Colorectal liver metastases: partial hepatectomy or thermal ablation

Interventional oncology (IO) is the youngest offshoot of interventional radiology and the most rapidly growing subspecialty in clinical oncology and health care in general. It has successfully established itself as an essential and independent (fourth) pillar within the firmament of multidisciplinary oncologic care, alongside the three established pillars medical oncology, surgery and radiation oncology. Over the years, multiple locoregional treatment modalities have been added to the toolbox of IO physicians. Especially targeted minimally invasive image-guided tumor ablation, otherwise known as radiofrequency ablation (RFA) or microwave ablation (MWA), has proven to be highly effective against primary as well as metastatic disease throughout the body. Their success is chiefly based on the minimally invasive nature, superior safety and toxicity profile, repeatability and often comparable or superior mid- and long-term oncologic outcomes, compared with conventional systemic therapy and surgical resection. Nowadays, these heat-based ablation techniques are recommended curative-intent treatment options for a variety of cancer types, including colorectal liver metastases (CRLM) and hepatocellular carcinoma (HCC). To date, despite the gradual worldwide adoption of thermal ablation, safe and effective characteristics, and similar survival outcomes after partial hepatectomy, medical oncology related societies generally state that thermal ablation should only be reserved for patients who are not amenable for surgery, due to an impaired general health status and/or high comorbidity score, a history of extensive abdominal surgery, (loco)regional tumor progression after prior liver surgery, and/or deep-seated anatomically unresectable tumors or deep-seated anatomically resectable limited disease otherwise requiring major surgery (parenchyma-sparing). For thermal ablation to be considered a fair alternative treatment option for resectable disease, studies directly comparing surgery to thermal ablation need to be finished first. The search towards further optimization of periprocedural management, mainly for the less invasive percutaneous approach, has led to the setup of several comparative cohort studies with the intent to improve long-term oncological outcomes. The results of the local effectiveness of thermal ablation trend over time, anesthetic management, and added value of real-time image guiding techniques are presented in this thesis. Furthermore, the setup of the COLLISION trial, comparing surgical resection to thermal ablation for curative-intent treatable small-size (≤3 cm) CRLM, is documented with the intent to explore the potential of ablation to replace resection as standard of care. As an overarching theme, the first part of this thesis presented new consensus guidelines with a range of oncological outcome related recommendations and time-to-event endpoint definitions in the field of image-guided tumor ablation. The first chapter of this thesis contains an international consensus document describing standardized definitions in oncological outcome measures and time-to-event endpoints regarding all kinds of local (non-)thermal ablative techniques. De following chapters highlight the overal local control, local tumor progression data, overal survival data, complications etc., as known in the literature, as well as the current status of thermal ablation in international guidelines in relation to systemic treatment and surgical resection. An international consensus based algorithm is added which shows the treatment strategy for local treatable CRLM. The following chapter display short- and long-term oncological outcomes based on data from the AmCORE database. Improvement in time, preference for certain anesthetic management, and the added value of software-based and technical tools during a percutaneous ablation procedure were also investigated in this thesis. The under embargo available interim analysis of the COLLISION trial - partial hepatectomy vs. thermal ablation for small-size (<3cm) CRLM - are also included in this thesis.