Abstract P5-06-05: Discordant classification and outcomes between Prosigna and Oncotype Dx Recurrence Score for ER-positive, HER2-negative, node-negative breast cancer

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Abstract Background: Several multigene assays are available for managing ER-positive, HER2-negative early stage breast cancer but with little direct comparative information within this patient population. Existing evidence suggests that current multigene assays provide broadly equivalent risk information for the population of women with ER-positive, HER2-negative breast cancers. However, for the individual patient tests may provide differing risk categorization (Bartlett et al, JNCI 2016). We have previously demonstrated the prognostic value of different commercially available tests including Prosigna (ROR) and Oncotype Dx (RS) (Dowsett et al, JCO 2013; Sestak et al, JAMA Onc 2018). Here, we investigate risk classification and 10-year DR rates in patients that had discordant risk categorization between ROR and RS. Methods: A total of 663 postmenopausal women with ER-positive, HER2-negative, node-negative early stage breast cancer from the TransATAC study for whom both signatures were available were included in this analysis. The primary endpoint was distant recurrence (DR). Predefined ROR cut-off points for low/intermediate and intermediate/high of 40/60 were used. Comparisons were made using two sets of RS cut-off points 1) TailoRX cut-off points of 10/25 and 2) original cut-off points of 18/31. Kaplan-Meier curves were used to estimate the mean risk of DR after 10 years of follow-up in predefined risk groups. Results: Using original RS cut-off points, 25 patients (3.8%) had a high-low discordance compared to ROR, with a total of 295 (44.5%) discordant cases. Using the TailoRx cut-off points, 40 patients (6.0%) had a high-low discordance compared to ROR, with a total of 396 (59.7%) discordant cases. Applying original RS cut-off points, patients categorized into ROR low but into intermediate or high by RS (86/365 (23.6%)) had a 10-year DR rate of only 6.3% (2.7-14.6) (Table). In contrast, patients categorized into RS low but into intermediate or high by ROR (144/423 (48.6%)) had a 10-year DR rate of 13.4% (8.3-21.2). Using the TailoRx cut-off points, patients categorized into ROR low but into intermediate or high by RS (261/365 (71.5%)) had a 10-year DR rate of 2.9% (1.4-5.9), while patients with an RS low but intermediate or high by ROR (62/166 (37.3%)) had a 10-year DR rate of 18.2% (10.2-31.2) (Table). Conclusion: Discordance in risk categorization at the individual patient-level between commercially available multigene assays for early stage breast cancer is not uncommon. Our results show that node-negative patients that were classified by ROR as low risk, regardless of RS risk stratification, had an excellent 10-year DR risk with endocrine therapy alone. In contrast, patients that were classified as RS low risk by either cut-off points but were classified as intermediate or high risk by ROR had a significantly worse 10-year outcome. Our results indicate that ROR better categorized women with node negative disease into respective risk groups. Risk stratification and 10-year DR risk (%) according to ROR and RS cut-off points.ROR cut-offsLow (N=365)Intermediate/High(N=298)Original RS cut-offsNumber10-year risk (%)Number10-year risk (%)Low (N=423)2791.5%14413.4%Intermediate/High (N=240)866.3%15424.8%TailoRx cut-offsLow (N=166)1042.1%6218.2%Intermediate/High (N=497)2612.9%23619.5% Citation Format: Ivana Sestak, Sean Ferree, Itay Shemesh, Wesley Buckingham, Jack Cuzick, Mitchell Dowsett. Discordant classification and outcomes between Prosigna and Oncotype Dx Recurrence Score for ER-positive, HER2-negative, node-negative breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-06-05.