PIK3R1 and neoplasm: Oncogenic alterations in the PI3K pathway genes (namely PIK3CA, PIK3R1, PIK3R2, ATK1, AKT2 and MTOR) were detected in 62% and 50% of patients in C1 and C2, respectively (Fig. 3). A tumour mutation burden (TMB) score of >20% was considered high.