The Effects of Preoperative Chemoradiotherapy on Lymph Node Sampling in Rectal Cancer

BACKGROUND: The current recommendation from the American Joint Committee on Cancer and the International Union Against Cancer is that 12 or more lymph nodes should be examined to appropriately stage rectal cancer. It is unclear if this metric is appropriate or achievable for patients who receive neoadjuvant therapy. OBJECTIVE: The purpose of this study was to review the effects of neoadjuvant chemoradiotherapy on the lymph node yield in patients with rectal cancer. DATA SOURCES: A comprehensive search was made of MEDLINE, PubMed, and Web of Science for articles published through December 2011. STUDY SELECTION: The descriptors rectal neoplasms, lymph nodes, lymph node yield, radiotherapy, and neoadjuvant therapy were used to identify articles that reported the lymph node yield with and without neoadjuvant chemoradiotherapy for rectal cancer. INTERVENTIONS: Patients received either chemoradiotherapy or no neoadjuvant treatment before undergoing total mesorectal excision for rectal cancer. MAIN OUTCOME MEASURES: The main outcome measures included the mean lymph node yield both with and without neoadjuvant treatment, the percentage of patients that received an adequate lymph node dissection, and the number of lymph nodes found to be positive for metastatic disease. RESULTS: A total of 7 studies were included in this review. They demonstrated a decrease in lymph node yield in patients who received neoadjuvant therapy, ranging from 7% to 53% based on the articles in this review. LIMITATIONS: A meta-analysis was not performed because of the limited complete data published on this subject. Consequently, there is heterogeneity in the studies that were selected for this review. CONCLUSIONS: Patients with rectal cancer who receive preoperative chemoradiotherapy should be anticipated to have a lower lymph node yield than patients who receive surgery alone. This calls into question if the current guideline of 12 lymph nodes is relevant, in particular, for those patients receiving neoadjuvant therapy.