Circulating tumor DNA (ctDNA) has emerged as a non-invasive “liquid biopsy” for early breast cancer diagnosis. We evaluated the suitability of ctDNA analysis in the diagnosis of early breast cancer after mammography findings, comparing PIK3CA and TP53 mutations between tumor biopsies and pre-biopsy circulating DNA. Matched plasma and frozen fresh tissue biopsies from patients with Breast Imaging-Reporting and Data System (BIRADS) 4c/5 mammography findings and subsequent diagnosis of primary breast cancer were analyzed using NGS TruSeq Custom Amplicon Low Input Panel (Illumina) and plasma SafeSEQ (Sysmex Inostics). The same plasma and tumor mutations were observed in eight of 29 patients (27.6%) with four in TP53 and five in PIK3CA mutations. Sequencing analysis also revealed four additional ctDNA mutations (three in TP53 and one in PIK3CA) previously not identified in three patients tissue biopsy. One of these patients had mutations in both genes. Age, tumor grade and size, immunohistochemical (IHC) subtype, BIRADS category, and lymph node positivity were significantly associated with the detectability of these blood tumor-derived mutations. In conclusion, ctDNA analysis could be used in early breast cancer diagnosis, providing critical clinical information to improve patient diagnosis.

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Background: HER2+ mBC remains incurable, with a need for new HER2-directed therapies and regimens, including chemotherapy-free options. Zanidatamab (zani) is a novel HER2-targeted bispecific antibody that binds HER2 in a unique trans configuration, driving multiple mechanisms of antitumor activity, including complement-dependent cytotoxicity. A CDK4/6 inhibitor combined with endocrine therapy is an approved treatment for HER2-negative/HR+ mBC and this combination has also demonstrated encouraging antitumor activity when paired with HER2-targeted therapy(ies) in HER2+/HR+ mBC. Here, we report results from ZWI-ZW25-202 (NCT04224272), an ongoing single-arm phase 2 study of zani combined with palbociclib (palbo) and fulvestrant (fulv) in pts with HER2+/HR+ mBC. Methods: Eligibility requirements include: HER2+/HR+ unresectable, locally advanced BC or mBC; ECOG PS of 0 or 1; prior treatment with trastuzumab, pertuzumab and T DM1 (additional prior HER2-targeting agents are permitted); and no prior treatment with CDK4/6 inhibitors. Part 1 of the study evaluated the safety and tolerability of the zani/palbo/fulv combination and determined the recommended doses for use in Part 2, where the antitumor activity of the combination is being evaluated. Endpoints include safety outcomes, progression-free survival at 6 months (PFS6), confirmed objective response rate (cORR) per RECIST v1.1; disease control rate (DCR=complete response [CR] plus partial response [PR] plus stable disease [SD]); duration of response (DOR); PFS; and overall survival. Results: As of 24 Feb 2022, 34 pts (33 HER2+/HR+ per central analysis) with a median age of 52 (range 36-77) have been treated. In the metastatic setting, pts had received a median (range) of 4 (1-10) prior systemic regimens, including 3 (1-8) different prior HER2 targeted therapies, and 1 (0-4) endocrine therapy. Seven pts (20%) had prior T DXd treatment and 7 pts had prior fulv treatment. All pts received zani (20 mg/kg Q2W) and standard doses of palbo and fulv. Eighteen pts (53%) remained on treatment; median duration of zani treatment was 6.9 mo (range 0.5-16.3). A dose-limiting toxicity (DLT) of neutropenia occurred in 1 of 7 DLT-evaluable pts in Part 1. Among all pts (n=34), the most common (>20%) treatment (zani, palbo and/or fulv)-related adverse events (TRAEs) were diarrhea (74%), neutrophil count decreased/neutropenia (62%), stomatitis (41%), asthenia (26%), nausea (24%), and anemia (21%). Grade (Gr) ≥3 TRAEs in 2 or more pts included neutrophil count decreased/neutropenia (50%), anemia (6%), diarrhea (6%), and thrombocytopenia (6%). AEs of special interest were all Gr ≤2 and included 4 pts with cardiac events (LVEF decrease of ≥10% from baseline) and 1 pt with infusion-related reaction. There were no treatment-related serious AEs. Palbo was discontinued for 1 pt due to an AE (AST increase); no pt discontinued zani treatment as a result of AEs. Two deaths occurred: 1 due to disease progression and 1 due to an unrelated AE of pneumonia caused by COVID-19. In 29 pts with measurable disease, the cORR was 34.5% (95% CI: 17.9, 54.3), all responses were cPRs, of which 1 is pending CR confirmation. DOR ranged from 2.3 to 14.9+ mo, with 8 confirmed responses ongoing, and the DCR was 93.1% (95% CI: 77.2, 99.2). Interim median PFS was 11.3 mo (range 0.03-16.7; 95% CI: 5.6, not estimable). PFS6 analysis is planned following the completion of enrollment. Conclusions: Zani in combination with palbo and fulv shows encouraging antitumor activity with durable responses in heavily pretreated pts and a manageable safety profile. This regimen has the potential to be a chemotherapy-free treatment option in pts with HER2+/HR+ mBC. Enrollment in the study is continuing. Citation Format: Santiago Escrivá-de-Romani, Emilio Alba, Álvaro Rodríguez-Lescure, Sara Hurvitz, Juan Miguel Cejalvo, Maria Gión, Cristiano Ferrario, Manuel Ruiz Borrego, Rossanna C. Pezo, Erika Hamilton, Marc Webster, Timothy Pluard, Muralidhar Beeram, Begoña Jiménez Rodríguez, Hannah Linden, Cristina Saura, Adam Omidpanah, Phoebe Harvey, Marie-France Savard. Treatment of HER2-positive (HER2+) hormone-receptor positive (HR+) metastatic breast cancer (mBC) with the novel combination of zanidatamab, palbociclib, and fulvestrant [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 PD18-10.

