Comparison of Oncotype DX® Recurrence Score® with other risk assessment tools including the Nottingham Prognostic Index in the identification of patients with low-risk invasive breast cancer

Abstract

Oncotype DX® is a gene expression assay that quantifies the risk of distant recurrence in patients with hormone receptor positive early breast cancer, publicly funded in Ireland since 2011. The aim of this study was to correlate Oncotype DX® risk groupings with traditional histopathological parameters and the results of other risk assessment tools including Recurrence Score-Pathology-Clinical (RSPC), Adjuvant Risk Index (Adj RI), Nottingham Prognostic Index (NPI) and the Adjuvant! Online 10-year score (AO). Patients were retrospectively identified from the histopathology databases of two Irish hospitals and patient and tumour characteristics collated. Associations between categorical variables were evaluated with Pearson's chi-square test. Correlations were calculated using Spearman's correlation coefficient and concordance using Lin's concordance correlation coefficient. Statistical analysis was performed using SPSS software, version 22.0.

In our 300 patient cohort, Oncotype DX® classified 59.7% (n = 179) as low, 30% (n = 90) as intermediate, and 10.3% (n = 31) as high risk. Overall concordance between the RS and RSPC, Adj RI, NPI, and AO was 67.3% (n = 202), 56.3% (n = 169), 59% (n = 177), and 36.3% (n = 109), respectively. All risk assessment tools classified the majority of patients as low risk apart from the AO 10-year score, with RSPC classifying the highest number of patients as low risk. This study demonstrates that there is good correlation between the RS and scores obtained using alternative risk tools. Concordance with NPI is strong, particularly in the low-risk group. NPI, calculated from traditional clinicopathological characteristics, is a reliable alternative to Oncotype DX® in the identification of low-risk patients who may avoid adjuvant chemotherapy.

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