A biologic signature for breast ductal carcinoma in situ to predict radiation therapy (RT) benefit and assess recurrence risk

Purpose: 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 biologic signature developed in this study provides recurrence risk and predicts radiation therapy (RT) benefit for DCIS patients following breast conserving surgery (BCS). Experimental Design: A biologic 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 Group with IBC risk of 15% (23% IBE). In analysis of DS and RT by Group, the Elevated 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 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.

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