Comparative effectiveness of ductal carcinoma in situ management and the roles of margins and surgeons

Abstract

Background: The high incidence of ductal carcinoma in situ (DCIS) and variations in its treatment motivate inquiry into the comparative effectiveness of treatment options. Few such comparative effectiveness studies of DCIS, however, have been performed with detailed information on clinical and treatment attributes.

Methods: We collected detailed clinical, nonclinical, pathological, treatment, and long-term outcomes data from multiple medical records of 994 women who were diagnosed with DCIS from 1985 through 2000 in Monroe County (New York) and the Henry Ford Health System (Detroit, MI). We used ipsilateral disease-free survival models to characterize the role of treatments (surgery and radiation therapy) and margin status (positive, close [<2 mm], or negative [≥2 mm]) and logistic regression models to characterize the determinants of treatments and margin status, including the role of surgeons. All statistical tests were two-sided.

Results: Treatments and margin status were statistically significant and strong predictors of long-term disease-free survival, but results varied substantially by surgeon. This variation by surgeon accounted for 15%-35% of subsequent ipsilateral 5-year recurrence rates and for 13%-30% of 10-year recurrence rates. The overall differences in predicted 5-year disease-free survival rates for mastectomy (0.993), breast-conserving surgery with radiation therapy (0.945), and breast-conserving surgery without radiation therapy (0.824) were statistically significant (P(diff) < .001 for each of the differences). Similarly, each of the differences at 10 years was statistically significant (P < .001).

Conclusions: Our work demonstrates the contributions of treatments and margin status to long-term ipsilateral disease-free survival and the link between surgeons and these key measures of care. Although variation by surgeon could be generated by patients' preferences, the extent of variation and its contribution to long-term health outcomes are troubling. Further work is required to determine why women with positive margins receive no additional treatment and why margin status and receipt of radiation therapy vary by surgeon.

Figure 1

Sample selection and analytic flow diagrams. A) Sample selection flow diagram for Monroe County (MC) and Henry Ford Health System (HFHS) samples. B) Analytic plan diagram. BCS = breast-conserving surgery; RT = radiation therapy.

Figure 2

Unadjusted ipsilateral event rates by treatment and margin status. Comparisons were made using Pearson χ² test of independence (two-sided). BCS = breast-conserving surgery; RT = radiation therapy.

Figure 3

Unadjusted hazard functions for ipsilateral event-free survival, accounting for censoring and admitting quadratic duration dependence. A) Hazard functions by treatments, including breast-conserving surgery (BCS) alone, BCS with radiation therapy, and mastectomy. B) Hazard functions by margin status, including positive, close (<2 mm), and negative (≥2 mm) margins.