Purpose: Ductal carcinoma in situ (DCIS) patients and their physicians currently face challenging treatment decisions with limited information about the individual's subsequent breast cancer risk or treatment benefit. The DCISionRT biological signature developed in this study provides recurrence risk and predicts radiotherapy (RT) benefit for DCIS patients following breast-conserving surgery (BCS). Experimental Design: A biological signature that calculates an individualized Decision Score (DS) was developed and cross-validated in 526 DCIS patients treated with BCS ± RT. The relationship was assessed between DS and 10-year risk of invasive breast cancer (IBC) or any ipsilateral breast event (IBE), including IBC or DCIS. RT benefit was evaluated by risk group and as a function of DS. Results: The DS was significantly associated with IBC and IBE risk, HR (per 5 units) of 4.2 and 3.1, respectively. For patients treated without RT, DS identified a Low Group with 10-year IBC risk of 4% (7% IBE) and an Elevated Risk Group with IBC risk of 15% (23% IBE). In analysis of DS and RT by group, the Elevated Risk Group received significant RT benefit, HR of 0.3 for IBC and IBE. In a clinicopathologically low-risk subset, DS reclassified 42% of patients into the Elevated Risk Group. In an interaction analysis of DS and RT, patients with elevated DS had significant RT benefit over baseline. Conclusions: The DS was prognostic for risk and predicted RT benefit for DCIS patients. DS identified a clinically meaningful low-risk group and a group with elevated 10-year risks that received substantial RT benefit over baseline.

Prediction of radiotherapy (RT) benefit after breast-conserving surgery (BCS) for DCIS is crucial. The aim was to validate a biosignature, DCISionRT^®, in the SweDCIS randomized trial. Women were randomly assigned to RT or not after BCS, between 1987 and 2000. Tumor blocks were collected, and slides were sent to PreludeDx^TM for testing. In 504 women with complete data and negative margins, DCISionRT divided 52% women into Elevated (DS > 3) and 48% in Low (DS ≤ 3) Risk groups. In the Elevated Risk group, RT significantly decreased relative 10-year ipsilateral total recurrence (TotBE) and 10-year ipsilateral invasive recurrence (InvBE) rates, HR 0.32 and HR 0.24, with absolute decreases of 15.5% and 9.3%. In the Low Risk group, there were no significant risk differences observed with radiotherapy. Using a cutoff of DS > 3.0, the test was not predictive for RT benefit (p = 0.093); however, above DS > 2.8 RT benefit was greater for InvBE (interaction p = 0.038). Recurrences at 10 years without radiotherapy increased significantly per 5 DS units (TotBE HR:1.5 and InvBE HR:1.5). Continuous DS was prognostic for TotBE risk although categorical DS did not reach significance. Absolute 10-year TotBE and InvBE risks appear sufficiently different to indicate that DCISionRT can aid physicians in selecting individualized adjuvant DCIS treatment strategies. Further analyses are planned in combined cohorts to increase statistical power.

Purpose: Ductal carcinoma in situ (DCIS), is a noninvasive breast cancer, representing 20-25% of breast cancer diagnoses in the USA. Current treatment options for DCIS include mastectomy or breast-conserving surgery (BCS) with or without radiation therapy (RT), but optimal risk-adjusted treatment selection remains a challenge. Findings from past and recent clinical trials have failed to identify a ‘low risk’ group of patients who do not benefit significantly from RT after BCS. To address this unmet need, a DCIS biosignature, DCISionRT (PreludeDx, Laguna Hills, CA), was developed and validated in multiple cohorts. DCISionRT is a molecular assay with an algorithm reporting a recurrence risk score for patients diagnosed with DCIS intended to guide DCIS treatment. In this study, we present results from analytical validity, performance assessment, and clinical performance validation and clinical utility for the DCISionRT test comprised of multianalyte assays with algorithmic analysis.Methods: The analytical validation of each molecular assay was performed based on the Clinical and Laboratory Standards Institute (CLSI) guidelines Quality Assurance for Design Control and Implementation of Immunohistochemistry Assays and the College of American Pathologists/American Society of Clinical Oncology (CAP/ASCO) recommendations for analytic validation of immunohistochemical assays.Results: The analytic validation showed that the molecular assays that are part of DCISionRT test have high sensitivity, specificity, and accuracy/reproducibility (≥95%). The analytic precision of the molecular assays under controlled non-standard conditions had a total standard deviation of 6.6 (100-point scale), where the analytic variables (Lot, Machine, Run) each contributed <1% of the total variance. Additionally, the precision in the DCISionRT test result (DS) had a 95%CI ≤0.4 DS units under controlled non-standard conditions (Day, Lot, and Machine) for molecular assays over a wide range of clinicopathologic factor values. Clinical validation showed that the test identified 37% of patients in a low-risk group with a 10-year invasive IBR rate of ~3% and an absolute risk reduction (ARR) from RT of 1% (number needed to treat, NNT=100), while remaining patients with higher DS scores (elevated-risk) had an ARR for RT of 9% (NNT=11) and 96% clinical sensitivity for RT benefit.Conclusion: The analytical performance of the PreludeDx DCISionRT molecular assays was high in representative formalin-fixed, paraffin-embedded breast tumor specimens. The DCISionRT test has been analytically validated and has been clinically validated in multiple peer-reviewed published studies.

