Circulating Tumor Cells as Biomarkers for Relapse Detection in Rectal Cancer with Liver Metastasis: Insights from a Case Report

A 70-year-old female diagnosed case of rectal carcinoma, T3N2M0 received FOLFOX × 2 cycles followed by CAPOX × 2 cycles. She then underwent chemoradiation using Capecitabine as a radiosensitiser, followed by laproscopic tumor resection. The histopathology report showed Tumour Regression Grade 2 (TRG2) response. Subsequently, patient received 4 #CAPOX but developed grade 2 peripheral neuropathy, leading to modification in her treatment to Capecitabine alone for an additional 2 cycles. A whole-body Positron Emitted Tomography-Computed Tomography (PET-CT) scan at this stage showed no evidence of disease. However liquid biopsy test detected the presence of two Circulating Tumor Cells (CTCs). An MRI of the abdomen and pelvis was conducted revealing multiple live lesions (4 mm-6 mm) in segment IV/VIII of the liver, with no sign of local disease. To manage liver metastasis, the patient received 1 cycle of Folfiri while awaiting Selective Internal Radiotherapy (SIRT), followed by 5 cycles of Folfiri. Three years later, her PET scans are observed to be completely normal. This case highlights the critical role of CTC as a biomarker for detecting Minimal Residual Disease (MRD) or relapse. Without CTC monitoring the liver metastasis-that was successfully treated with SIRT, would have likely been missed under the standard cancer care guidelines. As of today, the patient is completely disease free, underscoring the importance of thorough investigation based on advanced CTC liquid biopsy biomarkers in managing rectal cancer with liver metastasis.