惡性腫瘤為2016 年臺灣十大死因之第一位，其中女性的乳癌死亡率占女性罹癌死亡率之11.7%；傳統荷爾蒙受體陽性的乳癌，可選擇tamoxifen 或芳香環酶抑制劑。Palbociclib 為全新機轉的細胞週期蛋白依賴性激酶 (cyclin-dependent kinase, CDK) 4/6 抑制劑，可以合併荷爾蒙療法治療婦女雌激素受體陽性、人類上皮細胞生長因子接受器第2 型陰性之晚期或轉移性乳癌。目前已有二大型臨床研究顯示palbociclib和芳香環酶抑制劑或fulvestrant 併用可以顯著延長無惡化存活期；安全性的部分，常見的不良反應為嗜中性白血球低下，但其為可逆性，停藥後可以恢復，因此建議患者於治療過程中需接受血液常規檢查；除了治療乳癌之外，palbociclib 目前尚有應用於其他種類的癌症之臨床試驗，初步結果也顯示有治療益處。

Malignant tumors are ranked on the top of 10 major causes of death in Taiwan in 2016, with female breast cancer mortality rate accounting for 11.7% of all female cancers. Tamoxifen, an aromatase inhibitors, is used to treat estrogen receptor-positive breast cancers. Palbociclib, an unique cyclin-dependent kinase (CDK) inhibitor, is used in combination with hormonal therapy to treat estrogen receptor-positive and human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer. Currently, two major clinical trials showed that the use of palbociclib with an aromatase inhibitor or fulvestrant can prolong the time of patients’ progressionfree survival. Neutropenia is the most common side effect of palbociclib, however,
is reversible after discontinuing the drug. Therefore, patients’ complete blood counts need to be monitored carefully in all patients medicated with a CDK4/6 inhibitors. Apart from treating breast cancer, palbociclib has also shown to have positive results in preliminary clinical trials for other cancers.