Abstract P6-10-09: Mutational landscape of breast cancer patients in ROME trial: preliminary results

Abstract BACKGROUND: The Rome Trial is a randomized phase II trial (NCT04591431). The aim is to evaluate efficacy and safety of a tailored treatment (TT) compared to standard of care (SoC) in patients with solid tumors. Here we report the preliminary results of the molecular alterations, microsatellite status (MS) and tumor mutational burden (TMB) in metastatic breast cancer (mBC) cohort. METHODS: MBC patients who received at least 1 and no more than 2 systemic treatments were enrolled. Tissue samples were collected within 6 months from the screening. Centralized Next Generation Sequencing (NGS) was performed on both tissue and liquid biopsy. Molecular alterations were evaluated by the Molecular Tumor Board (MTB) using COSMIC, ClinVar, OncoKB and VarSome datasets. Genes with at least 10% frequency of mutation, MS and TMB are reported. RESULTS: From Oct 2020 to June 2022, 980 pts with solid tumors were enrolled. Complete screening mutational data are available for sixty-two pts from the mBC cohort (63% HR+/HER2-, 35% triple negative, 2% HR-/HER2+). NGS was available both on tissue and liquid biopsy in 48 (77%) pts, 14 had only liquid biopsy available due to tissue test failure. 328 genes resulted altered with a median of 7 alteration per pts (0-31). Some pathways were frequently altered: PIK3CA/AKT/MTOR (60%), TP53 (60%), Cell cycle/cycline (35%), FGF/FGFR (26%), BRCA1/2 (17%). The most frequent altered genes were: TP53 (61%), PIK3CA (50%), ESR1 (27%), CCND1 (27%), FGF19 (24%), FGF3 (24%), FGF4 (22%), MYC (22%), FGFR1 (21%), PTEN (21%), EMSY (16%), RB1 (14%), RAD21 (14%), TET2 (13%), BRCA2 (11%), GATA3 (11%), KRAS (10%). No pts with MSI status were reported. Eight (13%) had a high TMB (>10) and the overall median TMB was 5.5 (0-24). Median TMB was similar in tissue and liquid samples (5 and 5.3 mut/mb, p= 0.8). Actionable mutations were detected in 34 pts (54%). Twenty-eight (45%) pts were assigned to a specific TT after the MTB discussion: ipatasertib (16), pemigatinib (5), ipilimumab plus nivolumab (4), lapatinib plus trastuzumab, TDM1 and everolimus (1). MTB requested a germline test for 6 pts: 4 were confirmed (66%; 2 BRCA, 1 PALB2, 1 BRIP1). CONCLUSIONS: The extensive NGS analysis performed in the ROME trial shown that several pathways are commonly mutated in mBC, with target drug potentially available. About 15% of pts had a high TMB but MSI is confirmed as a rare event in breast cancer. Germline mutations have been identified in patients with no prior indication for germline testing. Citation Format: Andrea Botticelli, Simone Scagnoli, Pierfranco Conte, Chiara Cremolini, Paolo Antonio Ascierto, Federico Cappuzzo, Massimo Aglietta, Federica Mazzuca, Ettore Capoluongo, Giovanni Blandino, Umberto Malapelle, Marianna Nuti, Giulia D’Amati, Bruna Cerbelli, Giancarlo Pruneri, Mauro Biffoni, Giuseppe Giannini, Francesco Cognetti, Giuseppe Curigliano, Paolo Marchetti. Mutational landscape of breast cancer patients in ROME trial: preliminary results [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 P6-10-09.