Microwave Ablation Protocol for Liver Metastases to be Studied Across Centers Worldwide | Varian

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Microwave Ablation Protocol for Liver Metastases to be Studied Across Centers Worldwide

Microwave Ablation Protocol for Liver Metastases to be Studied Across Centers Worldwide

Over the past decade or so, evidence continues to accrue that image-guided microwave ablation is a viable approach to treating metastatic colorectal cancer.1,2 Still, while the literature on clinical approaches to the treatment of liver metastases suggests that clinics utilize ablation in some cases, surgical resection remains the standard of care in treatment guidelines and tumor board reviews don’t always include an interventional radiologist.

“Years of retrospective data and case series, and a recent prospective trial suggest that microwave ablation can achieve local tumor control with fewer adverse effects, a quicker return to daily life, and reductions in healthcare costs,”3 explains Kate Pietrovito, senior director of Clinical Operations at Varian. “However, there is much individualized care in the field of interventional radiology. More high-quality evidence is needed to bring it on par with surgery within treatment guidelines.”

To support the additional in-depth research needed to truly evaluate image-guided microwave ablation as a treatment for metastatic colorectal cancer, Varian is pleased to be among the industry partners supporting a clinical trial under the auspices of the Society of Interventional Oncology (SIO), "Ablation with Confirmation of Colorectal Liver Metastases (ACCLAIM) Prospective Trial for Microwave Ablation as a Local Cure."


The ACCLAIM trial, SIO’s first, “proposes to establish microwave ablation (MWA) as the preferred treatment option for selected colorectal liver metastases that can be ablated with sufficient margins,” according to the SIO press release announcing the launch of the study. It is “the first global, prospective trial to use an objective and reproducible technical outcome in its study design, which SIO believes will drive important changes to future treatment guidelines,” the release explains. “The study involves the use of software to assess the ablation zone and margins and determine if achieving complete margins during an ablation equates to procedural success.”

ACCLAIM Protocol and Study4

The origins of the ACCLAIM study begin with Constantinos Sofocleous, MD, PhD, an interventional radiologist and pioneering researcher in this field. After several investigator-initiated studies, campaigns, and collaborations with other leading ablation experts, Dr. Sofocleous achieved a consensus protocol, ‘Ablation with Confirmation of Colorectal Liver Metastases,’ and became principal investigator for the ground-breaking ACCLAIM study—a multinational, multicenter prospective trial looking primarily at local disease progression at 24 months post ablation, in patients treated for colorectal liver metastases with confirmation of microwave ablation margins in accordance with the ACCLAIM protocol.4

In addition to assessing a standardized, reproducible method of treating this specific disease, the study examines the implementation of image-guidance and treatment-planning software to monitor the treatment as well as patient outcomes over time.4

“We’re excited to see the emergence of software for planning, delivering, and evaluating treatment systematically as an important aspect of how the patients are treated in the study,” Pietrovito says. “The hope is that treatment software will continue to evolve and improve over time through artificial intelligence. Varian has played an instrumental role in developing sophisticated software tools for precision radiation oncology; we’re excited at the prospect of creating solutions for interventional oncology.”

The ACCLAIM study is being conducted at 10 cancer centers worldwide and has already started enrollment at three in the US. Enrollment is expected to include about 275 patients over a three-year period, each with up to three colorectal cancer liver metastases. None of the metastases can be larger than 2.5 cms and must be located away from the confluence in the portal hepatis to avoid damage to bile ducts, central vessels, and other key structures.

“ACCLAIM standardizes a minimally acceptable standard of care, and the study is designed to answer the question of whether we can replicate its treatment results uniformly throughout the world,” Dr. Sofocleous says. “The study is device naïve, so physicians can use any FDA- or EMA-cleared, commercially available microwave ablation system and treatment assessment tool. Clinicians must achieve a minimal 5-millimeter margin, ideally more than 10 millimeters, to assess local tumor control, and to validate what we’re seeing in other research—a 90% local progression-free survival at two years from the time of treatment.”

Dr. Sofocleous is optimistic that results from the study could help improve approaches to using interventional image-guided therapies throughout the world.

“In addition to exploring whether we could achieve high levels of local tumor control by mandating treatment zone evaluation with the latest software techniques, the study could help strengthen recommendations for microwave ablation in standard-of-care guidelines, for instance where surgery may be too invasive or the patient is not a good surgical candidate,” he adds.

Colorectal cancer is the third most common cancer worldwide, according to the World Cancer Research Fund International, and in 2020, there were more than 1.9 million new cases of colorectal cancer.5 Of new colorectal cancer diagnoses, approximately 20% of patients have metastatic disease at initial diagnosis and another 25% of those with localized disease will later develop metastases.6

“Varian is committed to advancing minimally invasive cancer treatment options, and we believe that by increasing the quality of evidence with high-quality data that supports interventional procedures, we can help give interventional radiologists a permanent seat on the tumor board review panel,” Pietrovito concludes.

Dr. Sofocleous offers paid advisory expert consultancy to Varian for product development and has received research support from Varian. He was not compensated for his participation in the preparation of this article.


1 Takahashi, H., & Berber, E. (2019). Role of thermal ablation in the management of colorectal liver metastasis. Hepatobiliary Surgery and Nutrition, 9(1), 49-58.
2 Meijerink MR, Puijk RS, van Tilborg A, et al. Radiofrequency and Microwave Ablation Compared to Systemic Chemotherapy and to Partial Hepatectomy in the Treatment of Colorectal Liver Metastases: A Systematic Review and Meta-Analysis. Cardiovasc Intervent Radiol 2018;41:1189-204.
3 Tinguely P, Laurell G et al. Ablation versus resection for resectable colorectal liver metastases - Health care related cost and survival analyses from a quasirandomised study. Eur J Surg Oncol. 49 (2023) 416-425.
4 Ablation With Confirmation of Colorectal Liver Metastases (ACCLAIM). Society of Interventional Oncology. (2023). (Clinicaltrials.gov Identifier NCT0526516).
5 World Cancer Research Fund International. (n.d.) Colorectal cancer statistics. Accessed April 28, 2023.
6 Biller LH, Schrag D. Diagnosis and Treatment of Metastatic Colorectal Cancer: A Review. JAMA. 2021 Feb 16;325(7):669-685.