Non-interventional observational study of helical tomotherapy for oligometastatic colorectal cancer.

Background and objectives:

Long-term survival can be obtained in patients with oligometastatic colorectal cancer (CRC) undergoing resection with curative intent. The aim of this study is to evaluate the efficacy and toxicity of high-precision radiotherapy in the treatment of oligometastatic CRC patients who are not amenable for metastasectomy or (further) systemic treatment. The primary objective is to evaluate the metabolic complete response rate by performing PET-CT scan at baseline and 3 months after initiation of radiotherapy. Secondary objectives are progression-free survival, local control rate, overall survival and acute & late toxicity.

Inclusion criteria:

1) Patients with oligometastatic CRC:  5 metastases
2) Patients not amenable for metastasectomy or (further) systemic treatment

Study plan:

A PET-CT scan will be performed to delineate and plan radiotherapy. The treatment is carried out using rotational intensity-modulated radiotherapy (helical tomotherapy or VMAT), delivering a dose of 50 Gy in 10 fractions (5 fractions a week). Three months after the start of radiotherapy, the response will be evaluated by PET-CT.

Number of patients:
Aiming at an overall acceptable and unacceptable complete metabolic response probability of 50% and 30%, the sample size for first and second stage are 7/22 and 17/46, according to Simon two-stage design for phase 2 studies.