Comparison of Local Recurrence Risk Estimates After Breast-Conserving Surgery for DCIS: DCIS Nomogram Versus Refined Oncotype DX Breast DCIS Score

Abstract

Background: A ductal carcinoma in situ (DCIS) Nomogram integrating 10 clinicopathologic/treatment factors and a Refined DCIS Score (RDS) that incorporates a genomic assay and three clinicopathologic factors (Oncotype DX DCIS Score) are available to estimate DCIS 10-year local recurrence risk (LRR). This study compared these estimates.

Methods: Patients 50 years of age or older with DCIS size 2.5 cm or smaller and a genomic assay available were identified. An RDS within 1-2% of the range of Nomogram LRR estimates obtained by assuming use and non-use of endocrine therapy (Nomogram ± ET) was defined as concordant. Assuming a 10-year risk threshold of 10% for recommending radiation, Nomogram ± ET and RDS estimates were compared, and threshold concordance was determined.

Results: For 54 (92%) of 59 patients, the RDS and Nomogram ± ET LRR estimates were concordant. For the remaining 5 (8%) of the 59 patients, the RDS LRR estimates were lower than the Nomogram + ET estimates, with an absolute difference of 3-8%, and thus were discordant. For these five patients, the RDS estimates of 10-year LRR were lower than 10% (range 5-8%) and the Nomogram + ET estimates were 10% or higher (range 11-14%). These five patients with both discordant and threshold-discordant estimates all had close margins (≤ 2 mm).

Conclusions: Among 92% of women 50 years of age or older with DCIS size 2.5 cm or smaller, free-of-charge online Nomogram 10-year LRR estimates were concordant with those obtained using the commercially available RDS (> $4600). Among the 8% with discordant risk estimates, the RDS appeared to underestimate the LRR and may lead to inappropriate omission of radiotherapy. Unless other data show a clinically significant advantage of the RDS (Oncotype DX DCIS Score), the study data suggest that for women 50 years of age or older with DCIS size 2.5 cm or smaller, its use is not warranted.

Fig. 1.

Refined Oncotype DX Breast DCIS Score™ (RDS) and Nomogram with/without endocrine therapy risk estimates for each patient. Estimates were deemed concordant if the RDS was within 1-2% of the Nomogram with/without endocrine therapy range (open circles, concordant estimates; black solid squares, discordant estimates). DCIS ductal carcinoma in situ

Fig 2.

Concordance of 10-year local recurrence risk estimates, as estimated by the Refined Oncotype DX Breast DCIS Score™ as compared to the Nomogram with or without endocrine therapy. *A11 5 discordant estimates were in patients with close (> 0 mm, ≤ 2 mm) margins. DCIS, ductal carcinoma in situ

Fig 3.

Among 12 DCIS patients with close margins (≤ 2 mm), the proportion of patients with risk estimates that reached ≥ 10% 10-year local recurrence risk threshold using the Nomogram without endocrine therapy, Nomogram with endocrine therapy, and the Refined Oncotype DX Breast DCIS Score™. DCIS ductal carcinoma in situ