Mutations in Homologous Recombination Genes and Loss of Heterozygosity Status in Advanced-Stage Breast Carcinoma.

Poly (adenosine diphosphate-ribose) polymerase inhibitors (PARPis) have demonstrated antitumor activity in cancers with a homologous recombination deficiency (HRD) and have recently been approved by the FDA for the treatment of germline BRCA1/2-mutation-associated breast cancer. PARPis have also been found to be efficacious in BRCA wild-type (BRCAwt) lesions with high genomic loss of heterozygosity (LOH-high). The goal of this study was to retrospectively investigate the tumor mutations in homologous recombination (HRR) genes and the LOH score in advanced-stage breast carcinomas (BCs). Sixty-three patients were included in our study, 25% of whom had HRR gene mutations in their tumors, including 6% BRCA1/2 and 19% non-BRCA-containing gene mutations. An HRR gene mutation was associated with a triple-negative phenotype. Twenty-eight percent of the patients had an LOH-high score, which, in turn, was associated with a high histological grade, a triple-negative phenotype, and a high tumor mutational burden (TMB). Among the six patients who received PARPi therapy, one had a tumor with a PALB2 mutation other than BRCA and had a clinical partial response. Twenty-two percent of the LOH-low tumors had BRCAwt-HRR gene mutations, compared with 11% of the LOH-high tumors. Comprehensive genomic profiling revealed a subset of breast cancer patients with a BRCAwt-HRR gene mutation that would be missed by an LOH test. The necessity of next-generation sequencing coupled with HRR gene analysis for PARPi therapy requires further investigation in clinical trials.

A phase I/II study of preoperative letrozole, everolimus, and carotuximab in stage 2 and 3 hormone receptor-positive and Her2-negative breast cancer.

PURPOSE: In nonmetastatic hormone receptor-positive and Her2-negative breast cancer, preoperative endocrine therapies can yield outcomes similar with chemotherapy. We evaluated the tolerability and preliminary antitumor activity of preoperative letrozole, everolimus, and carotuximab, a monoclonal antibody targeting endoglin, in nonmetastatic breast cancer. METHODS: Eligible patients had newly diagnosed, stage 2 or 3, hormone receptor-positive and Her2/neu-negative breast cancer. Patients received escalating doses of everolimus; the dose of letrozole and carotuximab were fixed at 2.5 mg PO daily and 15 mg/kg intravenously every 2 weeks, respectively. The primary objective was to determine the safety and tolerability of the combination. Secondary objectives included pharmacokinetic and pharmacodynamic studies and assessments of antitumor activity. RESULTS: Fifteen patients enrolled. The recommended phase 2 dose of everolimus in combination with letrozole and carotuximab was 10 mg PO daily. The most frequent adverse events were headache (67%), fatigue (47%), facial flushing and swelling (47%), gingival hemorrhage (40%), epistaxis (33%), nausea and vomiting (27%). Headache constituted a dose-limiting toxicity. At least two signs of mucocutaneous telangiectasia developed in 92% of patients. Carotuximab accumulated in the extravascular space and accelerated the biodistribution and clearance of everolimus. All patients had residual disease. Gene expression analyses were consistent with downregulation of genes involved in proliferation and DNA repair. Among 6 patients with luminal B breast cancer, 5 converted to luminal A after one cycle of therapy. CONCLUSION: Letrozole, everolimus, and carotuximab were tolerated in combination at their single-agent doses. Pharmacokinetic studies revealed an interaction between everolimus and carotuximab. TRIAL REGISTRATION: This trial is registered with ClinicalTrials.gov (Identifier: NCT02520063), first posted on August 11, 2015, and is active, not recruiting.