Survival benefit of lymphadenectomy for gallbladder cancer based on the therapeutic index: An analysis of the US extrahepatic biliary malignancy consortium.

The survival benefit of lymphadenectomy among patients with gallbladder cancer (GBC) remains poorly understood.Patients who underwent resection for GBC between 2000 and 2015 were identified from a US multi-institutional database. The therapeutic index (LNM rate multiplied by 3-year overall survival [OS]) was determined to assess the survival benefit of lymphadenectomy.Among 449 patients, less than half had LNM (N = 183, 40.8%). The median number of evaluated and metastatic lymph nodes (LNs) was 3 (interquartile range [IQR]: 1-6) and 1 (IQR: 0-1), respectively. 3-year OS among patients with LNM in the entire cohort was 26.8%. The therapeutic index was lower among patients with T4 (5.9) or T1 (6.0) tumors as well as carbohydrate antigen (CA19-9) ≥200 UI/mL (6.0). Of note, a therapeutic index difference ≥10 was noted relative to CA19-9 (<200: 18.7 vs ≥200: 6.0), American Joint Committee on Cancer T Stage (T1: 6.0 vs T2: 17.8 vs T4: 5.9) and number of LNs examined (1-2: 6.9 vs ≥6: 16.9). Concomitant common bile duct resection was not associated with a higher therapeutic index among patients with either T2 or T3 disease.Certain clinicopathological factors including T1 or T4 tumor and CA19-9 ≥200 UI/mL were associated with a low therapeutic index. Resection of six or more LNs was associated with a meaningful therapeutic index benefit among patients with LNM.