Understanding the factors associated with reduction in the number of lymph nodes in rectal cancer patients treated by neoadjuvant treatment

Rectal cancer patients frequently present with locally advanced disease for which the standard of care includes neoadjuvant chemoradiotherapy followed by total mesorectal excision. Positive lymph nodes are one of the most powerful risk factors for recurrence and survival in colorectal cancer. In the absence of specific rectal guidelines, the literature recommends to the pathologist to optimize the number of rectal lymph nodes (LN) retrieved. We made a literature review in order to identify factors that could potentially affect the number of LN retrieved in specimens of patients with rectal cancer treated by chemoradiotherapy (CRT) followed by total mesorectal excision (TME).Age did not have a significant effect on LN yield. The effect of sex on LN number is not consistent in the literature. Most of the papers did not find a relationship between lower LN obtained and gender. Laparoscopy for primary rectal cancer is associated with a greater number of LN as well as short-term benefits. Tumors in the upper rectum are associated with a higher number of LN than those in the mid and lower rectum. The type of surgery had no effect on lymph node yield either. Tumors with complete or almost complete pathologic regression were exactly the ones with lower number of lymph nodes detected. Approximately one-third of patients with neoadjuvant treatment had less than 12 LN yield.The tumor regression grade is the most important factor for the decrease in the number of lymph nodes.