Fong Mun Yee, Wong FY, Lim Hsuen Elaine

Use of cyclin-dependent kinase (CDK) 4/6 inhibitors in treatment of metastatic breast cancer patients in Singapore

Abstract Disclosures

Abstract
Background: Breast cancer is the most prevalent cancer among the female population in Singapore. Notably, there are 11,232 cases reported in the period between 2014 and 2018, accounting for 29.3% of the total cancer incidence in Singapore females. Hormone receptor (HR)-positive breast cancers, characterised by the presence of oestrogen or progesterone receptor expression, account for approximately 75% of new breast cancer diagnoses. Endocrine therapy remains the backbone of the treatment of HR–positive patients with breast cancer. However, almost 50% of the patients with metastatic breast cancers developed resistance to the hormonal therapy received, and subsequent disease progression remains a major challenge to treatment in this group of patients. In order to improve treatment efficacy, the development of cyclin-dependent kinase 4/6 (CDK4/6) inhibitors has played an important role in the treatment of metastatic breast cancer. 
CDK4/6 inhibitors are a class of drugs used to target the CDK4/6 pathway, which was shown to be overactive in various types of cancers, including breast cancer. CDK4/6 inhibitors induce cell cycle arrest by blocking the transition from G1 to S phase of cell cycle activation. Three available agents in the group include palbociclib, ribociclib, and abemaciclib. CDK4/6 inhibitors in combination with hormonal therapy (aromatase inhibitor or fulvestrant) are FDA approved as the first- or second-line treatment of HR–positive, ERBB2 (formerly HER2)–negative metastatic breast cancer. With increasing use of this group of drugs as standard care of treatment and their high cost, it is essential to assess the treatment value and clinical outcomes among the local Singapore population.

Hypothesis: This retrospective study aims to investigate the clinical efficacy and treatment cost of CDK inhibitors in metastatic breast cancer patients in Singapore.

Methodology: Retrospective study will utilize demographic, clinical and billing information extracted from electronic medical records.  Records of patients receiving CDK4/6 inhibitors will be used to do a comparison with patients who did not receive CDK 4/6 inhibitors.

References:
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3.	Loke L, Lee SC, Pearce F, Ng K, Aziz MIA. Cost-effectiveness of ribociclib as initial treatment for premenopausal women with advanced breast cancer in Singapore. Cancer Rep (Hoboken). 2021 Feb;4(1):e1308. doi: 10.1002/cnr2.1308. Epub 2020 Oct 21. PMID: 33085843.  
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Joint Breast Cancer Registry Singapore