Real-life data of antiandrogens (AA) use in metastatic androgen receptor positive triple negative breast cancer (AR+ TNBC): The ATOVAT retrospective French cohort.

e13074 Background: AR+ TNBC account for around 25% of all TNBC. Identification of those patients is difficult since AR expression (IHC) testing is not routinely recommended. Published data of 3 trials using different antiandrogens (AA) found clinical benefit rates (CBR) at 6 months ranging from 19 to 29% with excellent toxicity profiles. The aim of this retrospective trial was to assess the clinical benefit of AA in real life. Methods: Patients with metastatic AR+ (IHC staining > 10% assessed by local laboratories) TNBC treated with an antiandrogen in metastatic setting were eligible. Patients should have received at least one dose of the following AA: abiraterone acetate, enzalutamide or bicalutamide. Antiandrogens had to be given after documented progression and must not be carried out as part of a clinical trial. Patients could be chemotherapy naïve for their metastatic disease or have received any number of previous line. 30 oncology centers involved in clinical research in France were screened by questionnaire and data were collected in each patient files. The aim was to describe the 6-months CBR and safety in real-life patients. Assessable patients received at least 4 weeks of AA and present at least one disease assessment. Results: 26 patients from 5 French sites were deemed eligible and 24 patients were assessable. Treatment were conducted between January 2002 and January 2021. Median age at initiation of AA was 70 years (range 50-90). 50 % (N = 13) presented liver and/or lung mets and 27% (N = 7) non progressing and non-symptomatic cerebral mets. Median number of previous line of chemotherapy was 3 (range 0-10). AA used were: abiraterone acetate (62%), enzalutamide (8%) and bicalutamide (30%). Median time from mets diagnosis to AA treatment initiation was 18 months (range 0-168). 6-months CBR were 29% (N = 7) with 5 objective responses (2 CR, 3 PR) and 2 SD. 4-months CBR were 33% (N = 8). PFS and OS were 3.2 months (0.8- 36.1) and 9.5 (1.3-63.8) months, respectively. 2 pts further received second line AA with 1 with SD as a best response. 57% (4/7) of patients presenting 6-months clinical benefit received AA in first line versus 18% (3/17).There were no grade 3 or more side effects reported. Conclusions: Real-life data of antiandrogens use in metastatic AR+ TNBC are in line with data from published clinical trials using the same drugs. There were no new safety signal in this retrospective cohort supporting the use of antiandrogens in AR+ (> 10%) TNBC in the absence of other therapeutic opportunity or available clinical trials.