After surgery, all the lymph nodes identified in the specimen including the tagged sentinel lymph nodes will be examined using standard Hematoxylin and eosin staining. If all the lymph nodes are negative for metastasis, the sentinel lymph nodes will undergo additional stepwise sections and immunohistochemistry for pancytokeratin.

Sentinel lymph node mapping: 25 mg of Indocyanine green dye diluted in 1 ml of 20% Albumin solution and 9 ml of 0.9% Normal saline solution will be used. Injections (0.5-1 ml) will be given in the submucosa or subserosa at 2-4 points around the tumor proximally and distally. Lymphatic flow will be followed after injection in real time with Near-infrared fluorescence imaging scope until sentinel lymph nodes will be identified.

The pathologist involved in routine histological assessment of the resected lymph nodes including lymph nodes in the gross specimen and sentinel lymph nodes will be blinded to the identity of the sentinel lymph nodes.

Indocyanine green dye is injected in the submucosa or subserosa around the tumor to identify sentinel lymph nodes intra-operatively with near infrared fluorescence imaging.

Through on-table colonoscopy indocyanine green solution will be injected in the submucosa at 2-4 points around the tumor for laparoscopic surgeries. Dye will be injected in the subserosa at 2-4 points for open surgeries. Lymphatic flow from the tumor will be mapped in real time with near-infrared fluorescence imaging scope and sentinel lymph nodes will be identified.

Proportion of the number of successful sentinel lymph node procedures out of all executed sentinel lymph node procedures.

Sentinel lymph nodes in patients are pathologically node negative on routine evaluation with undergo detailed evaluation using serial sections and immunohistochemistry to identify micrometastasis and occult tumor cells. The proportion of node negative patients who are upstaged will be calculated.

No of patients with successful sentinel lymph node mapping - False negatives/ No of patients with successful sentinel lymph node mapping.

number of patients in whom a negative sentinel lymph node correctly predicted the lymph node status of the total lymph node yield.

proportion of sentinel lymph nodes identified outside planned resection margins and their tumor bearing status .

Inclusion criteria: Age 18 years or older Biopsy proven colon cancer Scheduled for laparoscopic/open colectomy Exclusion criteria: Prior colorectal surgery Gross lymph node invasion on pre-operative imaging or intraoperative staging Advanced disease (T4 disease or metastasis) on preoperative imaging or intraoperative staging Allergy to iodide containing compounds, human albumin or Indocyanine green dye History of hyperthyroidism or thyroid adenoma Palliative surgery Advanced hepatic failure Advanced renal failure