Number of lymph nodes examined and prognosis among pathologically lymph node-negative patients after preoperative chemoradiation therapy for rectal adenocarcinoma

BACKGROUND: Preoperative chemoradiation for rectal cancer can decrease the number of evaluable lymph nodes. Hence, the prognostic role of lymph node evaluation in patients with rectal cancer who receive preoperative chemoradiation is unclear. The authors of this report evaluated the prognostic impact of the number of lymph nodes examined in patients with rectal cancer who had negative lymph nodes based on the pathologic extent of disease (ypN0) after they received preoperative chemoradiation. METHODS: Between 1990 and 2004, 372 patients with nonmetastatic rectal adenocarcinoma received preoperative chemoradiation followed by mesorectal excision and had ypN0 disease. The median radiation dose was 45 gray, and 68% of patients received adjuvant chemotherapy. RESULTS: Patients had a median of 7 lymph nodes examined after preoperative chemoradiation. Compared with patients who had ≤7 lymph nodes examined, patients who had >7 lymph nodes had higher 5-year rates of freedom from relapse (86% vs 72%; log-rank P =.005) and cancer-specific survival (95% vs 86%; log-rank P =.0004), but no significant difference was observed in the overall survival rate (87% vs 81%; log-rank P =.07). Multivariate Cox proportional models demonstrated that patients who had >7 lymph nodes examined had a significantly lower risk of relapse (hazard ratio [HR], 0.39; P =.003) and death from rectal cancer (HR, 0.45; P =.04) but a similar risk of all-cause mortality (HR, 0.75; 95% CI, 0.46-1.20; P =.23) compared with patients who had a;circ7 lymph nodes examined. CONCLUSIONS: The number of lymph nodes examined was associated independently with disease relapse and cancer-specific survival in patients with rectal cancer who had ypN0 disease after receiving preoperative chemoradiation. Hence, the authors concluded that the number of negative lymph nodes examined may be a prognostic factor in patients with rectal cancer who receive preoperative chemoradiation.