Abstract PO1-14-02: Real world application of a 21-gene recurrence score in a Swiss single center breast cancer population. A comparative analysis of treatment administration before and after TAILORx

Abstract TAILORx was published in July 2018 and showed benefit of chemotherapy (CHT) in premenopausal, HER2 negative breast cancer (BC) patients with a 21-gene intermediate recurrence score (RS). The aim of this study was to determine treatment patterns before and after publication of TAILORx at our Swiss BC center. This is a retrospective analysis of 326 estrogen receptor positive (ER+)/HER2 negative BC patients, treated at Basel University Hospital and Cantonal Hospital Baselland from 2010-2021. Primary endpoint was to assess change in therapy before (cohort A) and after the publication of TAILORx (cohort B) when adjusted for RS category thresholds as defined by the manufacturer and as modified in the TAILORx study protocol. Secondary endpoint was to determine main therapy decision factors. There were no significant differences in the two populations. A included 165 and B 161 patients with a mean RS of 17.72 and 17.89 (p=0.87) respectively. No differences were noted in terms of demographics or tumor characteristics between the two groups. Mean age in A was 58.8 and in B 57.7 years old. There was a tendency for higher ASA scores in B (p=0.262) and higher BMIs in A (p=0.612). There were no differences in RS distribution between A and B when adjusted to manufacturer’s thresholds (p=0.15 for low RS, 0.833 for intermediate and 0.15 for high RS), and subsequently to TAILORx thresholds for RS categories (p=0.817 for low RS, 0.199 for intermediate and 0.795 for high RS). There was no difference in the 2 populations with regards to number of positive nodes (p=0.366) and pN status (p=0.903). In the intermediate node negative population, there were 67 patients in A and 55 in B. No significant differences were noted in demographics (median age 58.9 years in A and 57.2 years in B, p=0.414, menopausal status, p=0.806, relevant comorbidities in 28 patients in A and 21 in B, p=0.864). A relevant tendency for higher ASA scores in B was maintained in this subgroup, with a median score of 3 in B vs 2 in A, p=0.001). Mean tumor size was 20.73 mm in A and 21.17 mm in B (p=0.857) with a mean Ki67 of 20% in both A and B and more cases of higher Ki67 in B (40%) vs A (22%) but not significant (p=0.624). Mean RS was 17.43 in A and 17.75 in B (p=0.674). In the intermediate nodal negative subgroup, the majority had conservative breast surgery (64% in A and B), with less reconstruction in A vs B (46% vs 52%, p=0.031). Radiotherapy (RT) was administered in 66% of women in A and 69% in B (p=0.307) with a mean dose of 53.41 Gy in A and 50.75 Gy in B (p=0.153). Only 4 patients had CHT in A and one patient in B (p=0.775) with one case of severe CHT associated complications in A. Seven patients refuse CHT. In A 31% of patients and in B 44% had osteo-oncologic treatment (p=0.005). There are 7 cases of relapse in A and 3 in B (p=0.492) with one BC related death in A. Tumor board seems to weight more post TAILORx (82% of decision implementation in B vs 63% in A, p=0.38). In the whole population, RS influences decision in the low category, with 91% alignment of RS recommended treatment in A. In B there seem to be a tendency toward more hormonal therapy (138%) but no reduction in CHT application, while in A more patients were administered CHT than recommended by RS guidelines (181%, p 0.001). Therapy decision is not influenced by demographic nor tumor characteristics in A nor B, and there are no differences in surgery (68.4% in A and 64% in B, p=0.352), endocrine therapy (65.4% in A vs. 52% in p=0.113), RT (78% in A and 76% in B, p=0.223). At a median follow up of 62.9 months in A and 19.5 in B, relapse was higher in A (19) vs B (5) (p 0.001) with 5 deaths in A vs none in B. However due to study design which implies different dates of inclusion in the analysis, as well as limited number of events, this data has no power. Before TAILORx decision was mainly dependent on tumor features. After TAILORx other factors, which are particular to every case weight more. This data shows that therapy decisions are not particularly shifted after TAILORx, confirming the emergence of personalised medicine. Demographics, Tumor Characteristics, Therapy and Outcome, RS Categories Thresholds in two Cohorts before and after Publication of TAILORx. What changed? Citation Format: Elena D Chiru, Cvetka Grasic Kuhar, Christian Kurzeder, Marcus Vetter. Real world application of a 21-gene recurrence score in a Swiss single center breast cancer population. A comparative analysis of treatment administration before and after TAILORx abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-14-02.