Volume, process of care, and operative mortality for cystectomy for bladder cancer

Objectives High-volume hospitals have lower mortality rates for a wide range of surgical procedures, including cystectomy for bladder cancer. However, the processes of care that mediate this effect are unknown. We sought to identify the processes that underlie the volume-outcome relationship for cystectomy. Methods Within the Surveillance, Epidemiology, and End Results (SEER)-Medicare data set, we used International Classification of Diseases (ICD)-9 procedure codes to identify 4465 patients who underwent cystectomy for bladder cancer between 1992 and 1999. The preoperative and perioperative processes of care were abstracted from the inpatient, outpatient, and physician files using the procedure and diagnosis codes available through 2002. Logistic models were used to assess the relationship between the process and hospital volume, adjusting for differences in patient characteristics. Results Substantial variation was found in the use of specific processes of care across the hospital volume strata. High-volume hospitals had greater rates of preoperative cardiac testing (odds ratio [OR] 1.57, 95% confidence interval [CI] 1.24 to 1.98), intraoperative arterial monitoring (OR 3.73, 95% CI 3.11 to 4.46), and the use of a continent diversion (OR 4.01, 95% CI 3.03 to 5.30), among many others. Patients treated at low-volume hospitals were 48% more likely to die in the postoperative period (4.9% versus 3.5%, adjusted OR 1.48, 95% CI 1.03 to 2.13). Differences in the use of processes of care explained 23% of this volume-mortality effect. Conclusions High-volume and low-volume hospitals differ with regard to many processes of care before, during, and after radical cystectomy. Although these practices have partly explained the volume-outcome relationships for cystectomy, the primary mechanisms underlying this effect remain unclear.