Influence of hospital and clinician workload on survival from colorectal cancer: cohort study

Objective To determine whether clinician or hospital caseload affects morta lity from colorectal cancer. Design Cohort study of cases ascertained between 1990 and 1994 by a region- wide colorectal cancer register. Outcome measures Mortality within a median follow up period of 54 months af ter diagnosis. Results Of the 3217 new patients registered over the period, 1512 (48%) die d before 31 December 1996. Strong predictors of survival both in a logistic repression (fixed follow up) and in a Cox's proportional hazards model (va riable follow up) were Duke's stage, the degree of tumour differentiation, whether the liver was deemed clear of cancer by the surgeon at operation, a nd the type of intervention (elective or emergency and curative or palliati ve intent). In a multilevel model, surgeon's caseload had no significant ef fect on mortality at 2 years. Hospital workload, however, had a significant impact on survival. The odds ratio for death within 2 years for cases mana ged in a hospital with a caseload of between 33 and 46 cases per year, 47 a nd 54 cases per year, and greater than or equal to 55 cases per year (compa red to one with less than or equal to 23 cases per year) were respectively 1.48 (95% confidence interval 1.03 to 2.13), 1.52 (1.08 to 2.19), and 1.18 (0.83 to 1.68). Conclusions There was no detectable caseload effect for surgeons managing c olorectal cancer, but survival of patients treated in hospitals with caselo ads above 33 cases per year was slightly worse than for those treated in ho spitals With fewer caseloads. Imprecise measurement of clinician specific " events rates" and the lack of routinely collected case mix data present maj or challenges for clinical audit and governance in the years ahead.