Effect of hospital volume on processes of care and 5-year survival after breast cancer: a population-based study on 25000 women.

PURPOSE: To compare processes of care and survival for breast cancer by hospital volume in Belgium, based on 11 validated process quality indicators.
METHODS: Three databases were linked at the patient level: the Cancer Registry, the population and the claims databases. All women with a diagnosis of invasive breast cancer between 2004 and 2006 were selected. Hospitals were classified according to their annual volume of treated patients: <50 (very low), 50-99 (low), 100-149 (medium) and ≥ 150 patients (high). Cox and logistic regression models were used to test differences in 5-year survival and in achievement of process indicators across volume categories, adjusting for age, tumor grade and stage.
RESULTS: A total of 25178 women with invasive breast cancer were treated in 111 hospitals. Half of the hospitals (N=57) treated <50 patients per year. Six of eleven process indicators showed higher rates in high-volume hospitals: multidisciplinary team meeting, cytological and/or histological assessment before surgery, use of neoadjuvant chemotherapy, breast-conserving surgery rate, adjuvant radiotherapy after breast-conserving surgery, and follow-up mammography. Higher volume was also associated with improved survival. The 5-year observed survival rates were 74.9%, 78.8%, 79.8% and 83.9% for patients treated in very-low-, low-, medium- and high-volume hospitals respectively. After case-mix adjustment, patients treated in very-low- or low-volume hospitals had a hazard ratio for death of 1.26 (95% CI 1.12, 1.42) and 1.15 (95% CI 1.01, 1.30) respectively compared with high-volume hospitals.
CONCLUSION: Survival benefits reported in high-volume hospitals suggest a better application of recommended processes of care, justifying the centralization of breast cancer care in such hospitals.