PURPOSE: The 21-gene Recurrence Score assay (Oncotype DX) provides prognostic/predictive information in oestrogen receptor positive (ER+) early breast cancer, but access/reimbursement has been limited in most European countries in the absence of prospective outcome data. Recently, two large prospective studies and a real-life 5-year outcome study have been reported. We performed a pooled analysis of prospective European impact studies to generate robust data on impact of use in different clinical subgroups. METHODS: The analysis included four studies (French, German, Spanish, and British) in ER+ human epidermal growth factor receptor 2-negative breast cancer patients (n = 527). Node-positive patients were excluded. RESULTS: The analysis demonstrated that treatment recommendations changed in 32% of patients post-testing; chemotherapy recommendation rate decreased from 55% to 34%. Change rates in the individual studies ranged from 30% to 37%. The highest change rates were in patients originally recommended chemotherapy and in grade II tumours; there was no subgroup without a treatment recommendation change. Notably, 31% of patients with an intermediate Recurrence Score result had a treatment recommendation change suggesting that testing provides actionable information in this group. With the exception of the German study (where chemotherapy rates remained high [41%] post-testing), between-study variability in treatment recommendations decreased post-testing (chemotherapy: from 36-52% to 26-29%; hormonal therapy: from 48-64% to 71-74%). Physicians' confidence regarding treatment recommendations improved in all the studies after testing. CONCLUSION: Recurrence Score testing led to changes in adjuvant chemotherapy use in approximately a third of patients, to an overall reduced chemotherapy use, and to more homogeneous decision making.

J.A. acknowledges FIS PI12/00680 RD12/0036/0051, 2014SGR740 intensification grant ISCIII, and A Ll./nPI12/01421 and RD12/0036/0070.