A composition, combination, and composition comprising a CDK4/6 inhibitor of formula D in combination with a selective estrogen receptor downregulator of formula A, formula B or formula C, which is advantageous for the treatment of abnormal cell proliferation, including cancer or tumors. A method comprising administering them. [Selection diagram] Fig. 12C癌又は腫瘍を含む異常な細胞増殖の治療に有利な式A、式B又は式Cの選択的エストロゲン受容体ダウンレギュレーターと併せた式DのCDK4/6阻害剤を含む、組成物、組み合わせ、及びそれらを投与することを含む方法。【選択図】図12C