Association of lymph node count and overall survival in node-negative endometrial cancers

Purpose To estimate whether the number of lymph nodes removed during surgery is associated with overall survival among women with endometrial cancer. Methods We performed a retrospective cohort study of women with node-negative, stage I to IIIB endometrial cancer (n = 152,702) identified from the 1998-2011 National Cancer Database. Multivariable Cox proportional hazards regression tested for an association of lymph node count with survival. Restricted mean survival and relative hazard curves were plotted for survival as a function of number of removed lymph nodes. ResultsAmongwomenwith node-negative endometrioid endometrial cancer, for each additional five lymph nodes removed, the hazard for death decreased: stage I, the hazard ratio (HR) was 0.95 (95% CI, 0.93 to 0.97; P < .001), stage II, HRwas 0.90 (95% CI, 0.87 to 0.94; P < .001); and stage IIIA-B, HR was 0.92 (95% CI, 0.88 to 0.96; P < .001). When grouped by grade, each additional five lymph nodes removed was also associated with decreased hazard for death: grade 1, HR was 0.96 (95% CI, 0.93 to 0.99; P = .009); grade 2,HRwas0.91(95%CI, 0.89 to 0.94;P < .001); and grade 3,HRwas 0.95(95%CI, 0.92 to 0.97;P < .001). Increased lymph node dissection was also associated with increased survival among women with nodenegative stage II (HR, 0.92; 95% CI, 0.86 to 0.98; P = .01) or stage IIIA-B (HR, 0.94; 95% CI, 0.89 to 0.99; P = .025) uterine serous carcinoma, but not among women with carcinosarcoma or clear cell adenocarcinoma. Five-year survival for women with one to four nodes removed and endometrioid or serous histology was 85% (95% CI, 84% to 85%) and 54% (95% CI, 50% to 59%), respectively. Five-year survival was significantly higher for women with ≥ 20 removed nodes and endometrioid (91%; 95% CI, 90% to 91%) or serous (72%; 95% CI, 68% to 76%) histology (P < .001). Conclusion Increased lymph node count is associated with a 1% to 14% decreased hazard of death per each additional five lymph nodes removed and a 5%to 20% increased 5-year survival among women with pathologically node-negative endometrioid and serous endometrial cancers.