Zisun Choi

Serial Circulating Tumor DNA Analysis with a Tumor-Naïve Next-Generation Sequencing Panel Detects Minimal Residual Disease and Predicts Outcome in Ovarian Cancer

Abstract Circulating tumor DNA (ctDNA) may aid in personalizing ovarian cancer therapeutic options. Here, we aimed to assess the clinical utility of serial ctDNA testing using tumor-naïve, small-sized next-generation sequencing (NGS) panels. A total of 296 patients, including 201 with ovarian cancer and 95 with benign or borderline disease, were enrolled. Samples were collected at baseline (initial diagnosis or surgery) and every 3 months after that, resulting in a total of 811 blood samples. Patients received adjuvant therapy based on the current standard of care. Cell-free DNA was extracted and sequenced using an NGS panel of 9 genes: TP53, BRCA1, BRCA2, ARID1A, CCNE1, KRAS, MYC, PIK3CA, and PTEN. Pathogenic somatic mutations were identified in 69.2% (139/201) of patients with ovarian cancer at baseline but not in those with benign or borderline disease. Detection of ctDNA at baseline and/or at 6 months follow-up was predictive of progression-free survival (PFS). PFS was significantly poorer in patients with detectable pathogenic mutations at baseline that persisted at follow-up than in patients that converted from having detectable ctDNA at baseline to being undetectable at follow-up; survival did not differ between patients without pathogenic ctDNA mutations in baseline or follow-up samples and those that converted from ctDNA positive to negative. Disease recurrence was also detected earlier with ctDNA than with conventional radiologic assessment or CA125 monitoring. These findings demonstrate that serial ctDNA testing could effectively monitor patients and detect minimal residual disease, facilitating early detection of disease progression and tailoring of adjuvant therapies for ovarian cancer treatment. Significance: In ovarian cancer, serial circulating tumor DNA testing is a highly predictive marker of patient survival, with a significantly improved recurrence detection lead time compared with conventional monitoring tools.

Genomic Profiling in Patients with Endometrial Cancer by Deep Sequencing of Vaginal Swabs and Plasma

Abstract Purpose: Endometrial cancer is a common gynecologic malignancy that lacks effective noninvasive screening tools as traditional approaches rely on invasive biopsies. In this large prospective study, we evaluated a novel approach combining vaginal swab DNA and plasma-based ctDNA for genomic profiling to provide a comprehensive framework for diagnosis, prognosis, and disease monitoring. Experimental Design: Adult patients with diverse stages of endometrial cancer, preneoplastic disease, and benign endometrial conditions were prospectively recruited over 2 years. Paired vaginal swab DNA and plasma-based ctDNA were collected preoperatively, and additional plasma samples were obtained at multiple time points postoperatively. Deep next-generation sequencing targeting 101 genes was performed, achieving an average depth exceeding 40,000×. Results: A total of 191 patients contributed 388 samples. Vaginal swab DNA demonstrated 77.7% sensitivity and 96.6% specificity. PTEN mutations were associated with favorable prognosis (HR: 0.27; 95% confidence interval, 0.092–0.77), and TP53 mutations were associated with poor prognosis (HR: 3.7; 95% confidence interval, 1.4–10). A novel classification system based on the mutational profile of PTEN/TP53 identified distinct prognostic groups. Plasma-based ctDNA was significantly associated with stage, lymphovascular invasion, and prognosis (P < 0.01 for all). Patients with preoperative positive plasma-based ctDNA results exhibited poorer outcomes (P < 0.01), whereas postoperative positive ctDNA results enabled early detection of recurrence. Conclusions: These two noninvasive methods play distinct, complementary roles in the management of endometrial cancer. Vaginal swab DNA and novel PTEN/TP53-based classification have distinct prognostic advantages over existing frameworks. Plasma-based ctDNA provides dynamic insights into recurrence risk and disease progression.

Investigation of PARP Inhibitor Resistance Based on Serially Collected Circulating Tumor DNA in Patients With BRCA -Mutated Ovarian Cancer

Abstract Purpose: Patient-specific molecular alterations leading to PARP inhibitor (PARPi) resistance are relatively unexplored. In this study, we analyzed serially collected circulating tumor DNA (ctDNA) from patients with BRCA1/2 mutations who received PARPis to investigate the resistance mechanisms and their significance in postprogression treatment response and survival. Experimental Design: Patients were prospectively enrolled between January 2018 and December 2021 (NCT05458973). Whole-blood samples were obtained before PARPi administration and serially every 3 months until progression. ctDNA was extracted from the samples and sequenced with a 531-gene panel; gene sets for each resistance mechanism were curated. Results: Fifty-four patients were included in this analysis. Mutation profiles of genes in pre-PARPi samples indicating a high tumor mutational burden and alterations in genes associated with replication fork stabilization and drug efflux were associated with poor progression-free survival on PARPis. BRCA hypomorphism and reversion were found in 1 and 3 patients, respectively. Among 29 patients with matched samples, mutational heterogeneity increased postprogression on PARPis, showing at least one postspecific mutation in 89.7% of the patients. These mutations indicate non-exclusive acquired resistance mechanisms—homologous recombination repair restoration (28%), replication fork stability (34%), upregulated survival pathway (41%), target loss (10%), and drug efflux (3%). We observed poor progression-free survival with subsequent chemotherapy in patients with homologous recombination repair restoration (P = 0.003) and those with the simultaneous involvement of two or more resistance mechanisms (P = 0.040). Conclusions: Analysis of serial ctDNAs highlighted multiple acquired resistance mechanisms, providing valuable insights for improving postprogression treatment and survival.

Circulating Tumor DNA and BRCA Reversion Mutation in Advanced or Recurrent Ovarian Cancer Patients With Germline Mutation.

Increasing number of ovarian cancer patients are receiving PARP inhibitor as maintenance or salvage therapy. Predictive factors to PARP inhibitor other than BRCA mutation or HRD status as well as specific resistance mechanism are unknown. Thus, the objective of this study was to prospectively collect serial blood samples in ovarian cancer patients with germline BRCA mutation who receive PARP inhibitor. We investigated circulating tumor DNA (ctDNA) before patients are started on PARP inhibitor and every 3 months thereafter until progression on PARP inhibitor. Through assessment of the changes in ctDNA mutational landscape, we aimed to investigate resistance mechanism to PARP inhibitor including BRCA reversion mutation.