Abstract P6-06-19: Impact of hospital surgical volume on breast cancer mortality: A population based study in the Netherlands

Abstract

Abstract Background: For some low-volume tumour types hospital surgical volume is associated with better survival. For breast cancer there is still much debate. The aim of this study is to determine to what extent the yearly surgical hospital volume determines the mortality in invasive non-metastatic breast cancer patients. Method: Women diagnosed with primary invasive breast cancer in the period 2001-2005 were selected from the Netherlands Cancer Registry. Hospitals were grouped by their annual volume of surgery for invasive breast cancer. Cox proportional hazard models were performed including all patients with primary non-metastatic breast cancer who underwent breast surgery. Gender, age at diagnosis, morphology, grade, size (pT), number of positive lymph nodes, year of diagnosis and socio economic status (SES) were included as covariates. Follow-up was complete until the 1th of February 2013. Results: In total 58.982 patients with invasive non-metastatic breast cancer were diagnosed during the period 2001-2005. Hospitals were grouped by volume of surgery: less than 75 (n = 19), 76-100 (n = 30), 101-150 (n = 29), 150-199 (n = 9) and 200 or more (n = 14) surgeries per year. Non-metastatic patients had a 8% higher risk of death in a low volume hospitals than a hospital with >200 surgeries per year (HR 1.08, 95%CI 1.02-1.14). Cox regression multivariable analyses: the relation of the number of surgical treated invasive breast cancer per hospital per year and the mortality of patients with non-metastatic breast cancer in the Netherlands, 2001-2005Variable HR95%CINumber of operated invasive breast cancers per yearmore than 200reference 150-1991.030.98-1.09 100-1491.010.97-1.05 75-991.040.99-1.08 less than 751.081.02-1.14Corrected for age, gender, morphology, grade, pT, number of positive lymph nodes, year of diagnosis, socioeconomic status Patient and tumour characteristics like age (HR 1.05, 95%CI 1.05-1.05) and SES (lowest vs highest; HR 1.12, 95%CI 1.07-1.16), grade (low vs high, HR 1.72, 95%CI 1.63-1.82), tumour size (1-2 cm vs 2-5 cm; HR 1.46, 95%CI 1.40-1.51), and a higher number of positive lymph nodes (0 vs 1-3; HR 1.40, 95%CI 1.34-1.46 and 0 vs >10; HR 3.19, 95%CI 3.00-3.39) influenced death to a larger extend than surgical volume. Conclusion: In the Netherlands, surgical hospital volume influences risk of death marginally, and far less than patient and tumour characteristics. No differences in mortality between hospitals with a surgical volume of more than 75 were revealed for invasive non-metastatic breast cancer patients compared to hospitals with more than 200 operations. Over the more recent period of 2007-2012, only 3 hospitals had less than 75 operations on average per year, resulting in an even more comparable mortality between hospitals in future. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-06-19.