Understanding Minimal Residual Disease (MRD) and Liquid Biopsy in Cancer Care

With the increased sensitivity of the recent tools, it is now easier to test for these small traces of disease. One of the most validated approaches is liquid biopsy testing, where a simple blood test can measure cancer-related material traces and consequently provide a better and more personalised view of the patient’s course of disease, without needing to conduct multiple invasive procedures.

What Is Minimal Residual Disease (MRD)?

Minimal residual disease describes cancer cells that persist in the human body, even when a patient is otherwise in remission. People discuss MRD mostly in relation to blood cancers or haematologic malignancies, such as leukaemia, lymphoma, and myeloma. Nevertheless, new research demonstrates that MRD bears relevance in some solid tumours that can benefit from the application of sensitive measures to detect very small amounts of disease.

The presence of MRD may indicate a higher risk of recurrence. When MRD is not present, it is generally an indication that the treatment is working, but patients need close follow-up visits regardless.

Minimal residual disease testing is valuable for all patients and cancer types because each patient’s cancer and response to treatment are different. These tests help clinicians assess treatment regimens, whether to consider additional therapy, and provide patients with a sense of assurance in monitoring their progress. 

Currently we have 2 types of technologies available.

1. Gene Panel Liquid biopsy such as Guardant Reveal.
2. Tissue informed liquid biopsy such as Signatera 

Liquid Biopsy Technology

A liquid biopsy is a simple blood draw that tests for microscopic evidence of cancer, such as circulating tumour DNA (ctDNA). Cancer cells release ctDNA into the bloodstream upon dying. Doctors analyse this material to assess the patient’s cancer status without the need for a sample of tissue.

Liquid biopsy technology allows specialists to monitor changes happening inside the body in real time. This is very different from traditional biopsies, which can only show what was happening at the moment tissue was removed. Liquid biopsies are also less invasive, which is more comfortable for patients without the need for surgery and recovery.

There are two main scientific methodologies widely employed:

• PCR-based sequencing, which is highly sensitive to specific genetic changes
• Next-generation sequencing (NGS), which can screen a wider array of gene alterations

Both contribute to a more accurate MRD detection, while they also allow for a richer understanding of cancer behaviour over time. Patients benefit immediately from increased precision, more firmly counselling doctors when adjusting treatment.

Clinical Applications of MRD and Liquid Biopsy

MRD and liquid biopsy tools are taking on an increasingly paramount role in both blood cancers and some solid tumours. Doctors can use these tools to monitor how well treatment is working, helping patients feel more informed throughout their care journey. For example, in some liquid tumours, clinical teams now use MRD to track early treatment response long before symptoms or scans change.

In many cancers, MRD helps guide decisions about additional therapy. This provides significant benefits after major therapies, including chemotherapy, radiotherapy, or stem cell transplantation. The reduction of MRD counts can indicate effective treatment. On the other hand, if levels increase, a doctor may intervene more quickly to prevent relapse.

Liquid biopsy in cancer care also supports important decisions about adjuvant therapy. Patients who appear cancer-free on imaging might still have low levels of disease that require further treatment. Detecting this early can improve long-term outcomes and offer reassurance that care is being personalised.

These tools enhance the accuracy of cancer monitoring and can assist clinicians in developing clearer, reliable treatment pathways. In many patients, this is emotional reassurance at a time when all is uncertain.

Challenges and Limitations

While there have been great advances in MRD detection, it is still a developing field, and it is important for patients to understand the shortcomings. One challenge involves test sensitivity, which determines how well a test can spot the smallest traces of disease. Another issue is specificity, which ensures tests correctly identify cancer material without creating false positives or negatives.

There is also a new need for standardisation. Why? There can be slight variations in results if laboratories use different equipment or techniques. The best practice is always for a patient to have an in-depth discussion regarding results with a specialist who can offer perspective in the context of their care.

Liquid biopsy cancer screening is not yet a replacement for traditional imaging studies or physical exams; they work in parallel to each other to give a fuller picture. Researchers continue to refine liquid biopsy’s current technology and clinical applications all over the world, and surveillance is already improving for accuracy and reliability every year.

Future Directions

The future of MRD is intimately connected with the future of personalised medicine. Scientists are creating even more sensitive tools that might be capable of detecting cancer cells even earlier than we can today. Over the next few years, liquid biopsy in cancer is likely going to be much more than just a diagnostic tool. Still, it may help predict treatment response longitudinally before therapy initiation.

Emerging technologies are aiming to make liquid biopsies more readily available for routine care, potentially giving patients a quicker, easier option compared to standard tests. There are also encouraging advancements in combining MRD with artificial intelligence technologies to predict relapse trends more accurately.

A number of studies are also looking into the roles of liquid biopsies as part of clinical trials. These studies will help assess and evolve treatment plans for patients in real time and limit the number of invasive hospital-based procedures required. Eventually, we see MRD and liquid biopsies emerging as the hub of precision oncology, driving treatment decisions for each patient’s specific cancer biology.

Wrapping Up

Minimal residual disease is a key concept that physicians use to study cancer behaviour in relation to treatment and post-treatment work-up. With the use of tools such as liquid biopsy, patients are now offered more nuanced and easier methods of monitoring their treatment. It certainly helps to alleviate uncertainty and make decisions more personalised at every level of care.
If you or a loved one has questions about MRD testing or liquid biopsy approaches to monitoring, a cancer expert will be able to help guide you based on your individual situation. The combination of science and compassion will continue to help build a new era of more accurate cancer monitoring and improved patient outcomes.