CD8A and cancer: Case reports have described favourable treatment outcomes from the application of PD-1 blockade in path_POLE cancers.15 33 Furthermore, recent trials have explored the application of PD-1 blockade in MMRd cancers, reporting positive results.20 21 34 35 The best treatment response was seen in those tumours with the highest CD8+T cell numbers; specifically, high CD8+T cell densities (cells/mm2) within the tumour core.