Arm B: ctDNA guided ACT
For patients randomised to ctDNA guided ACT, the post-operative (Month 0) blood sample will be processed in real time and the result will be published on the Guardant Health online portal. The recommended SOC chemotherapy regimen will continue to be used in patients who are ctDNA positive post-operatively, whilst ACT will be de-escalated in those who are ctDNA negative. Where 3 months of CAPOX has been recommended, treatment will be de-escalated to 3 months of capecitabine alone, and where 6 months of capecitabine monotherapy has been recommended, treatment will be de-escalated to no chemotherapy. Patients who are ctDNA negative post-operatively and have their chemotherapy de-escalated (Fig. De-escalation/escalation strategy in ctDNA negative group in the ctDNA-guided arm