Abstract PO1-17-02: Real-world outcomes of systemic therapy for advanced triple-negative breast cancer: a tertiary centre experience

Abstract Background Despite recent therapeutic developments for advanced triple-negative breast cancer (aTNBC), outcomes are still suboptimal for a significant proportion of patients. Clinical trials focus on a single line of therapy and do not examine outcomes across the whole treatment pathway involving multiple lines of therapy and may not be representative of outcomes in the real world. We evaluated the efficacy of sequential lines of systemic therapies (SACT) in patients with aTNBC treated at our Institution. Methods We conducted a retrospective analysis of patients with aTNBC who commenced SACT at our Institution between 1/12/2011 and 31/12/2020. Patients’ demographics and tumour characteristics were recorded, along with SACT regime used and treatment outcomes. Median overall survival (mOS) was calculated, as was overall response rate (ORR), median progression survival (mPFS) for each line of therapy. Results In total, 239 patients were eligible for inclusion, with a median age of 55 years at diagnosis of aTNBC (range 26-91). Of these, 65 (27.2%) were ≥65. Two hundred and eleven patients (88.3%) had ECOG performance status (PS) 0 or 1 at first-line SACT initiation. Thirty-two (13.4%) had de-novo aTNBC. Of those with recurrent disease (N=207), 110 (53.1%) received neoadjuvant treatment in the early disease setting. Of these, only 8 (7.3%) achieved pathological complete response. In the recurrent disease cohort, 75 (36.2%) had a disease-free interval (DFI) ≤12 months. There was visceral involvement in 144 (60.2%) patients and 10 (4.2%) had bone only disease. The most common histology was invasive ductal (n=142, 59.4%) at metastatic biopsy and 30 (12.6%) were germline BRCA 1/2 mutation carriers. Number of SACT lines ranged from 1 to 8, with most patients (n=140, 58.6%) receiving 1 to 2 lines of treatment only; with 99 (41.4%) receiving ≥3 lines, 60 (25.1%) ≥4 lines and 36 (15.1%) ≥5 lines. Fluoropyrimidines was most commonly used drug class in 1st and in 2nd lines (40.6% and 32.7%, respectively). Eribulin was the most common choice in 3rd line and 4th lines (37.4% and 30%, respectively). Check-point inhibitor-based therapy was used in 6.3% of patients in 1st line, 2.5% in 2nd line and 3.0% in 3rd line. Overall, 25.5% (n=61) of patients were enrolled onto clinical trials. Clinical trial enrolment was most common in third-line (12.1%, n=12). ORR and mPFS were 42.2% (95% CI 35.7-49) and 3.7 months (95% CI 3.0-5.0) respectively in 1st line, 38.5% (95% CI 30.8-46.6) and 3.5 months (95% CI 2.8-4.0) in 2nd line, 30.2% (95% CI 21.3-40.4) and 2.5 months (95% CI 2.1-3.0) in 3rd line, 23.7% (95% CI 13.6-36.6) and 2.1 months (95% CI 2.0-2.8) in 4th line Patients with a DFI 12 months had a longer mPFS compared to patient with DFI ≤12 months at 5.4 (95% CI 3.7– 6.4) and 2.75 (95% CI 2.2– 3.6) months, respectively (P=0.009). At the censor date 18 patients (7.5%) were still alive and mOS was 11.8 months. Conclusions Our real-world data shows that over half of patients only receive one or two lines of systemic therapy for aTNBC, emphasising the importance of therapy choice in the early line setting for aTNBC. These data are important to inform decision-making, discussions with patients and considerations of clinical trials. Table 1. ORR and PFS to First, second, third and fourth-line systemic treatment. Citation Format: Shuai Zhang, Matilde Coriano, Colm Mac Eochagain, Dorothy Yang, Daniel Yiu, Alistair Ring, Nicolo M.L. Battisti. Real-world outcomes of systemic therapy for advanced triple-negative breast cancer: a tertiary centre experience 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 PO1-17-02.