Heating (thermal ablation) of small metastases in the liver in patients with colon cancer results in fewer complications and allows the patient to return home faster, all while providing a similar chance of survival as surgically removing the tumours. These are the headline results of the COLLISION trail, carried out by Amsterdam UMC and the Dutch Colorectal Cancer Group, published today in The Lancet Oncology.

"In centres with sufficient expertise, thermal ablation should be seen as the first treatment option. Alongside the improved results, it is also less burdensome for the patient than surgical removal," says Martijn Meijerink, professor of interventional radiology at Amsterdam UMC Cancer Center Amsterdam. Meijerink also emphasizes that doctors must tailor the choice to the specific situation and wishes of the patient.

Destroying tumours with heat

Thermal ablation is a treatment in which a doctor completely destroys the tumours, by puncturing and subsequently heating them from within. Since 2017, 300 patients have participated in the study. Patients either received thermal ablation or they underwent surgery. Researchers then assessed overall survival, safety, length of hospital stay and the likelihood of the tumours recurring inside or outside of the liver. The most important outcome, overall survival, or the lifespan after treatment, was the same for both groups.

Termination of the study

While the initial plan was to include more patients in the trial, it was stopped due to ethical concerns raised by the significant increase in complications in the group that had their tumours surgically removed.

"It had never been studied before whether patients who received ablation had the same survival outcomes as those who underwent surgery. However, the interim analysis showed that the patients in the ablation group were much less likely to have complications, namely 18.9% after ablation versus 45.9% after resection (excision). Furthermore, treatment-related mortality was lower in the ablation group: no patient died following ablation, whereas 2.1% of patients died after resection´’, adds Susan van der Lei, MD, PhD candidate at Amsterdam UMC.

These interim results lead to the discontinuation of the study. During this interim analysis the so-called conditional probability, or in other words likelihood to eventually show equal or superior survival outcomes following ablation, had already exceeded 90%.

"Given the higher rate of complications in the group receiving surgery, it would not have been ethical to continue,” adds van der Lei.

Photo: physician-researcher Susan van der Lei (l) and interventional radiologist Martijn Meijerink perform an ablation: small metastases in the liver are burned away in a patient with colorectal cancer (Amsterdam UMC)
The results from the COLLISION study will be taken into account when adjusting the
national and international guidelines for the treatment of liver metastases in
patients with colorectal cancer. The findings were published today in the
Lancet Oncology.