Long-term survival benefit from third-line treatment for advanced colon cancer: a case report.

Background: Colorectal cancer (CRC) is a common malignancy with a relatively high incidence and mortality rate. Treatment options for metastatic CRC (mCRC) in the third-line setting remain limited. This article reports a case of colon cancer with liver metastases that progressed after comprehensive treatment but achieved a prolonged progression-free survival of over 38 months with third-line immunotherapy combined with targeted therapy. This aim is to improve understanding of CRC with liver metastasis and provide a clinical reference for managing similar cases.

Case presentation: A 69-year-old male presented to the People's Hospital of Xiangxi Autonomous Prefecture in April 2021 with a 2-week history of fatigue and abdominal distension. His medical history included type 2 diabetes mellitus and diabetic peripheral neuropathy, managed with long-term insulin therapy. Based on clinical presentation, imaging studies, gastroscopy and colonoscopy, and pathological findings, he was diagnosed with moderately to poorly differentiated adenocarcinoma of the ascending colon with liver metastasis (cT4aN0M1a IVA, proficient mismatch repair [pMMR], clinical risk score [CRS] 2). The patient received 6 cycles of neoadjuvant chemotherapy with oxaliplatin, calcium folinate, and fluorouracil (the first 3 cycles combined with bevacizumab), followed by radical resection of the primary tumor and resection of complex liver metastases. Postoperatively, he underwent five cycles of adjuvant chemotherapy with oxaliplatin, calcium folinate, and fluorouracil (the last four cycles combined with bevacizumab). In November 2021, bilateral lung metastases were detected. The patient then received three cycles of chemotherapy with fluorouracil, calcium folinate, and irinotecan, but the disease continued to progress. From February 2022 to April 2025, third-line treatment with fruquintinib (targeted therapy) combined with sintilimab (immunotherapy) was initiated.

Conclusion: Fruquintinib combined with sintilimab immunotherapy may represent a promising third-line treatment option for patients with pMMR mCRC.