The LAVA-CRLM trial (Local Ablation Versus Ablative radiotherapy in ColoRectal Liver Metastases) is a prospective, randomised, phase 2 study designed to compare local control and safety of microwave ablation (MWA) versus stereotactic body radiotherapy (SBRT)in patients with colorectal liver metastases and oligometastatic disease. Primary endpoint is freedom form local lesion progression.

Colorectal cancer patients with 1-3 liver metastases (diameter ≤4.0 cm) found unsuitable for resection are randomized 1:1 to either MWA or SBRT. Chemotherapy is allowed. Curative treatment of extrahepatic disease must be initiated in patients with lung metastases and/or primary tumors. Patients will be analyzed according to the intention-to-treat principle.

Inclusion Criteria:

1. Colorectal cancer patients with oligo metastatic disease in the liver (1 to 3 tumors), and where metastases are found unsuitable for resection because of

   1. non-resectability
   2. small metastasis localized deep in the liver, where a parenchyma sparing intervention is preferred over an extensive resection
   3. previous extensive liver surgery
   4. comorbidity

2. The multidisciplinary team should all agree that both percutaneous or open surgical MW-ablation and SBRT are safe as first treatment choice for the individual patient.

3. Tumor sizes ≤4.0 cm

4. Age > 18 years

5. Signed informed consent

Exclusion Criteria:

1. Previous radiotherapy to the liver
2. Liver volume < 700 ml
3. Another active cancer disease within the past 36 months
4. Not able to understand written or oral protocol information

De-identified individual participant data will be made available upon reasonable request to the corresponding author after publication of all analyses of the primary and secondary trial endpoints

Immediately following publication of all analyses of the primary and secondary trial endpoints and until 5 years after.

Investigators whose proposed use of the data has been approved by an independent review committee identified for this purpose for individual participant data meta-analysis. For this please contact the principal investigator of the trial. Data sharing will be conducted in accordance with Danish law on the processing of personal data, regulations of the Danish Data Protection Authority, and applicable health legislation.

Contact Principal investigator Signe Lenora Risumlund Senior Oncologist Department of Oncology, Blegdamsvej 9, 2100 Copenhagen, Capital Region of Denmark, Denmark Signe.lenora.risumlund@regionh.dk