Phase II study of helical tomotherapy for oligometastatic colorectal cancer

Background: To evaluate the efficacy and toxicity of helical tomotherapy in the treatment of oligometastatic colorectal cancer (CRC) patients who were not amenable for metastasectomy and/or (further) systemic treatment. Patients and methods: CRC patients with five or less metastases were enrolled. No limitations concerning dimension or localization of the metastases were imposed. Patients were treated with intensity-modulated and image-guided radiotherapy using helical tomotherapy, delivering a total dose of 40 Gy in fractions of 4 Gy. Positron emission tomography-computed tomography (PET-CT) was carried out at baseline and 3 months after the initiation of radiotherapy to evaluate the metabolic response rate according to PET Response Criteria in Solid Tumors (PERCIST) version 1.0. Side-effects were scored using National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTC AE) version 3.0. Results: Twenty-three patients were enrolled. A total of 52 metastases were treated. One patient (4%) experienced grade 3 vomiting; two patients (9%) grade 2 diarrhea and dysphagia, respectively. Twenty-two patients were evaluated by post-treatment PET-CT. Five (23%) and seven patients (32%) achieved a complete and partial metabolic response, respectively, resulting in an overall metabolic response rate of 55%. The actuarial 1-year local control, progression-free survival, and overall survival were 54%, 25% and 86%, respectively. Conclusion: The use of helical tomotherapy in oligometastatic CRC patients resulted in a promising metabolic response rate of 55%.