A New Era in Breast Cancer Monitoring: Can Blood Tests Warn of Disease Earlier?
One of the hardest questions in breast cancer treatment is knowing, in good time, whether the therapy being used is actually working. Advanced blood tests — liquid biopsy and ctDNA analysis — help answer this question and can signal the disease becoming active again months before imaging does.
June 4, 2026 — How can we tell whether the treatment we use in breast cancer is truly working? A tumor must reach a certain size before it becomes visible on CT or MRI. So if the disease starts again, is it possible to detect it earlier?
In recent years, one of the methods seeking answers to these questions has been advanced blood tests. Liquid biopsy and ctDNA analysis examine tiny fragments of DNA that cancer cells release into the blood, providing additional information about how the disease is progressing.
In the study published in the journal Nature Communications, patients with hormone receptor–positive, HER2-negative metastatic breast cancer were examined. These patients were receiving targeted drugs known as CDK4/6 inhibitors together with endocrine therapy. The researchers monitored circulating tumor DNA in the blood at regular intervals throughout treatment.
What Are Liquid Biopsy and ctDNA?
Liquid biopsy is an examination performed using a blood sample. Cancer cells can release very small fragments of DNA into the blood. These fragments are called circulating tumor DNA, or ctDNA for short. ctDNA analysis can help track how the cancer is responding to treatment.
One of the important aspects of this study is that it looked not only at genetic changes in the cancer, but also at special marks in the tumor DNA called methylation. Methylation-based ctDNA monitoring aims to detect very low levels of tumor traces in the blood more sensitively.
- ctDNA could be detected in the large majority of patients at the start of treatment.
- The disappearance or marked decrease of ctDNA during treatment was associated with a better treatment response.
- An increase in ctDNA levels was regarded as an early warning sign of disease progression or treatment resistance.
Why Does Minimal Residual Disease (MRD) Matter?
- Minimal residual disease (MRD) refers to very small traces of cancer that may remain in the body after treatment and may not yet be visible on CT or MRI.
- Methods such as CT, MRI, and PET/CT are very valuable in breast cancer follow-up; however, the disease sometimes needs to reach a certain size before it can be seen.
- In the study, methylation-based ctDNA monitoring was reported to be able to show molecular signals of disease progression about 6 months before they were detected by imaging.
- This information can help the physician monitor the treatment response more closely and, if necessary, plan additional investigations or a change in treatment.
For this reason, MRD monitoring and liquid biopsy can contribute to following the disease not only through CT, MRI, or PET/CT results, but also through the molecular behavior of the cancer.
What Does This Development Mean for Patients?
Cancer genetic testing, ctDNA analysis, and advanced blood tests can help provide a more personalized assessment for each patient, rather than the same follow-up approach for everyone.
- The effect of the current treatment can be monitored more closely.
- Molecular signs of the disease becoming active again can be noticed before CT or MRI findings.
- They can provide additional information about the development of resistance during targeted therapies such as CDK4/6 inhibitors.
- The physician can, when necessary, reassess the frequency of follow-up or the treatment plan.
- This approach is an important advance in terms of personalized cancer treatment and targeted cancer treatment.
💬 Expert Opinion
The goal in breast cancer treatment is not only to treat the disease, but to assess the effect of treatment at the right time. By allowing us to read the molecular behavior of the disease before imaging findings appear, liquid biopsy and ctDNA monitoring can help us make more individualized decisions.
Conclusion: Toward More Precise and Personalized Monitoring
In breast cancer treatment, the goal is not only to treat the disease but to assess the effect of treatment at the right time. Monitoring with liquid biopsy, ctDNA, and minimal residual disease can provide more precise information about the course of the disease, especially in metastatic breast cancer.
Even so, it should be kept in mind that these tests may not be suitable for every patient. The most accurate decision should be made by considering scientific data, the patient’s individual characteristics, and the physician’s clinical judgment together.