Results of PONDx, a prospective multicenter study of the Oncotype DX® breast cancer assay: Real-life utilization and decision impact in French clinical practice

Abstract Adjuvant chemotherapy shows clear benefits in HER2-positive and triple-negative breast cancer (BC). Its benefits are less universal in BCs expressing hormone receptors. The 21-gene Oncotype DX ® Breast Recurrence Score test was designed for HR+, HER2– early-stage BC before decision on adjuvant chemotherapy. Its validity and utility was demonstrated prospectively across multiple studies. The observational study PONDx characterized the use of Oncotype DX ® Breast in routine practice in France and evaluated its decision impact. Of 882 ER-positive BC patients (67% postmenopausal), most (79%) had N0/Nmic node involvement, grade 2 tumors (68%), tumor size 1–5 cm (88%), and ductal histology (78%). BCs with histopathologically elevated recurrence risk included grade 3: 18%; N1: 21%; Ki67 > 20%: 31%. Recurrence Score results by prognostic category were: 30: 10%. Compared to recommendations before individual availability of the score, results prompted net absolute reductions in chemotherapy recommendations of 36% (total population), and 29% (grade 3 and/or Ki67 > 20% histologies). Decisions reflected prognostic implications: in the Recurrence Score 30 category, 97.5% were recommended additional chemotherapy; 95% followed the final recommendations of their physicians. The Recurrence Score provides independent predictive and prognostic information in ER + N0/N1 early BC, including high-risk subgroups. PONDx further characterizes the population where the test is beneficial in real-life use and fits current clinical needs. Oncotype DX ® Breast enables relevant net reductions in chemotherapy use, sparing patients from serious toxicities. Its therapeutic implications are highly accepted by physicians and patients.