Does a more thorough analysis of the lymph nodes improve survival?

This study evaluated the outcomes of patients with colon cancer (cancer of the large intestine) who underwent a procedure called sentinel lymph node microscopic analysis.

The lymphatic system is composed of lymphatic vessels and lymph nodes which drain the lymphatic fluid, and specialized cells of the immune system. Through the lymphatic system, cancer cells can spread to different organs of the body creating metastases. The first lymph nodes through which cancer cells spread are called sentinel nodes (SN). In order to identify SN, a blue dye is injected into the tumor area and will stain the lymphatic drainage of the tumor. These stained nodes will then be easier to spot during surgery and will be removed and analyzed under a microscope for cancer cells. The early detection of SN is of great importance because it influences the treatment choices and cancer staging as well as the prognosis, recurrence and survival of the patient.

The study included 165 patients with colon cancer who underwent a tumor resection (surgical removal). Of these, 55 underwent a SN procedure and 110 patients did not undergo a SN procedure and were the control group. After surgery, lymph nodes removed from all patients (in both the SN and the control group) were analyzed through a microscope. Patients who were found to have lymph node metastases at the first pathologic analysis underwent additional (adjuvant) chemotherapy. If the result of this first analysis was negative (no metastases were found or node-negative), only the SN group was further examined. Patients were monitored throughout a period of 5 years by physical examination, testing for elevated blood levels of cancer markers and imaging techniques. 

Results showed that using in-depth analysis of the SN raised the accuracy of the standard lymph node evaluation up to 98% and upstaged the cancer in 4 patients. There was a significantly higher 5 year overall survival (the percentage of patients that were alive 5 years after the procedure) in the SN group compared to the control group (83% versus 69%). When only node-negative patients were considered, overall survival was even higher in the SN group (92%) compared with 76% in the control group. Also, disease-free survival (the percentage of patients who survived free of the disease 5 years after the procedure) was significantly higher in the SN group (94%) compared to the control group (77%). Furthermore, cancer specific mortality (the percentage of patients who died because of the cancer) was reduced to 0% in the SN group versus 8% in the control group.

In summary, this study showed that a thorough SN microscopic analysis has an important prognostic impact on patients with colon cancer. The relevance of a more thorough investigation lies in the ability of this procedure to detect hidden metastases and treat them in an early stage with adjuvant chemotherapy.