Background: This study was conducted to investigate whether annual surgical unit caseload affects extent of breast cancer surgery, breast cancer recurrence or breast cancer-specific survival.
Methods: In a population-based cohort study, 12,604 women diagnosed with breast cancer in Finland during the years 1998-2001 were followed up until the end of year 2008. Surgical units were divided into subgroups: >200, 100-200, 50-99 or <50 breast cancer operations per year. Information on patients, treatment, and follow-up was obtained from two national registries. The analyses were adjusted for age and disease stage. The reliability of the registry information was validated by comparison with information from one hospital area. Cox proportional hazard and logistic regression models were employed in the analyses.
Results: Validation of the registry data showed that date of diagnosis, age, stage, extent of surgery, and date and cause of death were reliably recorded in the registers. Information on radiotherapy was obtained by combining different registry data. Data on local and distant recurrences were not reliable enough to allow analyses. Patients in hospitals with smaller caseloads underwent mastectomy more often than those operated in hospitals with higher caseloads (P < 0.001). Higher caseloads were also related to improved survival (P = 0.031).
Conclusions: National registries should include information on both local and distant recurrences in order to provide reliable population-based data for evaluation of treatment results. Centralization of surgery to high-volume centers is supported by a higher incidence of conservative surgery and better survival.