Blood-Based Minimal Residual Disease in Advanced Epithelial Ovarian Cancer After 1st Line Therapy

Despite high initial response rates to standard first-line therapies (surgery and platinum-based chemotherapy), the majority of patients with advanced high-grade epithelial ovarian cancer experience recurrence within three years. Traditional surveillance methods, including the CA-125 tumor marker and radiological imaging, often lack the sensitivity required to detect minimal residual disease (MRD) at a molecular level, limiting the window for early therapeutic intervention. Circulating tumor DNA (ctDNA) analysis has emerged as a promising, non-invasive technology capable of reflecting tumor-specific genetic mutations and real-time molecular profiling.

This prospective, non-interventional cohort study aims to comprehensively evaluate the clinical utility of blood-based ctDNA as an independent biomarker for predicting recurrence in patients with FIGO stage III-IV epithelial ovarian cancer. The primary objective is to determine whether the presence of ctDNA (MRD positivity) measured immediately after the completion of standard first-line therapy correlates significantly with Relapse-Free Survival (RFS).

To establish a baseline mutational profile, tumor tissue obtained during initial biopsy or debulking surgery (primary or interval) will undergo Next-Generation Sequencing (NGS). Longitudinally, peripheral blood samples (20 mL) will be collected at predefined critical time points: at initial diagnosis (prior to treatment), post-surgery, within 2-4 weeks after the completion of first-line adjuvant or maintenance therapy (baseline for post-treatment MRD), and every 3 months during the follow-up period for up to 36 months or until disease recurrence.

Cell-free DNA (cfDNA) will be extracted from the collected plasma and analyzed using a highly sensitive, validated NGS-based multigene panel (AlphaLiquid® 100). The analysis will quantify major genetic variants (Variant Allele Frequency \[VAF\] ≥ 0.1%).

By tracking changes in ctDNA dynamics and comparing them with standard follow-up modalities, the study will investigate the lead time of ctDNA detection over radiological recurrence and compare its sensitivity and specificity against CA-125. Ultimately, this research seeks to provide robust scientific evidence to support the integration of ctDNA-based MRD monitoring into standard surveillance protocols, potentially enabling personalized tracking strategies and earlier clinical decision-making for high-risk ovarian cancer patients.

• Blood-based ctDNA minimal residual disease (MRD) test (Diagnostic test): A non-invasive diagnostic blood test designed to monitor minimal residual disease (MRD). The procedure involves extracting cell-free DNA (cfDNA) from peripheral blood plasma and performing Next-Generation Sequencing (NGS) using a validated multigene assay (AlphaLiquid 100). This test detects and quantifies tumor-specific genetic mutations (Variant Allele Frequency \[VAF\] ≥ 0.1%) to evaluate molecular-level recurrence after the completion of standard first-line therapy.

Primary outcomes

• Relapse-Free Survival (RFS) according to ctDNA Minimal Residual Disease (MRD) status [Up to 36 months (From the completion of first-line therapy until documented recurrence or the end of the study follow-up period)]: Relapse-Free Survival (RFS) is defined as the time from the completion of standard first-line therapy to the date of the first documented radiological or clinical disease recurrence, or death from any cause. This measure evaluates the correlation between ctDNA positivity (baseline MRD status, measured within 2-4 weeks after completing 1st-line therapy) and RFS. The median RFS and Hazard Ratio (HR) will be compared between the ctDNA-positive and ctDNA-negative patient groups.

Sex: Female, ages: 19 Years to any

Inclusion Criteria:

Women aged 19 years or older. Pathologically confirmed high-grade serous, endometrioid, clear cell, or mixed type ovarian cancer.

FIGO stage III or IV. Patients who have completed primary debulking surgery (PDS) or interval debulking surgery (IDS) and platinum-based chemotherapy (subsequent maintenance therapy, such as bevacizumab or PARP inhibitors, is allowed).

Patients showing radiological or clinical Complete Response (CR) after the completion of platinum-based chemotherapy.

Written informed consent for the study.

Exclusion Criteria:

Radiological progressive disease during or immediately after treatment. Expected survival of 3 months or less. Immunodeficiency or pathological bleeding tendencies. Unable to undergo blood tests or unwilling to undergo repeated blood sampling. Concurrent other solid tumors or history of malignant tumors within the last 5 years.

Refusal to consent to participate in this study.