Racial and ethnic disparities in gallbladder cancer: A two-decade analysis of incidence and mortality rates in the US.

Background: Gallbladder cancer (GBC) is an aggressive malignancy that is usually diagnosed at a late stage. Prior data showed increasing incidence of GBC in the US. However, little is known about race/ethnic-specific incidence and mortality trends of GBC per stage at diagnosis. Therefore, we aimed to conduct a time-trend analysis of GBC incidence and mortality rates categorized by race/ethnicity and stage-at-diagnosis.

Methods: Age-adjusted GBC incidence and mortality rates were calculated using SEER*Stat software from the United States Cancer Statistics database (covers ~98% of US population between 2001 and 2020) and NCHS (covers ~100% of the US population between 2000 and 2020) databases, respectively. Race/Ethnic groups were Non-Hispanic-White (NHW), Non-Hispanic-Black (NHB), Hispanic, Non-Hispanic-Asian/Pacific-Islander (NHAPI), and Non-Hispanic-American-Indian/Alaska-Native (NHAIAN). Stage-at-diagnoses were all stages, early, regional, and distant stages. Joinpoint regression was used to generate time-trends [annual percentage change (APC) and average APC (AAPC)] with parametric estimations and a two-sided t-test (p-value cut-off 0.05).

Results: 76,873 patients were diagnosed with GBC with decreasing incidence rates in all races/ethnicities except NHB who experienced an increasing trend between 2001 and 2014 (APC = 2.08, p < 0.01) and plateauing afterward (APC = -1.21, p = 0.31); (AAPC = 1.03, p = 0.03). Among early-stage tumors (9927 patients), incidence rates were decreasing only in Hispanic (AAPC = -4.24, p = 0.006) while stable in other races/ethnicities (NHW: AAPC = -2.61, p = 0.39; NHB: AAPC = -1.73, p = 0.36). For regional-stage tumors (29,690 patients), GBC incidence rates were decreasing only in NHW (AAPC = -1.61, p < 0.001) while stable in other races/ethnicities (NHB: AAPC = 0.73, p = 0.34; Hispanic: AAPC = -1.58, p = 0.24; NHAPI: AAPC = -1.22, p = 0.07). For distant-stage tumors (31,735 patients), incidence rates were increasing in NHB (AAPC = 2.72, p < 0.001), decreasing in Hispanic (AAPC = -0.64, p = 0.04), and stable in NHW (AAPC = 0.07, p = 0.84) and NHAPI (AAPC = 0.79, p = 0.13). There were 43,411 deaths attributed to GBC with decreasing mortality rates in all races/ethnicities except NHB who experienced a stable trend (AAPC = 0.25, p = 0.25).

Conclusion: Nationwide data over the last two decades show that NHB patients experienced increasing GBC incidence between 2001 and 2014 followed by stabilization of the rates. This increase was driven by late-stage tumors and occurred in the first decade. NHB also experienced non-improving GBC mortality, compared to other race and ethnic groups who had decreasing mortality. This can be due to lack of timely-access to healthcare leading to delayed diagnosis and worse outcomes. Future studies are warranted to investigate contributions to the revealed racial and ethnic disparities, especially in NHB, to improve early detection.