Optimal prognostic lymph node staging system for gallbladder adenocarcinoma: A multi-institutional study.

Abstract

364 Background: The American Joint Committee on Cancer (AJCC) classification is the most universally accepted lymph node (LN) staging system for gallbladder adenocarcinoma (GBA); however, it focuses more on location of LN metastasis than number of LN metastasis. Other lymph node staging systems have been proposed for GBA. We therefore sought to examine the performance of different staging systems including AJCC LN staging system, number of metastatic LN (NMLN), log odds of metastatic LN (LODDS), and LN ratio (LNR). Methods: Patients who underwent curative-intent resection for GBA between 2000 and 2015 and who had lymphadenectomy were identified from a multi-institutional database. The prognostic performance of four staging systems was compared by Harrell’s C and Akaike information criterion (AIC). Results: Overall 214 patients with a median age of 66.7 years (IQR 56.5, 73.1) were identified. A total 1,334 LNs were retrieved from 214 patients, with a median of 4 (IQR 2-8) LNs per patient. In the study cohort, 98 (45.5%) patients had LN metastasis with total of 271 positive LNs [median of 1 (IQR 1-3)]. Patients with LN metastasis had an increased risk of death (HR 1.87, 95%CI 1.24-2.82; P = 0.003). In addition, risk of death increased by each additional LN metastasis (HR 1.20, 95%CI 1.06-1.37; P = 0.005). In the entire cohort, LNR, in either a continuous (C-index: 0.603, AIC: 808.4) or a discrete scale (C-index 0.609, AIC 802.2), provided better discrimination versus LODDS, AJCC LN staging system, and NMLN. The relative performance of all scoring systems was better among patients who had ≥ 4 LN examined. In the cohort of patients with ≥ 4 LN examined, LODDS (C-index 0.621, AIC 363.8) had the best performance compared with LNR (C-index 0.615, AIC 368.7), AJCC LN staging system (C-index 0.601, AIC 373.4), and NMLN (C-index 0.613, AIC 369.5). Conclusions: LODDS and LNR performed better than the AJCC LN staging system. Among those who had more LN examined, LODDS performed better than LNR. LODDS and LNR should be incorporated into the AJCC LN staging system of GBA.