Background: The presence or absence of lymph node metastases is known to be an important prognostic factor for patients with pancreatic cancer. Few studies have investigated the ratio of the number of lymph nodes harboring metastatic cancer to the total number of lymph nodes examined (lymph node ratio [LNR]) with regard to outcome after pancreaticoduodenectomy for ductal cancer of the pancreas. Methods: Between 1995 and 2005, a total of 905 patients underwent pancreaticoduodenectomy for pancreatic adenocarcinoma. Demographics, operative data, number of lymph nodes evaluated, number of lymph nodes with metastatic carcinoma, LNR, pathologic margin status, and long-term survival were analyzed. Results: There were 187 (20.7%) of the 905 patients who had negative peripancreatic lymph nodes (N0), whereas 718 (79.3%) of the 905 patients had lymph node metastases (N1). The median number of lymph nodes evaluated in the N0 group was 15 versus 18 in the N1 group (P = .12). At median follow-up of 24 months, the median survival for all patients was 17.4 months, and the 5-year actuarial survival rate was 16.1%. Patients with lymph node metastases had a shorter median overall survival (16.5 months) compared with patients with negative lymph nodes (25.3 months; P = .001). Compared with the total number of lymph nodes examined or total number of lymph node metastases, LNR was the most compelling predictor of survival. As the LNR increased, median overall survival decreased (LNR = 0, 25.3 months; LNR > 0 to 0.2, 21.7 months; LNR > 0.2 to 0.4, 15.3 months; LNR > 0.4, 12.2 months; P = .001). After adjusting for other factors associated with survival, LNR remained an independent predictor of overall survival (P < .001). Conclusions: After pancreaticoduodenectomy for adenocarcinoma of the pancreas, LNR was one of the most powerful predictors of survival. LNR should be considered when stratifying patients in future clinical trials.
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