Variations in the treatment of early-stage breast cancer in Quebec between 1988 and 1994.

BACKGROUND The influence of organizational factors on the process and outcomes of the treatment of breast cancer has been extensively investigated. Although the quality of care is presumed to be better in larger centres, evidence is inconsistent. This study was conducted to determine whether therapies for patients with breast cancer varied according to hospital caseload. METHODS Women newly diagnosed between 1988 and 1994 with early-stage node-negative primary breast cancer were randomly selected from the Quebec tumour registry and the Quebec hospital discharge database. Data were collected from medical charts, and only women having undergone dissection of the axilla were included in the analyses. Logistic regression analysis was used to adjust for case mix and organizational variables. RESULTS The final sample included 1259 patients with node-negative stage I or II primary breast cancer. The proportion of women who underwent breast-conserving surgery increased significantly with hospital caseload (from 78.0% in hospitals admitting fewer than 25 new cases each year to 88.0% in those admitting 100 patients or more; p for trend < 0.001). This trend remained significant even after statistical adjustment for case mix and organizational factors (p for trend = 0.001). Of the 1039 women who underwent breast-conserving surgery 965 (92.9%) received radiotherapy. Use of systemic adjuvant therapy (tamoxifen or chemotherapy, or both) increased with the number of patients treated in a given centre (from 60.1% to 68.5%), but this trend disappeared after adjustment for case mix and other factors. The proportion of patients receiving systemic adjuvant therapy consistent with published consensus guidelines tended to increase with caseload for those treated in hospitals participating in multicentre clinical trials but decrease with caseload for patients in hospitals not involved in clinical research. INTERPRETATION The care of patients in Quebec with early-stage breast cancer is characterized by a high prevalence of both breast-conserving surgery and systemic adjuvant therapy. Large centres, especially those actively involved in clinical research, rapidly adopt innovative therapeutic modalities.