Absence of lymph nodes in the resected specimen after radical surgery for distal rectal cancer and neoadjuvant chemoradiation therapy: what does it mean?

PURPOSE: The number of retrieved lymph nodes during radical surgery has been considered of great importance to ensure adequate staging and radical resection. However, this finding may not be applicable after neoadjuvant therapy in which, not only is there a decrease in lymph nodes recovered, but also a subgroup of patients with absence of lymph nodes in the resected specimen.
METHODS: Patients with absence of lymph nodes were compared with patients with ypN0 disease and patients with ypN+ disease.
RESULTS: Thirty-two patients (11 percent) had absence of lymph nodes, 171 patients (61 percent) had ypN0 disease, and 78 patients (28 percent) had ypN+ disease. Patients with absence of lymph nodes had significantly lower ypT status (ypT0-1, 40 vs. 13 percent; P<0.001) and decreased risk of perineural invasion (6 vs. 21 percent; P=0.04) compared with ypN0 patients. Five-year disease-free survival (74 percent) was similar to patients with ypN0 (59 percent; P=0.2), and both were significantly better than patients with ypN+ disease (30 percent; P<0.001).
CONCLUSIONS: Absence of lymph nodes retrieved from the resected specimen is associated with favorable pathologic features (ypT and perineural invasion status) and good disease-free survival rates. In this setting, absence of retrieved lymph nodes may reflect improved response to neoadjuvant chemoradiation therapy rather than inappropriate or suboptimal oncologic radicality.