Validation of American Joint Committee on Cancer eighth staging system for gallbladder cancer and its lymphadenectomy guidelines

Background: For gallbladder cancer (GBC), the American Joint Committee on Cancer eighth edition (AJCC 8) staging system classifies lymph node (LN) stage by the number of positive LN and recommends sampling of ≥6 LNs. We evaluated the prognostic capability of the AJCC 8 for patients undergoing resection and the current national trends in LN staging in the context of these new recommendations for nodal (N) sampling. Methods: Utilizing the National Cancer Data Base, we identified all gallbladder adenocarcinoma patients treated with surgical resection in 2004-2014. Cox regression modeling was used to calculate the concordance index of AJCC 8 in predicting overall survival. N sampling and positivity rates were analyzed over the study period. Results: In our cohort, predicted 5-year overall survival by AJCC 8 was: stage I, 62.5%; II, 50.2%; IIIA, 25.7%; IIIB, 22.1%; IVA, 15.7%; IVB, 6.7% (P < 0.01). The concordance index for the staging system was 0.832. Only 50.7% of the patients had any LN sampling to determine the N stage. LN sampling rates improved from 45.6% in 2004 to 55.1% in 2013 (P < 0.001). However, only 24.5% of patients with any LN sampling had ≥6 LNs resected (12.4% of eligible cohort), with a median LN sample of two. Conclusions: AJCC 8 offers adequate discrimination for GBC staging, especially for node-positive patients. With actual GBC LN sampling rates at 50.7%, and far short of the ≥6 LN threshold, quality improvement measures may need to focus on requiring any LN sampling before raising the minimum to six LNs.