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

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: <18: 54%, 18-30: 36%; >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 <18 category, 95% of patients received recommendations of hormonal therapy only, in the >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.