Diagnosing Cancer Through Liquid Biopsy

Diagnosing cancer through blood samples in this way could improve access to cancer testing in primary care settings and aid earlier cancer detection and diagnosis, including potentially in asymptomatic and at-risk groups. That could enable quicker referrals for staging and grading cancers and thus timely access to treatments. Blood samples could also potentially be collected more often than tumour biopsies can be carried out, and could also be more acceptable for patients and improve their experience.

In theory, blood-based tests could thus help with tackling bottlenecks for hospital scans. However, if more people are diagnosed through liquid biopsy and if these tests do not replace imaging but help triage or complement it, there could be an increase in demand for imaging to follow up.

“Blood-based tests may enable pan-cancer diagnostics, which can potentially detect multiple cancers based on a single blood sample.”

Blood-based tests may also enable pan-cancer diagnostics, which can potentially detect multiple cancers based on a single blood sample. These have had some promising clinical trial results, and prompted growing interest in testing wider-scale adoption in health systems. Other technologies in development can capture live circulating tumour cells (CTCs). CTCs allow additional analysis of cancers because replication of cells is used to understand mutations and metastasis mechanisms, new and novel therapy design, and therapy testing. Liquid biopsy is also being considered for ongoing follow-up monitoring, such as testing for the presence of cancer after chemotherapy or surgery.

Challenges for Routine Use of Liquid Biopsy

What needs to be done to prepare health systems for routine use of liquid biopsy? The possibilities are exciting, but for liquid biopsy to be routinely used in the UK National Health System (NHS), four key challenges will need to be addressed.

1. Test Accuracy and Appropriate Use:

   First, there are still issues to overcome related to test accuracy and when testing is appropriate, balancing test utility versus risk of errors or overtreatment. There are trade-offs to contend with between diagnostic sensitivity (how likely it is that a test will produce a positive result in the case of a cancer) and diagnostic specificity (likelihood of wrongly identifying a cancer when it is not present). Even a small percentage of false positives or false negatives can put pressure on services.

2. Infrastructure:

   Second, routine use of these tests requires appropriate infrastructure to be in place, from testing laboratories to wider health systems capacity for liquid biopsy. The United Kingdom has genomic testing laboratories, but these facilities can be located far away from services where samples are taken from patients. As ctDNA has a short shelf-life, timely sample processing is key. Transport times and storage logistics can create challenges in their own right.

3. Skilled Workforce:

   Third, the NHS and diagnostic labs must have enough appropriately trained and skilled staff, supported with clear guidance and quality control processes. A skilled workforce will be needed to collect, prepare, store, and process blood samples, as well as to analyse results, especially lab scientists and bioinformaticians.

4. Evidence of Cost Effectiveness:

   Fourth, decisionmakers need to see evidence of real-world cost effectiveness. Although there are some promising insights from clinical trials, real-world evidence on the cost effectiveness of liquid biopsy tests for use in oncology is still limited.

Conclusion

Based on trial data, some tests demonstrate promising results for the identification of early-stage cancers. They range in sensitivity at stage 1 cancer at 16.8–99 percent, at stage 2 at 40.4–97 percent, at stage 3 at 62–99 percent, and at stage 4 at 57–98 percent. Trial data also show tests range in specificity at 58–>99 percent. In addition, a recent systematic literature review on the health economic evidence for liquid biopsy assays in cancer found that liquid biopsy was found to be cost-effective in 75 percent of studies.