Simosein registry, the French national real-life prospective evaluation of the impact of Endopredict (R) (EPclin) on treatment decision in ER-positive, HER2-negative breast cancers

Breast cancer remains the first cause of death in women worldwide even if the average 10-year survival rate is 83%. It remains difficult to accurately evaluate the risk of recurrence, and consequently the need of chemotherapy, in estrogen receptor (ER)-positive, HER2-negative early breast cancers, at the individual level, leading to overtreatment for some patients. In that context, multigene prognostic scores are proposed in combination with clinicopathological parameters, to guide adjuvant treatment decisions. In our study, patients diagnosed with ER-positive, Her2-negative breast cancer, analyzed with the 12-gene EndoPredictTM test are prospectively included in the national SiMosein registry. The decision for Endopredict testing is determined by an oncological tumor board in expert breast cancer centers. The test is locally performed (10 national laboratories, evaluated by a national quality control exchange program). Clinicopathological parameters are recorded and the treatment decision before and after the genomic test is requested. The aim of the study is to prospectively evaluate the real-life use of the EndopredictTM test and the impact of the recurrence risk on the adjuvant treatment decision. A total of 3153 patients were included between May 2016 and December 2018. Patients are 75.6% post-menopausal (median age: 57.55y) and are mostly diagnosed as invasive ductal carcinoma not otherwise specified (81.2%) with SBR grade 2 (74.02%) and positive Ki67 staining (\u003e14%, 66.4%). Tumor sizes are pT1ab, pT1c or pT2 in respectively 12.1%, 54.7% and 31.4% of the cases. Lymph node involvement is negative (pN0) in 70.5% of the cases. However, 29.5% of cases are pN1-3 with 5.2% of pN1mi. All cases are ER-positive, HER2-negative early breast cancers and 74.8% are progesterone receptor (PR)-positive (PR\u003e10%) and 76.43% of the cases are of luminal B-like subtype. The population evaluated in this prospective study is in accordance to the intermediate prognostic subpopulation of luminal breast cancers where genomic signatures could contribute to guide the adjuvant treatment decision. The risk of relapse at 10 years, as reflected by the EPclin score, is of 13.16% on average, with 55.18% of high risk (positive threshold 10%). Treatment decisions before and after the test were recorded for 599 patients. The decision remains unmodified after the test in 54.59% of the cases. Conversely, change in adjuvant treatment decision was made from hormone therapy (HT) to adjunction of chemotherapy (HT+CT) in 18.20% of the cases and from (HT+CT) to (HT) leading to chemotherapy withdrawn in 27.21%. Finally, the national SiMosein registry, evaluated the utility of the test. The use of EndopredictTM is mostly restricted to the intermediate prognostic subgroup of the early luminal breast subtype as requested by the French health authority (HAS). The test is routinely used in France and clinicians need mainly the test for treatment decision. The EPclin score leads to 45.41% of modification of treatment with a majority of avoidance of chemotherapy (59.93%). Citation Format: Jacqueline Lehmann-Che, Jennifer Wong, Lucie Tixier, Ludovic Lacroix, Magali Triki-Lacroix, Pierre-Jean Lamy, Agnes Garnier, Veronique Quillien, Florence Godey, Isabelle Soubeyran, Gaetan MacGrogan, Laurent Arnould, Juliette Haudebourg, Anne Tallet, Linda Dainese, Caroline Hugonin, Frederique Penault-Llorca. Simosein registry, the French national real-life prospective evaluation of the impact of Endopredict® (EPclin) on treatment decision in ER-positive, HER2-negative breast cancers [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 P3-08-25.