Abstract: Objective To investigate the relationship of lymph node metastasis rate (LNR) with prognosis of esophageal squamous cell carcinoma after radical resection and postoperative adjuvant chemotherapy. Methods The retrospective case-control study was conducted. The clinicopathological data of 121 patients who underwent radical resection of esophageal squamous cell carcinoma in the Peking University Cancer Hospital from January 2012 to September 2016 were collected. There were 105 males and 16 females, aged from 42 to 76 years, with a median age of 58 years. All patients underwent radical resection of esophageal cancer with at least two-field lymph nodes dissection. Some patients underwent corresponding chemotherapy and radiotherapy. The thoracic and abdominal lymph nodes were grouped according to the 7th edition standard of American Joint Committee on Cancer (AJCC). The lymph nodes dissected were labeled in groups, and all the lymph nodes were examined by pathology test. Observation indicators: (1) follow-up; (2) effects of LNR on prognosis of patients in different AJCC N staging; (3) relationship between LNR and postoperative adjuvant chemotherapy. Follow-up was conducted by outpatient examination, telephone interview and hospital statistical office to detect postoperative survival of patients up to February 2017. The disease-free survival time was from surgery date to date of confirmation of tumor recurrence, and the overall survival time was from surgery date to death of the patient or the last follow-up date. Measurement data with skewed distribution were expressed by M (range). The Kaplan-Meier method was used to calculate the survival rate and draw the survival curve. The Log-rank test was used for survival analysis. Results (1) Follow-up: 121 patients were followed up for 3.0-94.2 months, with a median follow-up time of 27.1 months. During the follow-up, 98 of 121 patients had tumor recurrence and metastasis (including 64 deaths), 22 had no metastasis, and 1 had unknown tumor metastasis. The mean overall survival time of patients was 30.8 months. The 1-, 3-, 5-year disease-free survival rates were 47.1%, 20.3%, and 5.9%, respectively. The 1-, 3-, 5-year overall survival rates were 93.1%, 48.7%, and 35.3%, respectively. (2) Effects of LNR on prognosis of patients in different AJCC N staging: of 121 patients, 46 were in N0 stage, 42 were in N1 stage, 28 were in N2 stage, and 5 were in N3 stage. Of 42 patients in N1 stage, 35 with 0 < LNR ≤ 0.15 had a disease-free survival time of 12.2 months (range, 1.2-82.3 months), and 7 with LNR > 0.15 had a disease-free survival time of 6.9 months (range, 2.1-23.1 months); the difference between the two groups was statistically significant (χ2=3.888, P<0.05). Of the 28 patients in N2 stage, 12 with 0 < LNR ≤ 0.15 had a disease-free survival time of 8.5 months (range, 1.2-38.8 months), and 16 with LNR > 0.15 had a disease-free survival time of 4.4 months (range, 1.0-52.7 months); the difference was not statistically significant (χ2=0.007, P>0.05). Forty-six patients in N0 stage were detected no lymph node metastasis, and only 5 cases were in N3 stage, with no analysis. (3) Relationship between LNR and postoperative adjuvant chemotherapy: of the 121 patients, 56 underwent postoperative adjuvant chemotherapy, which was mainly constituted by paclitaxel, platinum, and 5-fluorouracil-based regimens, 58 didn′t undergo postoperative adjuvant chemotherapy, and 7 had unknown data of postoperative adjuvant chemotherapy. Of 121 patients, 46 had LNR = 0, 47 had 0 < LNR ≤ 0.15, 28 had LNR > 0.15. Of the 46 patients with LNR = 0, 17 who underwent postoperative adjuvant chemotherapy had a disease-free survival time of 8.1 months (range, 3.9-66.7 months) and a overall survival time of 34.0 months (range, 4.7-76.0 months); 29 who didn′t undergo postoperative adjuvant chemotherapy had a disease-free survival time of 18.8 months (range, 1.6-53.2 months), and a overall survival time of 48.6 months (range, 8.3-94.2 months); there was no significant difference in the disease-free survival time and overall survival time between the two groups (χ2=0.311, 0.858, P>0.05). Of the 47 patients with 0 < LNR ≤ 0.15, 27 who underwent postoperative adjuvant chemotherapy had a disease-free survival time of 13.3 months (range, 5.0-82.3 months), and a overall survival time of 53.1 months (range, 5.7-82.3 months); 20 without postoperative adjuvant chemotherapy had a disease-free survival time of 8.4 months (range, 1.2-39.2 months), and a overall survival time of 26.5 months (range, 5.9-52.6 months). There were significant differences in the disease-free survival time and overall survival time between the two groups (χ2=10.322, 4.971, P<0.05). Of the 28 patients with LNR > 0.15 (7 had unknown data of postoperative adjuvant chemotherapy), 12 who underwent adjuvant chemotherapy had a disease-free survival time of 10.3 months (range, 2.9-52.7 months), and a overall survival time of 29.5 months (range, 11.2-58.5 months); 9 without postoperative adjuvant chemotherapy had a disease-free survival time of 2.9 months (range, 1.4-35.7 months), and a overall survival time of 14.5 months (range, 3.0-62.3 months); there was a significant difference in the disease-free survival time between the two groups (χ2=6.687, P<0.05), and no significant difference in the overall survival time between the two groups (χ2=2.938, P>0.05). Conclusion LNR can be used as a supplementation of AJCC N staging system. In patients with 0< LNR ≤ 0.15, postoperative adjuvant chemotherapy can improve disease-free survival time and overall survival time.