A phase III trial, COLLISION, has revealed that thermal ablation is a safe and effective alternative to surgical resection for treating colorectal liver metastases. The study, published in The Lancet Oncology, demonstrated that thermal ablation achieved non-inferior overall survival (OS) compared to surgical resection, while also exhibiting a superior safety profile.
The COLLISION trial randomly assigned 296 patients with colorectal liver metastases to either thermal ablation or surgical resection of all target lesions. The primary endpoint was overall survival. Secondary endpoints included disease-free survival (DFS), time to progression, and safety.
Key Findings on Survival and Safety
After a median follow-up of 28.9 months, the study found no statistically significant difference in overall survival between the two groups (HR, 1.05; 95% CI, 0.69-1.58; P = 0.83). Approximately 30% of patients in the thermal ablation group and 32% in the surgical resection group had died by the data cut-off.
Specifically, the 1-, 2-, and 5-year OS rates were 92.8%, 79.1%, and 54.5%, respectively, across both groups. In the thermal ablation arm, these rates were 92.7%, 78.5%, and 51.2%, respectively, while in the surgical resection arm, they were 92.9%, 79.6%, and 58.0%, respectively.
Notably, the trial was stopped early due to a pre-defined stopping rule related to the superior safety profile observed in the thermal ablation group. Adverse events occurred significantly less frequently in the ablation arm (19%) compared to the resection arm (46%; P < .0001). Both low-grade and high-grade adverse events were also less frequent in the ablation group (P = .004 for both).
Implications for Clinical Practice
According to Susan van der Lei, MD, PhD, of the department of Radiology and Nuclear Medicine at Amsterdam University Medical Center, "The assumption that thermal ablation should only be used for unresectable [CRC] liver metastases needs to be reconsidered and our results advocate a more individualized approach to treatment, taking into account the specific clinical characteristics of each patient as well as the expertise available within the medical team."
The trial enrolled 342 adult patients with 1 to 10 colorectal liver metastases of 3 cm or smaller that were amenable to both ablation and resection. Patients in the ablation arm received either radiofrequency ablation or microwave ablation. Resection was permitted for lesions not amenable to ablation. Patients in the resection arm underwent resection of all target hepatic metastases, with thermal ablation permitted for unresectable lesions.
Patient characteristics were generally well-balanced between the two groups. The median age was 67.9 years in the ablation arm and 65.1 years in the resection arm. The majority of patients were male (68% vs 72%), had an ASA score of 2 (69% vs 82%), and had primary tumors located in the rectum (39% vs 39%) or that were left-sided (39% vs 34%).
