Figure. Hospital Characteristics, 90-Day Mortality, and Surgical Volume .

Attributes in the year prior to affiliation with a top-ranked cancer hospital were compared with those of the year after affiliation (the year of affiliation was excluded; thus, the analysis spanned 3 years). The McNemar test was used for categorical and Wilcoxon signed rank test for continuous variables. Preaffiliation hospital characteristics were compared with nonaffiliate hospital characteristics using the χ² test for categorical and median 2-sample test for continuous variables. Ninety-day mortality and complex cancer surgery case volume was assessed in patients older than 65 years who underwent nonemergent pulmonary lobectomy, colectomy, gastrectomy, pancreaticoduodenectomy (Whipple), or esophagectomy for cancer. Mortality and volume data in the year prior to and the year after affiliation were only available for hospitals that affiliated in 2014 and 2015 (n = 88). CoC indicates Commission on Cancer.

^aDifference between affiliates and nonaffiliates is significant.

^bDifference between before and after group is significant.