Abstract
Cancer is a major health issue in Thailand. It is characterized by heterogeneous and patientspecific somatic mutations. Current methods for cancer follow-up such as imaging and tumor
marker test (including CEA) lack sufficient sensitivity and specificity for detection of early-stage
cancer and minimal residual disease (MRD). This study aims to use targeted sequencing to
analyze circulating tumor DNA (ctDNA) in plasma as an alternative, non-invasive liquid biopsy
approach for cancer monitoring. Two types of panels were developed and compared for
monitoring breast cancer patients. The first panel, personalized panel, were designed based on
individual somatic mutations identified from each patient’s tumor FFPE samples. The second
panel is a shared panel developed using common somatic mutation data from Thai breast
cancer cohorts and The Cancer Genome Atlas Program (TCGA) database. The shared panel aims
to be a single panel to cover common somatic mutations frequently found in breast cancer
patients. In this study, 16 patients from King Chulalongkorn Memorial Hospital (KCMH) were
enrolled. Each patient’s ctDNA samples were collected before and after surgery, with follow-up
over a period up to 1 year. The results showed that both personalized panel and shared panels
could be used for MRD detection. However, personalized panels exhibited the superior
specificity and lower background noise compared to the shared panel. Additionally, targeted
sequencing data from ctDNA was consistent with imaging results and other clinical data.
Notably, in one patient, ctDNA detection revealed tumor recurrence earlier than radiological
imaging. In summary, the ctDNA analysis by targeted sequencing with customized panel
represents a promising non-invasive alternative approach for detection of MRD, improving
cancer recurrence detection and enabling more accurate treatment planning for breast cancer
patients.
