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The comprehensive capture of relevant details of patients is essential to accurately predict outcomes and benchmark hospital performance.¹ Members of the Oncology NSQIP National Cancer Center Collaborative (ONNCC), established in 2011, were concerned that important oncology-related variables were not captured by the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP). The ONNCC began collecting 3 additional case characteristics representing greater operative complexity and risk with the aim to improve patient risk prediction and case-mix adjustment.²

Trained surgical clinical reviewers from 16 ONNCC hospitals abstracted 3 novel variables not routinely collected in ACS NSQIP (鈥淧revious Surgery in the Operative Region,鈥� 鈥淧revious Radiotherapy to the Operative Region,鈥� and 鈥淧revious Chemotherapy鈥�). All variables were stratified by time from surgery (鈮�90 days vs <90 days). For example, consider a patient with a distant history of prostatectomy and adjuvant pelvic radiotherapy now undergoing low anterior resection for rectal cancer. The operative region (the pelvis) will be reentered; thus, the data coded for this patient is 鈥淧revious Surgery: 鈮�90 days,鈥� 鈥淧revious Radiotherapy: 鈮�90 days,鈥� and 鈥淧revious Chemotherapy: None.鈥�

Five outcomes were modeled (death or serious morbidity [DSM], any surgical site infection, organ-space surgical site infection, reoperation, and readmission).³ Unadjusted odds ratios were calculated for each ONNCC variable. Based on standard ACS NSQIP modeling, multivariable analyses were then conducted for each outcome using forward selection.^1,4 If forward selection identified an ONNCC variable among the 45 standard ACS NSQIP variables, modeling was repeated without the ONNCC variable. Changes in the C statistic and Akaike information criterion (AIC) were assessed at each step to quantify the degree to which each variable added explanatory power to the model, paying particular attention to the contribution of the ONNCC variables. This study was deemed exempt by the institutional review board of Northwestern University.

In unadjusted analyses, 鈥淧revious Surgery鈥� was not associated with any of the studied outcomes. 鈥淧revious Chemotherapy鈥� was associated with greater odds of DSM (unadjusted odds ratio [OR], 1.34 [95% CI, 1.21-1.49]), reoperation (unadjusted OR, 1.75 [95% CI, 1.30-2.36]), and readmission (unadjusted OR, 1.40 [95% CI, 1.13-1.71]) but only greater than or equal to 90 days from the current operation. 鈥淧revious Radiotherapy鈥� was associated with greater odds of DSM (unadjusted OR, 1.12 [95% CI, 0.91-1.37] for <90 days and 1.44 [95% CI, 1.23-1.69] for 鈮�90 days), reoperation (unadjusted OR, 1.71 [95% CI, 1.19-2.45] for <90 days and 1.96 [95% CI, 1.42-2.72] for 鈮�90 days), or readmission (unadjusted OR, 1.32 [95% CI, 1.09-1.60] for <90 days and 1.52 [95% CI, 1.28-1.81] for 鈮�90 days) regardless of when the patients had previous radiation therapy (Table).

The 鈥淧revious Surgery鈥� and 鈥淧revious Chemotherapy鈥� variables were not selected for inclusion in any of the models during multivariable analyses. The 鈥淧revious Radiotherapy鈥� variable was selected for inclusion only in the DSM and reoperation models at steps 10 and 7, respectively. Inclusion of the ONNCC variables increased the AIC for DSM by 0.06% (AIC of 7077.69 with; AIC of 7073.31 without), while the AIC for reoperation decreased by 0.11% (AIC of 5939.10 with; AIC of 5945.50 without) (Figure). The C statistic for every model correspondingly increased as the AIC decreased for each step.

To accurately predict outcomes and risk adjust hospital comparisons, it is important to consider and evaluate new clinically relevant variables. We found that complex cancer-related variables were unable to improve ACS NSQIP modeling.¹ Prior studies combining oncologic data from the National Cancer Data Base with ACS NSQIP data did show some ability to improve patient-level risk prediction, but there was no effect on hospital-level comparisons.⁴ Despite some bivariate associations being significant, we found that the new ONNCC variables did not affect patient-level comparisons and would correspondingly have no effect on hospital-level comparisons. Thus, currently abstracted ACS NSQIP variables provide sufficient adjustment for short-term outcomes of surgical patients undergoing complex cancer operations. Although the ONNCC variables represent clinical scenarios with the potential for poor postoperative outcomes, they do not provide additional statistical explanatory power to justify the added effort required to abstract them given the lack of modeling benefit. The desire for clinical specificity when building predictive models must be weighed against statistical parsimony in the face of data collection burden.⁵

Corresponding Author: Jason B. Liu, MD, Division of Research and Optimal Patient Care, American College of Surgeons, 633 N St Clair, 22nd Floor, Chicago, IL 60611 (jliu@facs.org).

Published Online: August 3, 2016. doi:10.1001/jamasurg.2016.2253.

Author Contributions: Dr Liu had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Study concept and design: Liu, Weber, Berian, Ko, Bilimoria.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: Liu, Weber, Ko.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Liu, Berian, Chen, Cohen, Ko.

Obtained funding: Bilimoria.

Administrative, technical, or material support: Berian.

Study supervision: Berian, Cohen, Bilimoria.

Conflict of Interest Disclosures: None reported.

Funding/Support: This work was funded by the Northwestern Institute for Comparative Effectiveness Research in Oncology. Dr Liu鈥檚 position is supported by the American College of Surgeons Clinical Scholars in Residence Program and by a research fellowship from the Department of Surgery, University of Chicago. Dr Berian is the John A. Hartford Foundation James C. Thompson Geriatric Surgery Research Fellow whose position is supported by the John A. Hartford Foundation and by the American College of Surgeons Clinical Scholars in Residence Program.

Role of the Funder/Sponsor: The American College of Surgeons had a role in the collection and management of the data but had no role in the design and conduct of the study; analysis or interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Additional Contributions: We acknowledge and thank the 16 centers participating in this pilot study, the individual surgeons representing their institutions in the ONNCC, and especially the surgical clinical reviewers for data collection.