653 Background: Complete metastasectomy provides a real chance for long-term survival in patients with oligometastatic colorectal cancer (CRC). For patients who are not amenable for metastasectomy, we demonstrated in a previous study the feasibility of moderately hypofractionated intensity-modulated and image-guided radiotherapy (RT) by helical tomotherapy. Aiming at higher response rates, we evaluated in this study helical tomotherapy delivering 50 Gy in daily fractions of 5 Gy. Methods: Inoperable CRC patients with ≤ 5 metastases were enrolled. No limitations concerning dimension or localization of the metastases were imposed. Whole body PET-CT was performed at baseline and 3 months after the initiation of RT to evaluate the metabolic response rate according to PERCIST v 1.0. Side effects were scored using the NCI CTC AE v 3.0 scale. Results: We report the results of the first 22 patients. Thirteen patients (59%) received previous chemotherapy for metastatic disease, displaying residual (n=7) or progressive (n=6) metabolic active metastatic disease at time of inclusion. A total of 51 metastases were treated. Most common sites were the lung, liver and lymphnodes. One patient (5%) experienced grade 3 dysphagia; 2 patients (9%) and 1 patient (5%) grade 2 dysphagia and diarrhea, respectively. Twenty patients were evaluated by post-treatment PET-CT. Five and 6 patients achieved a complete and partial metabolic response, resulting in an overall metabolic response rate of 55%. At a median follow-up of 11 months, 17 patients (77%) developed progressive disease, of which 3 isolated local progression. Five patients (23%) are in remission in all irradiated areas without evidence of distant recurrence. Interestingly, those 5 patients received previous chemotherapy with residual oligometastatic disease at time of inclusion. Conclusions: Ten fractions of 5 Gy resulted in a promising 55% metabolic response rate with limited toxicity. Helical tomotherapy is an attractive modality in the multidisciplinary approach of oligometastatic CRC, more specifically in the consolidation of residual and inoperable oligometastatic disease in patients previously treated with chemotherapy.
Diagnostic accuracy of whole-body MRI versus standard imaging pathways for metastatic disease in newly diagnosed colorectal cancer: the prospective Streamline C trial