Purpose: Breast cancer management is shifting towards personalized treatment regimens, particularly for early-stage, hormone receptor positive (HR+) invasive breast cancer (IBC) patients following breast conserving surgery (BCS) where locoregional recurrence (LRR) rates are low. A critical unmet need is the development of tools that can both improve prognostic risk assessment and identify which patients are likely to benefit or not benefit from adjuvant radiation therapy (RT). Herein we developed and cross validated a novel multi-omic assay to assess LRR risk and expected RT benefit for early-stage HR+/HER2-negative IBCs. Methods: A retrospective multi-institutional cohort of 922 patients (T1-2, N0-1, HR+, HER2-) treated with definitive breast conserving surgery (BCS) with or without adjuvant treatment was used to develop and cross-validate a test to predict IBC LRR after BCS ± RT. Treatment assignment was not randomized. The test integrated NGS and proteomic assay data using two biosignatures to generate results: a Decision Score (DS) to predict 10-year LRR prognosis and a radiation resistance index (RRI) to predict differential RT effect on LRR. Associations between DS and RRI with LRR risk and RT interaction were tested using multivariable Cox models. Results: Increasing continuous DS was associated with increasing LRR risk (HR 3.4 per 5 units; p <.001, n = 922) after adjusting for clinicopathologic risk factors, while RT was associated with reduced LRR risk (HR 0.2; p < .001). Increasing continuous RRI was associated with increasing LRR risk for patients treated with RT (HR = 3.1 per 5 units; RT: RRI p _interaction = 0.002). Biosignature utility was demonstrated for categorical risk groups, which were also associated with differential RT benefit. DS Elevated Risk patients (DS > 5) had higher LRR risk without RT (HR = 4.8; p = .0014) with corresponding 10-year risks of 24% in DS Elevated Risk versus 7% in DS Low Risk (DS ≤ 5). In DS Low Risk patients, a statistically significant reduction in LRR risk (HR = 1.0, p = .96) was not observed. However, in the DS Elevated Risk group, RT was associated with decreased LRR risk (HR = 0.4, p = .0097) for patients with a lower radio resistance index (DS > 5, RRI ≤ 5), whereas RT was not associated with a statistically significant reduction in LRR risk (HR = 0.8, p = .51) for patients with a higher radio resistance index (DS > 5, RRI > 5). Conclusions: In this large retrospective, non- randomized multi-institutional cohort, the novel multi-omic biosignature was associated with lower and higher LRR risk after BCS and associated with statistically significant differential RT effect for LRR risk reduction. Clinically meaningful risk groups that were associated with differential RT benefit were identified using the biosignature, supporting its potential utility in the assessment of the LRR risk in early-stage HR+/HER2-negative IBC. Further clinical validation studies are in process, and prospective validation studies are being planned to establish the role of the test in clinical practice.

1019 Background: Ductal carcinoma in situ (DCIS) is a heterogeneous disease associated with a spectrum of risk for ipsilateral breast events (IBE). Reducing overtreatment is an important unmet need for DCIS patients. Methods: Patients were from Uppsala University Hospital diagnosed 1986 - 2004, and University of Massachusetts diagnosed 1999 -2008, treated with breast conserving surgery (BCS) with (56%) or without (44%) radiation therapy (RT). Biomarkers (p16/INK4A, Ki-67, COX-2, PgR, HER2, FOXA1, SIAH2 via IHC/ISH) were assessed in FFPE tissue by board-certified pathologists. Pathological and clinical data were collected from medical records. A multi-marker based prognostic was developed on the combined patient sets (n = 600, 8.1 year median follow-up) using multiple cross-validation (patients divided into independent training and testing subsets). Patients with DCIS detected by mammography screening (n = 379) were then stratified into risk categories defined by the multi-marker based prognostic or clinicopathologic risk (“not low” defined as Size > 2.5 cm or Grade 3). Ten-year invasive IBE outcomes were assessed using Kaplan-Meier and Cox proportional hazards analyses. Results: Size/Grade did not significantly differentiate invasive risk. However, the multi-marker based prognostic stratified patients treated without RT (p < 0.001). Patients with “low” multi-marker invasive risk treated without RT had only a 5% (+/- 5%) 10-yr invasive IBE rate. Conclusions: The multi-marker prognostic identified patients at different risks for invasive IBEs in cross-validation. Patients in the “low” multi-marker risk category had a low invasive event rate regardless of RT. The value of this DCIS prognostic is being evaluated in multiple independent validation studies.