The use of blood test trends in cancer detection: a scoping review.

BACKGROUND: Monitoring trends in repeated blood tests might offer opportunities to improve cancer detection. This review aimed to systematically map the existing literature on blood test trends in cancer detection, characterise how these trends have been used in cancer detection approaches, and identify research gaps. METHODS: MEDLINE, Embase, ProQuest Dissertations & Theses Global, and Overton were searched from inception to April 2025 to identify published and unpublished studies investigating pre-diagnostic blood test trends for cancer detection. Screening was performed by four reviewers. Data extraction was conducted independently by two reviewers, with discrepancies resolved through consensus. Data were narratively synthesised to summarise study and patient characteristics, and the blood tests and cancers investigated. Major themes were identified to categorise key research areas and describe how blood test trends have been used in cancer detection. RESULTS: Ninety studies were included. Colorectal and pancreatic cancers were the most commonly studied cancers, with haemoglobin and HbA1c the most frequently investigated blood tests for each, respectively. Studies primarily focused on either the association between blood test trends and cancer (n = 64) or on prediction models incorporating blood test trends to predict cancer risk (n = 26). Additional thematic areas covered by the included studies were: combining trends with other risk factors for cancer (n = 62), implication for practice (n = 58), blood tests trends versus abnormality (n = 40), combination of trends in different blood tests (n = 39), and bias due to informative observation (n = 12). However, evidence for many other cancer types was scarce, and important gaps remain in understanding how blood test trends can be further used for cancer detection, including their predictive value and implementation strategies. CONCLUSION: Evidence to date indicates that blood test trends have been increasingly studied in the context of cancer detection, although knowledge remains fragmented and largely exploratory. Future research should expand to under-studied cancers and examine these trends across a broader range of contexts to better understand their role in cancer detection. REGISTRATION: Open Science Framework https://osf.io/ue8s4 .