Patients with metastatic breast cancer may respond well to treatment and metastases can remain stable for several years. Despite personalised medicine being increasingly used for diagnosis and treatment, follow-up still include radiological response evaluation every 3-4 months, which renders a significant number of 'unnecessary' exams for patients with long-term stable disease. Increasing evidence indicates that tumour markers such as circulating tumour DNA (ctDNA), thymidine kinase 1 (TK1) and cancer antigen 15-3 (CA15-3) may be useful for disease monitoring in the metastatic setting. However, algorithms that accurately define the time-points at which imaging can be foregone or reinstituted when progression is forecast, have not been developed. This study will measure ctDNA, TK1 and CA15-3 at all imaging time-points. The primary aim is to develop an algorithm based on these biomarkers, alone or in combination, that with sufficient specificity and sensitivity can advise whether a scan can be safely omitted at a specific time-point, for patients with MBC receiving first line therapy with AI plus cyclin dependent kinase 4/6 inhibitor (CDK4/6i). Additional samples will be stored such that novel biomarkers can also be tested in future. The cost-effectiveness of using the devised biomarker protocol will be evaluated.
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Change in blood levels of ctDNA, CA15-3 and TK-1 assays from baseline to disease progression
Timeframe: 3-5 years