Abstract P6-09-03: Impact of 70-gene signature use on adjuvant chemotherapy decisions in early breast cancer patients: Results of the prospective symphony triple A study

PURPOSE: gene-expression profiles, such as the 70-gene signature (70-GS), are increasingly used as adjunct to conventional clinicopathological prognostic factors to guide adjuvant chemotherapy (CT) decisions. The Dutch guideline suggests use of validated gene-expression profiles in estrogen-receptor (ER) positive (+) early stage breast cancer patients without overt lymph node metastases. We aimed to assess the impact of the 70-GS on CT decisions in ER+ early stage breast cancer patients. PATIENTS AND METHODS: In this prospective observational multicenter study physicians were asked for their opinion whether to administer or omit adjuvant CT before deployment and after obtaining the test result of the 70-GS in this guideline delineated group of patients. RESULTS: Between January 1 2013 And December 31 2015 660 patients, treated in 31 hospitals, were enrolled. Based on the clinicopathological postoperative findings physicians would administer CT in 41%, withhold CT in 16% of patients and refrained from formulating an advice in the remaining 43% of patients letting their recommendation depend on the result of the 70-GS. Estimated 5-year survival benefit of CT administration was 0.8%, 0.6% and 0.7% respectively (p 0,585). The 70-GS result hardly varied in relation to the initial advice of the physician: 56% and 59% had a low-risk profile in patients in whom CT was recommended or discommended respectively (r =0.021, Table 1). In 51% of patients in whom a pre-test recommendation was formulated incorporation of the 70-GS test result changed the initial advice. Adherence to the test result was high for the three groups (range 94-97%). Table 1. Concordance between pre-test CT recommendation of the oncologist and the 70-gene signature (GS) test result. 70-GS test resultPre-test CT recommendationno. patientsLow RiskHigh RiskNo CT10763 (59%)44 (41%)CT270152 (56%)118 (44%)Depends on 70-GS result283174 (61%)109 (39%)Note. Agreement between pre-test oncologist CT recommendation and the 70-GS test result: Pearsons r = -0,031 95%CI (-0,11 – 0,045). Table 2. CT recommendation before vs. after obtaining the 70-GS test result and the actual administration of CT. Post-test CT recommendationAdherence to test result*Actual administered CTAdherence to test result*Pre-test CT recommendationno. patientsNo CTCT%No CTCT%No CT10769 (65%)38 (35%)94%73 (68%)34 (32%)91%CT207156 (58%)114 (42%)97%162 (60%)108 (40%)90%Depends on 70-GS result283173 (61%)110 (39%)95%185 (65%)98 (35%)91%*Percentage of patients in whom the post-test recommendation/actual administered CT was in line with the 70-GS test result (i.e. no CT in case of a low-risk profile and CT in case of a high-risk profile. Note. Change in CT recommendation in patients with a CT or no CT pre-test recommendation McNemar's chi-square test p < 0.001 and p < 0.001 for actual administered CT CONCLUSION: guideline-directed use of the 70-GS in Dutch ER+ early breast cancer patients influenced CT treatment decision in the majority of patients. The physician's tentative CT advice was not associated with the 70-GS test-result. Citation Format: Kuijer A, Straver M, Elias S, Smorenburg C, Wesseling J, Linn S, Rutgers E, Siesling S, van Dalen T. Impact of 70-gene signature use on adjuvant chemotherapy decisions in early breast cancer patients: Results of the prospective symphony triple A study [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-09-03.