Background: Tumor genomic prognostic assays estimate 10-year local recurrence risk in ductal carcinoma in situ (DCIS) and can guide treatment decisions. This study aimed to evaluate which DCIS patients treated with breast-conserving surgery (BCS) underwent DCIS score genomic testing and the influence of the results on adjuvant treatment recommendations. Methods: The study identified patients from the National Cancer Database (NCDB) who had DCIS treated with BCS from 2010 to 2016. Results: Of 141,047 patients, 4255 (3%) had a DCIS score assessed, 0.3% in 2010 increasing to 5.8% in 2016 (p < 0.001). The patients most likely to undergo DCIS score assessment had more favorable tumor features in the multivariable analysis. The DCIS score result was documented for 91.4% of the tested patients (n = 3888): 70.5% of the low-risk, 14.9% of the intermediate-risk, and 14.6% of the high-risk patients. The patients with low-risk scores were less likely to have radiation than those with intermediate- or high-risk scores among the patients with either ER + (35.0% vs 71.0% or 81.1%) or ER– disease (48.1% vs 77.0% or 85.5%) (each p ≤ 0.001). The patients who had ER + disease with high- and intermediate-risk scores were most commonly treated with both radiation and hormone therapy (HT) (57.1% and 52.2%), whereas the most common treatment for those with a low-risk DCIS score was HT alone without radiation (37.1%). Comparison of genomic testing with clinicopathologic features showed an independent influence of genomic testing on treatment. Conclusions: Use of the DCIS score increased over time, predominantly for favorable DCIS. Patients with a low-risk score were significantly less likely to receive radiation, supporting an impact of the DCIS score on treatment de-escalation.
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