Can a blood test detect cancer

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Can a Blood Test Detect Cancer?

Introduction to Blood Tests for Cancer Detection

Blood tests for cancer detection have emerged as a promising tool for early diagnosis, which is crucial for effective treatment and improved survival rates. These tests aim to identify molecular markers, such as DNA mutations, protein biomarkers, and methylation patterns, that are indicative of cancer presence.

Multicancer Blood Tests and Their Efficacy

Feasibility and Safety of Multicancer Blood Tests

A large feasibility study involving 10,006 women demonstrated that a multicancer blood test, combined with positron emission tomography-computed tomography (PET-CT), could detect various cancers at an early stage. The study found that the blood test detected 26 cancers, with a specificity of 98.9% and a positive predictive value (PPV) of 19.4%. When combined with PET-CT, the specificity and PPV increased to 99.6% and 28.3%, respectively. Importantly, the test did not lead to a significant number of unnecessary follow-up procedures, indicating its safety and potential for routine clinical use.

CancerSEEK: A Multi-Analyte Blood Test

The CancerSEEK test, which assesses circulating protein biomarkers and tumor-specific mutations in DNA, has shown promising results. In a study involving 1,000 cancer patients and 850 healthy controls, CancerSEEK detected cancer with a sensitivity ranging from 69% to 98% depending on the cancer type, and a specificity of 99%. This test was particularly effective for cancers such as ovary, liver, stomach, pancreas, and esophagus, for which no standard screening tests are available.

Specific Blood Tests for Colorectal Cancer

Full Blood Count (FBC) and Colorectal Cancer

A systematic review and meta-analysis of the Full Blood Count (FBC) test identified several components, such as red blood cells, hemoglobin, and white blood cell count, that are associated with colorectal cancer. Thirteen FBC-based prediction models were developed, showing varying degrees of accuracy, with c-statistics ranging from 0.72 to 0.91. These models indicate that FBC components could be useful for early detection and referral for colorectal cancer.

Faecal Occult Blood Test (FOBT)

The faecal occult blood test (FOBT) has been widely used for colorectal cancer screening. A review of randomized controlled trials involving over 320,000 participants showed that biennial screening with FOBT reduced colorectal cancer mortality by 15% to 25%, depending on screening attendance. This test highlights the potential of non-invasive methods for reducing cancer mortality.

Non-Invasive Early Detection Methods

PanSeer: Early Detection Before Conventional Diagnosis

The PanSeer test, which detects cancer through circulating tumor DNA methylation, has shown the ability to identify cancer up to four years before conventional diagnosis. In a study involving 605 asymptomatic individuals, PanSeer detected five common types of cancer with a sensitivity of 95% and a specificity of 96%. This suggests that non-invasive blood tests can significantly advance early cancer detection.

Accuracy of Tumor Origin Detection

A meta-analysis of cell-free DNA (cfDNA)-based multi-cancer early detection (MCED) tests found that these tests could accurately determine the tissue of origin in 79% of cases. The accuracy varied across cancer types, with colorectal cancers showing the highest accuracy and liver & bile duct cancers the lowest. This ability to localize the tumor origin is crucial for guiding appropriate treatment .

Conclusion

Blood tests for cancer detection, including multicancer tests like CancerSEEK and PanSeer, as well as specific tests for colorectal cancer, have shown significant promise in early diagnosis. These tests can detect various cancers with high specificity and sensitivity, often before conventional methods. As research progresses, these non-invasive tests could become integral to routine cancer screening, improving early detection and treatment outcomes.