Similar, ongoing therapeutical benefit was observed for both breast cancer cases during non-matched treatment modalities; therefore, MTB recommendations, i.e., PARP-inhibitor olaparib for the BRCA2 p.Asn433GlnfsTer18/ATM p.Ser2259TyrfsTer13/CHEK2 p.Ile188Thr-mutated cancer and alpelisib for the PIK3CA p.His1047Arg-mutated cancer, were not clinically translated until time of data cut-off. This evidence concerns the gene CHEK2 and cancer.