The volume-mortality relation for radical cystectomy in England: retrospective analysis of hospital episode statistics
OBJECTIVES
To investigate the relation between volume and mortality after adjustment for case mix for radical cystectomy in the English healthcare setting using improved statistical methodology, taking into account the institutional and surgeon volume effects and institutional structural and process of care factors.


DESIGN
Retrospective analysis of hospital episode statistics using multilevel modelling.


SETTING
English hospitals carrying out radical cystectomy in the seven financial years 2000/1 to 2006/7.


PARTICIPANTS
Patients with a primary diagnosis of cancer undergoing an inpatient elective cystectomy.


MAIN OUTCOME MEASURE
Mortality within 30 days of cystectomy.


RESULTS
Compared with low volume institutions, medium volume ones had a significantly higher odds of in-hospital and total mortality: odds ratio 1.72 (95% confidence interval 1.00 to 2.98, P=0.05) and 1.82 (1.08 to 3.06, P=0.02). This was only seen in the final model, which included adjustment for structural and processes of care factors. The surgeon volume-mortality relation showed weak evidence of reduced odds of in-hospital mortality (by 35%) for the high volume surgeons, although this did not reach statistical significance at the 5% level.


CONCLUSIONS
The relation between case volume and mortality after radical cystectomy for bladder cancer became evident only after adjustment for structural and process of care factors, including staffing levels of nurses and junior doctors, in addition to case mix. At least for this relatively uncommon procedure, adjusting for these confounders when examining the volume-outcome relation is critical before considering centralisation of care to a few specialist institutions. Outcomes other than mortality, such as functional morbidity and disease recurrence may ultimately influence towards centralising care.