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Sources of Funding: This work was supported by the American Cancer Society (RSG 12-323-01-CPHPS), the National Cancer Institute (R01 CA168691, R01 CA174768, T32 CA180984) and the National Institute on Aging (R01 AG048071).

Introduction

Readmissions after surgery lead to low value care (worse outcomes and increased costs). Accountable care organizations (ACO) are doubly incentivized to reduce readmissions through receipt of shared savings bonuses by meeting benchmarks and avoidance of penalties from readmission reduction policies. Our objective was to determine the effect of Medicare Shared Savings Program (MSSP) ACOs on readmission rates after major surgery with a focus on cystectomy.

Methods

We linked a 20% Medicare sample to Leavitt Partners ACO Data and performed a retrospective cohort study of patients undergoing major surgery (cystectomy, abdominal aortic aneurysm (AAA) repair, colectomy, total knee replacement, total hip replacement, lung resection) from 2010 to 2014. We stratified hospitals by MSSP ACO participation and calculated hospital level adjusted readmission and mortality rates using multivariable logistic regression models accounting for clustering within hospitals and procedures. We then performed a difference-in-differences analysis to determine the impact of ACO participation on readmission after major surgery, procedure specific readmissions and mortality rates. We compared outcomes in the pre-implementation and post-implementation periods.

Results

We identified 388,003 patients of whom 61,938 (16%) underwent surgery in an ACO hospital. Overall, 60% were treated in the pre-implementation period. We noted significant secular trends in the non-ACO group from pre- to post-implementation in overall readmission rate (11.0% relative decrease, p<0.001) and mortality (11.1% relative decrease, p<0.001). ACO participation had a significant effect on readmission rate, accounting for an added 7.4% relative decrease, but no effect on mortality rate (Figure A, C; difference-in-differences estimator p=0.024, p=0.25, respectively). Trends for cystectomy were not significant for readmission (Figure B) or mortality in either group.

Conclusions

The overall readmission and mortality rates after major surgery decreased significantly between 2010 and 2014. ACOs accounted for an additional 7.4% reduction in overall readmission rates. Our findings demonstrate a synergistic effect of ACO participation and national readmission policy on readmissions after major surgery.

Funding

This work was supported by the American Cancer Society (RSG 12-323-01-CPHPS), the National Cancer Institute (R01 CA168691, R01 CA174768, T32 CA180984) and the National Institute on Aging (R01 AG048071).