A recent SEER study identified significant variations in the care of women with DCIS, yet several potential confounding variables were not included. We report a patterns of care study of women with DCIS to better understand the gap between evidence-based knowledge and the management of DCIS.Methods
We studied all cases of DCIS diagnosed through the Ontario Breast Screening Program from 1991 to 2000. Data was obtained by database linkage and chart abstraction. A logistic regression model using generalized estimating equations to adjust for clustering was used.Results
About 320,236 women were screened and 727 individuals were diagnosed with DCIS. The rate of mastectomy was 30% and was associated with multifocality (OR: 3.5 [1.7, 7.1], P = 0.0005), tumor size (OR: >2 cm vs. ≤1 cm: 2.7 [1.3, 5.9], P = 0.01), high nuclear grade (OR: 2.4 [1.1, 5.2], P = 0.03) and surgeon's practice pattern. The rate of axillary dissection (AND) decreased from 36% in 1991–1993 to 20% in 1998–2000. AND was associated with mastectomy, year of surgery and hospital volume (OR: 2.7 [1.3, 5.6], P = 0.01). The use of radiation (XRT) following breast-conserving surgery increased from 39% in 1991 to 51% in 2000. XRT was associated with age<70 years, high nuclear grade (OR: 2.7 [1.2, 6.3], P = 0.02) and tumor size > 1 cm (OR: 2.4 [1.3, 4.4], P = 0.006). Half of cases with margins <1 cm did not receive XRT.Conclusions
Our study corroborates previous reports on the persistent rates of mastectomy and axillary nodal dissection and the limited use of XRT in the treatment of DCIS.