The development of the DCIS score: Scaling and normalization in the Marin General Hospital cohort.

Abstract

190 Background: In selected low-risk patients with DCIS treated with wide local excision without radiation, the DCIS score was validated as a predictor of 10 year risk of an ipsilateral breast event (IBE - recurrence of in situ or invasive carcinoma) (p = 0.02) (Solin; SABCS 2011). As part of the development of the DCIS score, scaling from 0 to 100 and determination of risk group cutoff values was done using 100 patient DCIS samples from Marin General Hospital (MGH) selected to have a wide range of tumor characteristics. Methods: 100 patient specimens diagnosed with DCIS were provided by MGH. The Oncotype DX assay was performed, normalized expression levels for the 16 cancer related genes were determined, the DCIS Score and Recurrence Score (RS) were calculated. Distributions of the DCIS score, RS, and individual gene expression levels were described overall and by tumor characteristics. Treatment and pt outcome data were not available. Results: Samples for 96 pts had sufficient tumor and were evaluable; 47% had high nuclear grade, 52% comedo necrosis, 32% tumor size >10 mm, and 9% were ER-negative by IHC. After scaling and risk group cutoff determination, the DCIS score was low risk (0-38) for 49%, intermediate risk (39-54) for 27%, and high risk (≥55) for 24% of pts (Table). The DCIS score was widely distributed within subgroups defined by each of the clinical and pathology characteristics. Proliferation gene expression levels were low in DCIS, on average, relative to prior studies in invasive breast cancer. 92% had a proliferation gene group score <6.5, the threshold used when the RS is calculated; no threshold is used in calculating the DCIS score. Conclusions: Optimal scaling and risk cutoff determination for a wide range of all clinicopathologic characteristics provides for a wide distribution for the DCIS Score. [Table: see text]