Here, we investigated the two most frequently mutated SWI/SNF genes, ARID1A and SMARCA4. Further, we focused our study on five tumour types (bladder cancer [BC], colorectal cancer [CRC], non-small cell lung cancer [NSCLC], OC and PC), to permit exploration of any association between DDR GAs and clinically relevant immunotherapy biomarkers (PD-L1, TMB) and identification of potential opportunities for combination therapy. The gene discussed is SMARCA4; the disease is breast cancer.