Discordance between oncotype DX recurrence score and RSPC for predicting residual risk of recurrence in ER-positive breast cancer

PURPOSE: Oncotype DX, a gene expression assay widely employed to aid decision making on adjuvant chemotherapy use in patients with primary oestrogen receptor-positive (ER+) breast cancer, produces a recurrence score (RS) related to distant disease recurrence (DR) risk (RS%). In node-negative patients, RS can be integrated with clinicopathological parameters to derive RS-pathology-clinical (RSPC) that improves prognostic accuracy. METHODS: Data were collected on patients having clinically indicated tests with an intermediate clinical risk of distant recurrence, and for whom the decision to prescribe chemotherapy remained unclear. Correlation between RS% and RSPC scores was examined. An agreement table was constructed using risk-categorised data. Association between RS%-derived categorical risk assignments and treatment recommendation was evaluated. RESULTS: Data on 171 tests (168 patients) were available. Median DR risk by RS% was 11% (range 3–34%), by RSPC it was 15% (range 4–63%). Correlation between RS% and RSPC was 0.702 (p < 0.001). RS% classified 57.3% of cases as low-, 32.2% intermediate- and 10.5% high-risk for DR; by RSPC proportions were 33.9, 35.7, and 30.4%, respectively. The number of patients receiving chemotherapy recommendations was: 14/87 (16.1%) categorised as low-risk by RS%, 27/49 (55.1%) as intermediate-risk and 12/13 (92.3%) as high-risk. Of 149 patients recommended for endocrine treatment alone, 28 (18.8%) were categorised by RS% as low-risk but by RSPC as intermediate- or high-risk. CONCLUSIONS: In this group of patients, RSPC assessed fewer patients as low-risk and more as high-risk than did RS%. The discordances between the scores indicate that RSPC estimates of risk should be considered when selecting patients for endocrine therapy alone. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10549-017-4514-z) contains supplementary material, which is available to authorised users.