Therefore, we focused on common, well-known 5 proteins of DNMT family, 3 proteins of HDAC family, 15 proteins of PRDM family, and 8 proteins of PRMT family to discover an effective prognostic or predictive factor focusing on epigenetic processing of breast cancer in chemotherapy and radiotherapy settings using hierarchical agglomerative clustering analysis. The gene discussed is HDAC9; the disease is breast cancer.