Circulating tumor DNA analysis detects micrometastatic disease and predicts recurrence in a patient with colon cancer: A case report

Colorectal cancer (CRC) is one of the most prevalent and deadly cancers worldwide, and approximately 50% of patients with early-stage disease develop metastases. A critical limitation for successful management of CRC is early disease detection and identification of progression. Next-generation sequencing-based circulating tumor DNA (ctDNA) profiling has emerged as a promising biomarker for the assessment of minimal or molecular residual disease in CRC. PATIENT CONCERNS: The patient was initially diagnosed with resectable CRC with uncertain small lung nodules. DIAGNOSES: The patient was diagnosed with sigmoid colon adenocarcinoma placed at 15 to 20 cm above the anal verge (ypT4N1R0). Lung nodules were found in the apical part of the upper lobe of the right lung and the dorsal segment of the lower lobe of the left lung. INTERVENTIONS: The patient received systemic therapy and local treatment and plasma ctDNA-MRD detection was performed for monitoring the molecular disease status after surgery. OUTCOMES: The patient achieved a complete response after treatment. However, he presented with disease recurrence in liver lesions. The postoperative ctDNA detection suggested the possibility of micrometastatic pulmonary disease, and that was confirmed by follow-up examination. Serial ctDNA detection revealed disease relapse ahead of radiologic imaging by a lead time of 9 months. This case demonstrated the potential of ctDNA analysis to be a sensitive and specific tool for the detection of micrometastatic disease and prediction of recurrence.