Post-cystectomy survival predicted by hospital volume

December 31, 2012

Hospital volume is a key predictor of survival for patients with urothelial bladder cancer undergoing radical cystectomy and has a greater impact than surgeon volume, findings from a retrospective analysis suggest.

Nashville, TN-Hospital volume is a key predictor of survival for patients with urothelial bladder cancer undergoing radical cystectomy and has a greater impact than surgeon volume, findings from a retrospective analysis of Surveillance, Epidemiology, and End Results-Medicare data suggest.

“Associations between surgeon volume and hospital volume with patient outcomes have been well described in various aspects of medical care, and this can be broadly understood from the standpoint that each volume metric is associated with a number of factors impacting quality of care. However, surgeon volume and hospital volume are closely intertwined, and their separate influence on outcomes after radical cystectomy has not been well described,” said first author Todd Morgan, MD, assistant professor of urologic surgery at Vanderbilt University, Nashville, TN.

“Although our analyses suggest a greater role of hospital volume than surgeon volume, we don’t think they indicate that surgeon volume is not important. However, at least as we can measure it in our study, there is less clear variation in outcome with increasing surgeon experience,” added Dr. Morgan, who presented the results at the 2012 AUA annual meeting in Atlanta.

The analyses included data for 7,127 patients ages 66 to 90 years operated on between 1992 and 2006.

Surgeons and hospitals were grouped by volume into tertiles by annual number of cases: 1 to 3, 4 to 12, and >12 cases for low-, medium-, and high-volume surgeons and 1 to 15, 16 to 50, and >50 cases for low-, medium-, and high-volume hospitals.

Multivariate analyses of the effects of surgeon volume and hospital volume on overall survival were conducted, and covariates included patient age, gender, race, Charlson comorbidity index, pathologic stage, grade, total node count, node density, number of positive nodes, diversion, year of surgery, and chemotherapy. To determine whether surgeon and hospital volume individually contributed to mortality, three multivariate models were run.

The first model included surgeon volume but not hospital volume and showed surgeon volume was a significant predictor of survival such that the overall mortality risk was significantly greater for patients treated by medium-volume (+11%) and low-volume (+10%) surgeons compared with those operated on by high-volume surgeons. In a model that included hospital volume but not surgeon volume and used high-volume hospitals as the reference group, there was a trend for higher overall mortality risk for patients having cystectomy at a medium-volume hospital (+8%) and a significantly higher risk for patients at a low-volume hospital (+21%).

Better outcomes in high-volume hospitals

In the third model that included both surgeon and hospital volume, adding surgeon volume as a covariate had little impact on the associations between hospital volume and mortality, whereas the impact of surgeon volume on mortality was substantially attenuated (–28% for medium-volume surgeons and –60% for high-volume surgeons) and no longer statistically significant. These findings were corroborated by another analysis comparing the 3-year adjusted survival probabilities for each surgeon volume stratum within each hospital volume stratum and vice versa. There were no statistically significant associations with increasing surgeon volume within any of the hospital volume groups.

However, comparisons within each surgeon volume tertile across hospital volume tiers clearly showed better outcomes as hospital volume status increased. The 3-year survival probability was consistently 8% better at high-volume versus low-volume hospitals for all surgeon volume groups, and the correlation between hospital volume and survival was statistically significant for both medium-volume and high-volume surgeons.

Commenting on the implications of the findings, Dr. Morgan noted that while regionalization of care is controversial, the study results suggest it may be one way to improve outcomes after cystectomy.

“The explanation for the relationship between hospital volume and patient survival after radical cystectomy is certainly multifactorial. While the exact reasons are difficult to tease out, differences between institutions in terms of structural factors and processes of care are the likely etiologies,” Dr. Morgan said.

“However, an alternative would be to identify the practices of high-volume hospitals that are contributing to their better outcomes and transfer those to lower volume centers. That is a substantial challenge but an important one that we should continue to work toward,” he said.