To assess whether the previously reported better prognosis of MMR‐deficient tumours8 might be explained by their association with B2M mutations, we compared the recurrence rate in dMMR B2M‐wild‐type tumours with that in all MMR‐proficient tumours in the QUASAR trial, and found no significant difference overall or in analyses restricted to right‐sided colon tumours, where most dMMR tumours arise (Figure 4). This evidence concerns the gene B2M and digestive system neoplasm.