This month's paper assessed the potential non-inferiority of thermal ablation compared with surgical resection in patients with small-size resectable colorectal liver metastases.
Thermal ablation versus surgical resection of small-size colorectal liver metastases (COLLISION): an international, randomised, controlled, phase 3 non-inferiority trial
Susan van der Lei, Robbert S Puijk, Madelon Dijkstra, Hannah H Schulz, Danielle J W Vos, Jan J J De Vries, et al
Lancet Oncol 2025; 26: 187–99
What is known about the subject?
Surgical resection is the first-choice treatment option for treating colorectal liver metastases with reported 10-year survival rates of up to 24%. Thermal ablative methods have become increasingly popular as an additional treatment alongside surgical resection, or as a standalone treatment when the surgical removal of metastatic sites is not possible. Thermal ablation has been established as a safe and effective means of eradicating disease that spares the parenchyma in patients who are frail or unfit for surgery.
However, advances in local effectiveness and the ease of repeating ablations in case of local tumour progression following percutaneous ablations have instigated the discussion of whether thermal ablation could serve as an alternative to surgical resection for small-size resectable colorectal liver metastases. In the absence of globally adopted resectability and ablatability criteria, differences in clinical practice have emerged as some centres resect nearly all colorectal liver metastases,
whereas others have gradually shifted towards ablating most small-size metastases.
What does this study add?
In the COLLISION trial 300 patients were randomly assigned to the ablation/experimental group (148 patients) or the surgical resection/control group (148 patients). The trial stopped early for meeting predefined criteria for early benefit: a high likelihood (conditional power >90%) of proving non-inferiority regarding overall survival, a non-inferior local control, and fewer adverse events with thermal ablation compared with surgical resection for small-size colorectal liver metastases (≤3 cm). The decision to halt recruitment was substantiated by increasingly difficult accrual due to evolving medical insights, as continuing was deemed unethical and would likely extend the trial by at least 6 more years. No evidence for a difference in overall survival between the treatment groups was found.
Implications for colorectal practice
Both thermal ablation and surgical resection should be considered equally effective treatment options for patients with colorectal liver metastases. The outcomes of this randomized-controlled trial challenge previous conclusions from meta-analyses favouring surgical resection over thermal ablation in patients with colorectal liver metastases. However, thermal ablation appears to be a less invasive and equally effective compared to surgery for small size and resectable colorectal liver metastases.