COBRA: Characteristics and Outcomes of patients with BReast cancer in phAse I trials at Gustave Roussy Cancer center

Abstract Background: Breast cancer (BC) is the most frequent cancer and the second leading cause of cancer death for women. Although there is a need of new treatments to improve BC outcome, patients with BC are still under-represented in early phase trials, possibly because of the availability of numerous approved treatments and widely recruiting phase II and III trials. We aim to characterize the molecular profile, outcome and prognostic factors of patients with BC treated in a phase I trial at our institution. Methods: We retrospectively analyzed medical records of every BC patients treated consecutively in a phase I trial in the Early Drug Development Department (DITEP) at Gustave Roussy Cancer Center. Multivariate logistic regression models were used to determine the association between known prognostic factors such as ECOG, LDH or albumin levels, number of previous lines of treatment, metastatic sites and duration of treatment. When available, molecular profile was also reviewed. Results: Between April 1st 2008 and December 31th 2021, 4682 patients were enrolled and treated in a phase I trial in our department. Among them, 272 were treated for BC (5.8%): 271 women and 1 man, in 74 different trials. The median number of BC patients treated per year was 16.5 (min 1; max 33). Median time between consented date and C1D1 was 14 days (min 1; max 63). Median age at C1D1 was 50 years old (min 24; max 82). 5 patients (1.8%) were treated in an adjuvant setting (therapeutic vaccine) while all the others were metastatic. 12 patients (4.5%) had brain metastases and 127 patients (47.6%) had liver metastases. 186 patients (70%) had only 1 or 2 metastatic sites, and 81 (30%) had three or more sites. Triple negative was the most common subtype, representing 132 patients (48.5%), 125 (46%) were ER+ and 15 (5.5%) Her2+. Patients received a median number of 3 prior lines before enrollment (min 0; max 19). Overall, only 78 patients (28%) had a genetic testing: 30.7% had a germline BRCA1/2 mutation. 146 patients (54%) had a molecular profile (liquid biopsy or tissue sample) before their enrollment and among them 32,9% were oriented in a trial according to their specific profile. Regarding the type of treatments received: 21.7% were immunotherapy, 73.6% were targeted therapies (46.7% in monotherapy, 26.9% in different combinations with immunotherapy, chemotherapy, radiotherapy or endocrine treatments), 2.9% were chemotherapy and 1.8% endocrine therapy. The overall response rate was 11.1% (0.4% complete response, 10.7% partial response, 37.5% stable disease, 43.8% progressive disease and 7.6% not evaluable). Main reasons for discontinuation of treatment were: progressive disease (80.5%), toxicity (9.6%) and end of trial (6.6%). Median duration of treatment was 2 months (min 0; max 44), only 28.6% of patients were still treated after 3 months of trial and 10% at 6 months. At data cut off (June 21st 2022) median overall survival was 11 months. All patients had discontinued the trial by the time of the analysis: median number of lines of subsequent treatment was 2 (min 0; max 10) and 31 patients (11%) were enrolled in another phase I trial in our center. In a multivariate analysis, there was no prognostic factor associated with duration of treatment whether it was albumin (p=0.76) or LDH levels (p=0.68), ECOG (p=0.67), number of prior lines of treatment (p=0.79) or number of metastatic site (p=0.05). Conclusion: These results are consistent with prior published data as only few patients with BC are addressed for inclusion in a phase I trial, despite response rates and survival rates similar to other phase I patients. We did not find any specific factor associated with duration of treatment. It is likely that a thorough molecular profile could open more treatment options and access to phase I trials. Citation Format: Lauren Seknazi, Arthur Geraud, Vincent Goldschmidt, Capucine Baldini, Stéphane Champiat, Christophe Massard, Sophie Postel-Vinay, Aurelien Marabelle, Rastilav Bahleda, Antoine Hollebecque, Cristina Smolenschi, Anas Gazzah, Jean-Marie Michot, Patricia Martin-Romano, Aurore Vozy, Perrine Vuagnat, François-Xavier Danlos, Arnaud Bayle, Linda Mahjoubi, Barbara Pistilli, Yohann Loriot, Santiago Ponce-Aix, Kaissa Ouali. COBRA: Characteristics and Outcomes of patients with BReast cancer in phAse I trials at Gustave Roussy Cancer center [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-13-02.