Minimal residual disease guides postoperative therapy in a patient with ALK-rearranged adenocarcinoma: a case report.

This case report explores the role of circulating tumor DNA (ctDNA)-based minimal residual disease (MRD) monitoring in predicting tumor recurrence or metastasis after consolidative surgery in a patient with ALK-rearranged non-small cell lung cancer (NSCLC). We present a case of a 43-year-old female patient with stage IVA ALK-rearranged NSCLC who initially responded to six months of Alectinib targeted therapy, underwent consolidative surgery with postoperative pathology confirming complete response in the resected primary tumor and lymph nodes, and continued two years of maintenance therapy. During this period, three consecutive MRD tests showed negative results, leading to discontinuation of postoperative therapy. However, two months after stopping Alectinib, the patient developed new brain metastasis in the occipital lobe, necessitating re-initiation of targeted treatment. This case demonstrates the current limitations of ctDNA-based MRD monitoring in reliably predicting recurrence and determining optimal treatment duration in NSCLC. Although MRD monitoring represents an important advancement in NSCLC management, our findings emphasize the need for additional research to validate its clinical applications, particularly in guiding treatment decisions and predicting disease recurrence. The results suggest that larger prospective studies are required to establish evidence-based protocols for MRD monitoring in NSCLC patients.