A Comparison of Predicted Ipsilateral Tumor Recurrence Risks in Patients With Ductal Carcinoma in Situ of the Breast After Breast-Conserving Surgery by Breast Radiation Oncologists, the Van Nuys Prognostic Index, the Memorial Sloan Kettering Cancer Center DCIS Nomogram, and the 12-Gene DCIS Score Assay

Abstract

Purpose: To compare ipsilateral breast event (IBE) risks in patients with ductal carcinoma in situ of the breast (DCIS) post-lumpectomy, as estimated by breast radiation oncologists, the Van Nuys Prognostic Index, the Memorial Sloan Kettering Cancer Center (MSKCC) DCIS nomogram, and the 12-gene Oncotype DX DCIS score assay. Methods and Materials: Consecutive DCIS cases treated with lumpectomy from November 2011 to August 2014 with available DCIS score results were identified. Three radiation oncologists independently estimated the 10-year IBE risk. The Van Nuys Prognostic Index and MSKCC nomogram 10-year IBE risk estimates were generated. Differences and correlations between the IBE estimates and clinicopathologic factors were evaluated. Results: Ninety-one patients were identified for inclusion. Forty-eight percent would have been ineligible for the E5194 study. The mean risk of IBE from the DCIS score assay was 12.4%, compared with a range of 18.9% to 26.8% from other sources. The mean IBE risk from the DCIS score assay was lower regardless of E5194 eligibility. The MSKCC nomogram and DCIS score assay risk estimates were weakly correlated with each other (P = .23) and were each moderately correlated with the other risk estimates (P = .41-.56). When applying the radiation oncologists’ treatment recommendations based on their proposed risk cutoffs, evaluating risk according to the DCIS score assay led to the highest proportion of patients recommended excision alone. Conclusions: IBE risk estimates for this general community cohort of DCIS cases vary significantly among commonly available clinical predictive tools and individual radiation oncologist estimates. Surgical margins and tumor size continue to factor prominently in radiation oncologist decision algorithms. The differences found between the IBE risk estimate methods suggests that they are not interchangeable and the methods that rely on clinicopathologic features may tend to overestimate risk.