Canadian breast cancer guidelines: Have they made a difference?

Background: A principal objective of the Canadian Clinical Practice Guidelines for the Care and Treatment of Breast Cancer was to reduce the variation in the way that breast cancer was being treated. To evaluate whether this goal has been reached, we examined variations among surgeons for 4 measures of surgical care and tested for differences in province-wide rates and in variations among surgeons before and after the guidelines were released. Methods: We studied a population-based cohort of 7022 women living in Manitoba in whom breast cancer was diagnosed from 1995 to 2003 inclusive. Demographic, tumour and treatment information was obtained from the Manitoba Cancer Registry. We examined 4 measures of care: breast-conserving surgery, axillary assessment in invasive disease, axillary node dissection in noninvasive disease and the adequacy of axillary node dissection. Generalized linear models were used to test for significant variations in care among surgeons and to test for differences in province-wide rates and variations in these rates among surgeons before and after introduction of the guidelines. Results: We found clinically significant variations in the province-wide rates of all 4 measures examined. These variations were statistically significant for all measures except axillary node dissection in noninvasive disease. No significant differences in either the province-wide rates or in variations in these rates among surgeons before and after introduction of the guidelines were found for any of the measures. Interpretation: Our results suggest that the Canadian breast cancer guidelines are not meeting their stated objective. New strategies for guideline dissemination and implementation may be required.