Tumoural PDL1 expression, the number of lymphocytes within the tumoural bed (TILs) and the mutational load are the three major predictors. Of interest smokers are usually good responder to immunotherapy because their associated NSCLC have high mutational load thank to tobacco usage. Colon cancer with abnormal MMRs also have high mutational load and respond well to immunotherapy. Patients pre-treated with radiotherapy have better response to immunotherapy thank to increased mutation induced by radiation. Melanoma are associated with very high mutational load to the point that there is no need to test. Attempts to quantitate mutational load has failed because of difficulty to standardize its measurement.