186P Oncologists’ agreement on adjuvant therapy recommendations and the need of 21-gene recurrence score assay in HR+/HER2- early breast cancer

21-gene Recurrence Score Assay (OncotypeDx®, RSA) testing is strongly recommended to guide adjuvant chemotherapy in HR+/HER2- early breast cancer (eBC). However, it is not available for all patients. At our site, RSA has been offered since 2012, initially according to a set of regionally defined criteria and with a limited number of tests. Following TAILORx reports, criteria broadened and the number of tests expanded. Here, we investigated whether a high agreement between oncologists might overcome the added value of RSA testing in a real-world scenario. Six staff oncologists of the Breast Cancer Section independently completed a survey on a retrospective series of consecutive patients with HR+/HER2- eBC. Patients had been surgically treated at Hospital del Mar between 2016 and 2019. We addressed three questions: 1) The degree of agreement between oncologists (based on patient age, pTNM, histology, grade, ER/PR levels, and Ki67) on whether chemotherapy (CHT) should have been discussed with the patient besides hormone therapy (HT). High agreement (HiA) was considered if ≥ 5 oncologists agreed either for CHT or for HT, and the rest was considered low agreement (LoA); 2) The proportion of RSA testing in HiA compared to LoA cases; and 3) In patients with HiA that had undergone RSA testing, the rate of change in adjuvant therapy recommendation. We included 291 patients, of which 44% had undergone RSA testing. Mean age was 61 (range 35-91), 75% had stage I and 18% N1 disease. HiA was reached in 80% of cases (234/291): 72% for HT and 28% for CHT. RSA was ordered for 35% (82/234) of HiA cases (49% for HT and 51% for CHT) compared with 82% (47/57) of LoA cases (p<0.001). In the HiA subgroup that had undergone RSA testing, 79% (33/42) of cases with HiA for CHT received HT alone, while 13% (5/40) with HiA for HT received CHT, leading to an overall rate of change of 46% in therapy recommendation after RSA. Oncologists highly agreed on adjuvant therapy recommendations in 80% of cases. RSA testing was more frequent in LoA cases. High agreement between oncologists was not sufficient to overcome the need for RSA testing in driving adjuvant treatment in eBC.