Caren van Roekel

259 Discussion Besides surgery, other therapeutic options for colorectal cancer liver metastases are ablation (e.g. radiofrequency ablation, microwave ablation, cryoablation, irreversible electroporation), either solely or in combination with resection. There is growing evidence on these techniques, with studies showing similar overall survival rates with these ablative strategies compared with resection (11, 12). Ablative strategies can also be combined with systemic therapy: in the CLOCC trial, patients with unresectable colorectal cancer liver metastases were assigned to systemic treatment alone or systemic treatment plus local treatment by radiofrequency ablation with or without resection. Overall survival was significantly longer in the patients that received combination treatment: median 45.6 months versus 40.5 months in the systemic therapy-alone group (hazard ratio 0.58, 95%CI 0.38-0.88). Progression-free survival was significantly prolonged by almost 7 months in the combined treatment arm (hazard ratio 0.57, 95%CI 0.38-0.85) (13). These findings show that in carefully selected patients, ablative strategies can be a substitute for resection. In the ongoing COLLISION trial, CRC patients with at least one resectable and ablatable hepatic metastasis (up to 3 cm) are randomized between ablation (either radiofrequency ablation or microwave ablation) and resection (14). If ablation proves to be non-inferior compared to resection, this study will change management for many patients. As ablation is associated with less post-procedure morbidity and mortality and a shorter hospital stay, this will have an impact on both patients and clinical costs. For patients with truly unresectable disease, chemotherapy is indicated. Median overall survival for patients treated with chemotherapy is improving, with median survival rates of more than 20 months (15, 16). Most survival gain is caused by improvements in first-line therapies (17). Currently, there are at least nine different types of systemic treatment options for metastatic colorectal cancer (18): • Fluoropyrimidines (including fluorouracil, leucovorin and capecitabine) (by conversion to fluorodeoxyuridine monophosphate, the enzyme thymidylate synthase is inhibited. This leads to inhibition of RNA synthesis and DNA strand breaks, inhibiting cell growth (19)) 10