Prospective study of magnetic resonance imaging (MRI) and multiparameter gene expression assay in ductal carcinoma in situ (DCIS): A trial of the ECOG-ACRIN Cancer Research Group (E4112).

534Background: Prior retrospective studies have evaluated breast MRI in DCIS, and prospective-retrospective biomarker studies have shown that the DCIS Score is prognostic for recurrence after BCS alone. E4112 is a prospective cohort study designed to assess the combined impact of breast MRI and DCIS Score on surgical and RT management. Methods: Women diagnosed with screen-detected DCIS on core biopsy, if BCS eligible, underwent breast MRI. Those remaining so following MRI and related biopsies, with no invasive disease, underwent BCS. If final surgical margins were ≥2 mm, the DCIS lesion was submitted for DCIS Score assay. Women with low DCIS Score (≤39, LS) were advised that RT could be avoided; RT was recommended to those with high/intermediate (H/I) scores. The primary objective was to estimate the fraction converting to mastectomy (Mx) following MRI. Secondary objectives included estimation of re-operation rates after first BCS, and DCIS Score distribution.A sample size of 333 evaluable women would all...