Prognostic predictability of the new American Joint Committee on Cancer 8th staging system for distal bile duct cancer: limited usefulness compared with the 7th staging system

BackgroundThe new 8th American Joint Committee on Cancer (AJCC) staging has recently been released and there are major changes in distal bile duct (DBD) cancer staging. However, clinical validation is needed before the changes can be widely implemented. MethodsThis study was performed to evaluate the prognostic predictability of the 8th AJCC staging compared with that of the 7th using C statistics. ResultsA total of 293 consecutive patients who had curative-intended surgery were enrolled. There was no significant difference of the 5-year survival rate between 7th T1 and T2 (P = 0.123), but significant difference between T2 and T3 (P = 0.039). There were significant differences in pairwise comparisons between the 8th T stage (T1 vs. T2, P = 0.001; T2 vs. T3, P = 0.014). The number of regional lymph node metastases also showed prognostic predictability. The 8th T and N stage both showed comparable prognostic predictability with the 7th (95% confidential intervals for C; T, -0.043 -0.097, N, -0.001 - 0.008). ConclusionsThe 8th AJCC staging for DBD cancer does not have better prognostic predictability than the 7th stage does. The previous pathologic results would become useless unless they were reviewed entirely. Therefore, introduction of the AJCC 8th staging has to be reconsidered, especially for new T staging.