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Name of the study

Unresectable colorectal liver metastases: stereotactic body radiotherapy versus microwave ablation – a phase II prospective randomized controlled trial for CRLM 3-5 cm

Researchers and contact information

Principal investigators

Prof. dr. M.R. (Martijn) Meijerink

Dr. C. J. A. Haasbeek E:


Trial coordinator:

Drs. S. Nieuwenhuizen, PhD candidate

Phone: 020 444 3047

Summary study

Rationale: Multiple articles report that thermal ablation is a safe and effective treatment for unresectable colorectal liver metastases (CRLM) ≤3cm. However efficacy of thermal ablation decreases with increasing lesion size. Guidelines generally state that thermal ablation is the preferred option for unresectable CRLM ≤3cm and stereotactic body radiotherapy (SBRT) can be considered when thermal ablation is not possible. It remains uncertain what local treatment method should be recommended for unresectable CRLM of 3-5cm.


Primary objective: The primary objective of this study is to compare efficacy of MWA to the efficacy of SBRT with regards to the primary endpoint (local tumour progression free survival at 1 year [1-year LTPFS]) in patients with unresectable CRLM (3 – 5 cm).

Study design: COLLISION XL is a prospective multi-centre phase-II randomized controlled trial.

Primary endpoint: : Primary endpoint is local tumour progression free survival (LTPFS) at 1 year from randomization.

Secondary endpoints: Secondary endpoints are local tumour progression free survival time, overall survival, disease-free survival (DFS), time to progression (TTP), procedural morbidity/toxicity and mortality, assessment of pain and quality of life (QoL).

Sample size: Group sample sizes of 33 in group 1 and 33 in group 2 achieve 81,059% power to detect a difference between the group proportions of -0,33. The proportion in group 1 (the treatment group) is assumed to be 0,665 under the null hypothesis and 0,3350 under the alternative hypothesis. The proportion in group 2 (the alternative treatment group) is 0,665. The test statistic used is the two-sided Z-test with unpooled variance. The significance level of the test is 0,05. To account for a 3% loss to follow-up (NLTFU=2) we need to randomize 68 patients(NR) in total.


Arm A
Microwave ablation

Arm B
Stereotactic body radiotherapy

Participating centers

Participation formally approved by EC

Amsterdam UMC