Biological impact of skip metastasis in patients with gastrointestinal cancers undergoing sentinel lymph node mapping.

Abstract

499 Background: As in melanoma and breast cancers, sentinel lymph node (SLN) mapping has been successfully used in gastrointestinal (GI) cancers (Ca) for accurate nodal staging. However, due to variable incidence of skip metastasis between different parts of the GI tract, its usefulness has been questioned for the proper staging. Hence, we aimed to evaluate the rates of skip mets, its mechanism and its biological impact in GICa. Methods: A search of English literature was performed incorporating MEDLINE and Cochrane library database using the following terms: skip metastasis, sentinel node, colorectal, gastric, and esophageal cancer. The following were excluded: comments, case reports, reviews, fewer than 40 patients in the study. The remaining were used for data extraction. Results: Between 2000-2009, 27 studies including 3,589 patients (122 esophageal, 1,185 gastric, 2,113 colon, and 169 rectal cancers) were reviewed. The overall success rate of SLNM was 95% (96.6% in esophageal, 94% in gastric, 94.3% in colon, and 95.6% in rectal cancer). Nodal positivity (positive SLN and/or non-SLN) was 34% in esophageal, 36.6% in gastric, 48.1% in colon, and 41% in rectal cancers. Rates of skip mets were 18%, 14%, 20%, and 15% in esophageal, gastric, colon, and rectal cancers respectively. In patients with skip mets, T3/T4 disease was found in 65%, 44%, and 82.5% of patients with esophageal, gastric and colon cancers respectively. The average tumor size ranged between 3 cm in gastric to 4.4 cm in colon cancer. The most common primary site for skip mets in colon cancer was the right side (50%), and in LN basin 7, 8, 9 in gastric cancer. All node positive (true and false negative) patients were staged as stage III and were treated with adjuvant chemotherapy. Conclusions: Skip mets are common in T3/T4 disease, and in larger tumors suggesting difficulty injecting the dye circumferentially. All node positive patients (true positive and skip mets) are treated with chemotherapy. Hence, skip mets has no real clinical impact on either the staging, treatment, or the outcome of the disease. No significant financial relationships to disclose.