VARIATION IN BREAST-CANCER SURGERY IN ONTARIO

Objectives: To analyse the extent of variation by county and hospital in the use of breast-conserving surgery in the initial management of b reast cancer and to assess some factors that might explain the observe d variation. Design: Population-based retrospective cohort study. Sett ing: Ontario. Patients: All women with breast cancer newly diagnosed f rom Jan. 1, 1989, to Dec. 31, 1991. Main outcome measure: Proportion o f women undergoing unilateral breast cancer surgery who had breast-con serving surgery in each hospital and county. Results: Of the 14 570 wo men with newly diagnosed breast cancer 12 815 (88.0%) underwent unilat eral breast cancer surgery. The mean proportion of breast-conserving p rocedures by county was 52% and ranged from 11% to 84%. The proportion of breast-conserving procedures in individual hospitals with one or m ore cases of breast cancer per month ranged from 6% to 84%. The variat ions in the rates between hospitals was greater than that expected by chance alone (p < 0.0001). Conclusions: There was marked variation at the hospital and county level in the use of breast-conserving surgery in the initial management of breast cancer. This variation was strongl y associated with the hospital where the surgery was performed.