Investigating Mortality Disparities Among Insured Patients With Colon Cancer Treated in an Integrated Health care System and Other Private Settings

Lower socioeconomic status (SES) affects health care delivery and is associated with worse outcomes. Integrated healthcare systems (IHS) may help reduce barriers to health care and affect outcomes. Our aim was to compare outcomes of colon cancer cases diagnosed at the largest IHS in California, Kaiser Permanente Southern California (KPSC), to other insured patients (OI) to determine how SES influences mortality.This retrospective cohort study included insured adults in southern California diagnosed with colon cancer between 2009 and 2014, using data from the California Cancer Registry, and followed through 2017. Main outcome was all-cause mortality. Person-year mortality rates were calculated for two groups, KPSC and OI. Multivariable hazard ratios were calculated for association between SES quintiles and mortality.Total of 15 923 patients were diagnosed with colon cancer, 4195 patients (26.3%) within KPSC and 11 728 patients (73.7%) in OI. The overall mortality rate per 1000 person-years (PY) was lower in KPSC [103.8/1000 PY (95% CI:98.5-109.3)] compared to OI [139.3/1000 PY (95% CI:135.2-143.4)]. Compared to the highest SES group, the lowest SES group did not experience higher mortality risk in the KPSC population, after adjusting for race/ethnicity and other factors (HR, 95% CI = 1.13, .93-1.38). However, in OI patients, lowest and lower-middle SES groups had higher mortality risk compared to the highest SES group (HR, 95% CI = 1.26, 1.13-1.40 and 1.28, 1.16-1.41, respectively).Lower SES was associated with higher mortality risk within the OI group; however, within KPSC no such association was observed. Care coordination in IHS settings mitigate SES-related mortality differences.