Background: MEN1611 (MEN) is an oral PI3K inhibitor active on the p110α mutant and wild type, β and γ isoforms, while sparing the δ. B-PRECISE-01 is an open-label, 2-arm, phase 1b study investigating MEN1611 in combination with trastuzumab ± fulvestrant in patients with HER2 positive/PIK3CA mutated metastatic breast cancer (MBC). No dose-limiting toxicities were observed during the dose-escalation step and MEN1611 48 mg BID was selected as the recommended phase 2 dose (RP2D) for cohort expansion (CE). Methods: Eligible patients had HER2+/PIK3CA-mutated MBC and were treated with at least 2 prior lines of anti-HER2-based therapy in the advanced/metastatic setting including trastuzumab. Patients received MEN1611 + trastuzumab (MEN+T); hormone receptor positive (HR+) postmenopausal women received M+ T + fulvestrant (MEN+T+F). Recruitment was closed in December 2021. Pooled safety and efficacy data from the two subpopulations of CE are presented herein. Results: As of June 2022, 62 female patients were treated: 56 of them with MEN1611 48 mg BID (25 MEN+T and 31 MEN+T+F). Median age 55.5 years (range 34-78), 21% premenopausal, ECOG PS 0-1: 95.2%. Median metastatic regimens 4; 71.0% had prior pertuzumab and 91.9% had prior T-DM1. Common treatment-emergent adverse events (TEAEs, ≥20%) were diarrhea 66.1%, nausea 45.2%, hyperglycemia 43.6%, anemia 35.5%, asthenia 29.0%, decreased appetite 27.4%, rash 25.8%, aspartate aminotransferase increased 22.6%, vomiting 22.6%, and pyrexia 22.6%. Common TEAEs with CTCAE grade ≥3 (≥10%) were hyperglycemia (22.6%) and diarrhea (11.3%). Most treatment-related AEs (TRAEs) were reversible and manageable by supportive care. TEAEs leading to permanent treatment discontinuation occurred in 9 patients (14.5%), the only TEAE occurring in more than one patient was lipase increased (3.2%). TEAEs caused temporary treatment interruptions in 32 patients (51.6%), the most common being hyperglycemia (21.0%) and diarrhea (9.7%). TEAEs leading to dose reduction occurred in 14 patients (22.6%), the most common being diarrhea (6.5%), hyperglycemia (3.2%) and stomatitis (3.2%). Serious TRAEs were experienced by 12 patients (19.4%): hyperglycemia 6 patients, diarrhea 3 patients, anemia, general physical health deterioration, generalized edema, lipase increased, ketoacidosis and pneumonitis (1 patient each). In the efficacy-evaluable population at the RP2D (n=41) 14 patients (34.1%) showed partial response (MEN+T 5/15, MEN+T+F 9/26), 1 patient (2.4%) had a complete response (MEN+T 1/15) and 23 patients (56.1%) had stable disease (MEN+T 6/15, MEN+T+F 17/26) as best response. At the RP2D, the median (95% CI) overall survival (OS) was 21.9 (11.9, NE) months and the median (95% CI) progression free survival (PFS) 5.6 (3.7, 7.2) months. In the MEN+T group, the median OS was 11.9 (5.7, NE) months and median PFS 3.9 (2.3, 6.7) months. In the MEN+T+F group the median OS was 21.9 (16.9, NE) months and median PFS 5.7 (3.7, 11.5) months. Five patients continue on treatment. Conclusions: Updated results from B-PRECISE-01 demonstrated that MEN1611 combined with trastuzumab ± fulvestrant continued to show a manageable safety profile with encouraging anti-tumor activity and duration of response in heavily pre-treated patients with HER2+/PIK3CA-mutated advanced or metastatic breast cancer. Citation Format: Martine Piccart, Audrey Hennequin, Manuel Ruiz Borrego, Santiago Escrivá-de-Romani, Anja Williams, Begoña Jiménez Rodríguez, Gianluca Del Conte, Sacha J. Howell, Michela Palleschi, Matteo Simonelli, Francois P. Duhoux, Diego Tosi, Bernard Doger de Speville Uribe, Yolanda Jerez Gilarranz, Pierfrancesco Tassone, Giuseppe Curigliano, Simon Waters, Philippe Aftimos, Hans Wildiers, Simona Scartoni, Bartomeu Piza Vallespir, Ram Charan Shankaraiah, Krzysztof Grzegorzewski, Nassir Habboubi. MEN1611, a PI3K inhibitor, combined with trastuzumab ± fulvestrant for HER2+/PIK3CA mutant advanced or metastatic breast cancer: updated safety and efficacy results from the ongoing phase 1b study (B-PRECISE-01) [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 PD18-05.