UICC World Cancer Congress 2006

Objectives: To review the present status of the use of sentinel node mapping in treating gastrointestinal tract cancer. Methods: The Ovid Medline system was used to identify all English language papers with the keywords, sentinel lymph node and esophageal/gastric/colorectal neoplasms published between 1996 and 2006. After excluding animal studies or recurrent tumors, comments or letters to Editor, case reports and several overlapping papers, 9 papers on esophageal cancer, 23 on gastric cancer and 45 on colo-rectal cancer were identified. In this review we focus on gastric and colo-rectal cancer. Results: 1) Gastric cancer In gastric cancer, SN mapping (M) and SN navigation surgery (NS) is not yet established and remained an experimental procedure. In gastric cancer, accurate staging by SN mapping may allow surgeons to avoid unnecessary lymphadenectomy and consequently an unnecessary gastrectomy in cases of T1 tumors. QOL after gastrectomy is mostly related to gastric resection and not the lymph node dissection as observed in breast cancer. Unlike colorectal cancer, the studies of SNM or SNNS in gastric cancer are not aimed at the selection of candidates for post-operative adjuvant therapy. Only one RCT of small sample size was carried out to validate SNM. This study was negative study showing high false negative rate. A learning curve appears to exist with both the radio-isotope and dye technique. The most frequently used dyes are isofulfan blue or indocyanine green. The radio active colloid used is usually 99m-Technetium tin colloid. Two large sized prospective studies to evaluate the validity of SNM in gastric cancer are on going in Japan. 2) Colo-rectal cancer In colon cancer, preservation of the bowel is not really beneficial for patients. When a segment of colon is resected, the procedure with or without mesentery where most of regional nodes exists, makes little difference in QOL, due to simple anatomical structure of the organ. In this regard, SNM may have surgical importance in small rectal cancers. If a wedge resection with enough of a margin could replace a low or super-low anterior resection, QOL of the patients would be much improved. However, few studies have been published studies on rectal cancer. The majority are aimed at the selection of candidates for post-operative adjuvant therapy and no to avoid unnecessary lymphadenectomy. This concept of SNM is rather unique to this cancer due to the fact that post-operative adjuvant chemotherapy can improve remarkably the survival in node positive but not so much in node negative patients. In the Western practice, pathologists do not retrieve all the lymph nodes, especially when they are small. The average number of examined lymph nodes is modest and might cause stage migration. To improve this situation, SNM may be useful but macroscopic metastatic nodes accompanying occlusion of perinodal lymph vessels are not detected by SNM and thus may lead to false negativity. 3) SNNS requires diagnosis during surgery Unlike breast cancer or skin cancer, second surgery of regional lymph nodes is not realistic in GI tract cancers. Therefore exact diagnosis during surgery is mandatory. However, how to handle lymph nodes during surgery is not yet well established in these cancers. 4) Isolated tumor cells (ITC) and micrometastasis (MM) in lymph nodes In UICC TNM classification, ITC and MM are clearly discriminated. Clinical relevance or prognostic impact of ITC is controversial, suggesting that most of ITC would not evolve into metastasis. MM seems clinically different from ITC but no study has been carried out to compare them. Although ITC and MM cannot be distinguished by RT-PCR, it is possible to select patients who do not have any cancer cells in lymph nodes by RT-PCR using whole material of lymph nodes. However, if whole material is used for this examination, no one can know if there was any metastasis in lymph nodes diagnosed by histological examination. Summary: The clinical role of SNM and SNNS is not yet established in either colo-rectal or gastric cancer. As the benefit of SNNS seems large in T1 gastric cancer, the results of on-going studies are awaited.