Influence of health care systems on mortality in adult patients with cancer.

OBJECTIVES

We compared all-cause mortality in insured patients with cancer who were diagnosed in Kaiser Permanente Southern California (KPSC), the largest integrated health care delivery system in southern California, with that in patients diagnosed in hospitals that serve other private insurance (OPI) plans.

STUDY

DESIGN

Retrospective cohort study.

METHODS

Using the California Cancer Registry, we conducted a cohort analysis of all insured adults diagnosed between 2009 and 2014 with 8 common cancers (breast, prostate, lung, colon, melanoma, endometrium, kidney, and bladder) and followed them through December 2017. The cohort comprised 164,197 patients with cancer. We calculated person-year mortality rates by health care system (KPSC and OPI), and we estimated adjusted HRs for the association between overall mortality and health care system using Cox proportional hazards models accounting for race/ethnicity, demographics, cancer site, tumor characteristics, payer, cancer treatments, and socioeconomic status.

RESULTS

We observed 41,727 deaths during the 9 years of follow-up. We found that the patients diagnosed in KPSC had lower overall mortality rates than in the OPI group, a difference that also held within each age category, racial/ethnic group, and stage at diagnosis. In multivariable models adjusting for relevant covariates, African American/Black patients (adjusted HR, 1.14; 95% CI, 1.06-1.21) and Hispanic patients (adjusted HR, 1.23; 95% CI, 1.16-1.30) in the OPI group had dramatically higher mortality risks than those diagnosed in KPSC.

CONCLUSIONS

Among insured patients with cancer in southern California, those diagnosed within KPSC had lower overall mortality compared with the OPI group. Furthermore, this protective effect was greatest for African American/Black patients and Hispanic patients.