Stage 4 breast cancer is often discussed through the language of challenge. That is understandable. But the story of stage 4 breast cancer is not standing still.

Treatment has become more biologically specific. More therapies are shaped by receptor status, genomic alterations, previous treatment and individual goals. Research is also asking better questions about resistance, treatment sequencing, quality of life and how people can access trials and new options.
For people living with stage 4 breast cancer, the aim is not just longer survival. It is also more time with an acceptable quality of life, fewer avoidable side effects, clearer information and care that reflects what matters to the person as well as the disease.

Stage 4 breast cancer is not one situation
The term describes the extent of disease but not the biological condition. Treatment decisions depend on factors including hormone receptor status, HER2 status, previous treatment, disease location, symptoms, general health and patient preferences. The 2026 ESMO Clinical Practice Guideline for metastatic breast cancer covers diagnosis, staging, risk assessment, treatment, disease monitoring and the patient perspective. [1] That breadth matters. Different people will need different treatment options depending on a myriad of factors. This is why stage 4 breast cancer cannot be reduced to a single pathway.

Progress is increasingly biomarker-led
Stage 4 breast cancer treatment has changed because the disease is increasingly divided into biologically defined groups.
Biomarkers can help identify whether a treatment is relevant for a particular person or tumour. ASCO guidance addresses biomarkers including hormone receptor and HER2 status, germline BRCA1 and BRCA2, PIK3CA, ESR1, PD-L1, mismatch repair deficiency, tumour mutational burden and NTRK. [2]
This does not mean every biomarker applies to every person. It means treatment decisions increasingly depend on asking a specific question in a specific setting.

The wider message is clear. Breast cancer biology can change under treatment pressure. What’s needed are methods that can help characterise disease at relevant points in the care journey.

More options create new questions
Progress in stage 4 breast cancer is not only about adding more drugs. It also creates new questions about which treatment should be used first, what should follow after progression, how efficacy should be balanced with toxicity and quality of life, and which biomarkers are ready for clinical use.
Antibody-drug conjugates are a good example. ESMO Breast Cancer 2026 highlighted that these therapies have changed the management of metastatic breast cancer, while data to guide optimal sequencing remains limited. [3,4]

This is a responsible way to talk about innovation. It recognises progress without pretending that every practical question has already been answered.

Liquid biopsy research may help study change over time
Stage 4 breast cancer is often treated over multiple lines of therapy. The disease may adapt, respond, stabilise or progress. This makes change over time an important research question.

Liquid biopsy approaches are being studied because tumour-derived material can sometimes be found in blood or other bodily fluids. [5] This might include circulating tumour DNA, circulating tumour cells and other tumour-associated material.

Circulating tumour DNA can provide molecular information from tumour-derived DNA fragments. [6] Circulating tumour cells are intact tumour cells in the bloodstream. [7] Each may answer different research questions and require different evidence standards.

ASCO’s 2026 guideline on circulating tumour DNA stresses that testing should be used within evidence-based clinical contexts and that recommendations depend on tumour type, setting and intended use. ASCO’s metastatic breast cancer biomarker guideline states that there is insufficient data to recommend routine use of circulating tumour DNA or circulating tumour cells to monitor response to therapy in metastatic breast cancer. [2]

For us, that boundary is important. Frontier Diagnostics is developing Sentinel qCTC™, an investigational platform intended to explore the characterisation of intact circulating tumour cells. This is a research and development statement, not a clinical claim.

The research opportunity is to understand whether intact circulating tumour cell information can contribute to future studies of tumour biology, heterogeneity and change over time. The evidence pathway must remain rigorous.

Equity determines who benefits from progress
Innovation only fulfils its promise when people can access it.

For stage 4 breast cancer, access can include timely diagnosis of recurrence, biomarker testing, specialist oncology care, symptom support, palliative care, clinical trials, new medicines and trusted information.

Patient organisations have a vital role in this conversation. Make 2nds Count is a UK-wide patient and family-focused charity for people affected by secondary, or metastatic, breast cancer. Its work includes research, awareness, support and education, as well as the only patient-focused conference in the UK for secondary breast cancer, held this year in Liverpool. [8]

People living with stage 4 breast cancer often need more than treatment information. They may need help understanding terminology, trial options, side effects, scan results, work, family conversations and the emotional reality of living with incurable disease, as well as the connection, which can only come from being with other women (or men) who have a similar lived experience.

A democratised future for cancer diagnostics cannot focus only on technical performance. It must also consider who gets tested, who understands the result, who can act on it and who may be left behind.

A grounded form of hope
Hope in stage 4 breast cancer should be grounded.

It should never suggest that every advance applies to every person. It should never allude to or imply cure where cure is not the expected outcome. It should never treat trial results as if they are already available to all patients in all health systems.

But it should recognise real movement.

More treatments are being developed around tumour biology. More research is focused on resistance and sequencing. Liquid biopsy and cellular analysis are expanding the questions researchers can ask. Patient advocates are shaping priorities and pushing for better access. Charities and communities are connecting those with lived experience.

That is the space where progress, possibility and equity meet.

At Frontier Diagnostics, our long-term vision is to contribute to building a future to democratise real-time cancer diagnostics for everyone, everywhere. In stage 4 breast cancer, that vision will mean working carefully and responsibly towards better biological insight that could, with the right evidence, support future research and more informed pathways.

Stage 4 breast cancer remains a profound clinical and personal challenge. It is also an area of active progress.
The task now is to ensure that progress is responsible, evidence-led and designed to reach everyone.

Sentinel qCTC™ is an investigational technology platform undergoing development at Frontier Diagnostics Ltd. The platform has not reached design freeze and has not been submitted for regulatory review under IVDR (EU) 2017/746, UK MDR 2002, or FDA 21 CFR Part 809. It is not approved, cleared, or validated for diagnostic, clinical, or commercial research use. All scientific content relating to Sentinel qCTC™ describes developmental aims and does not constitute performance claims.

Sources
1. European Society for Medical Oncology. ESMO Clinical Practice
2. Henry NL, et al. Biomarkers for Systemic Therapy in Metastatic Breast Cancer: ASCO Guideline Update. Journal of Clinical Oncology. 2022. : Metastatic Breast Cancer. 29 May 2026.
3. ESMO Daily Reporter. Sustained quality-of-life benefits reported with first-line antibody-drug conjugate in triple-negative breast cancer. 13 May 2026.
4. ESMO Daily Reporter. How to sequence antibody-drug conjugates in metastatic breast cancer? Target switching alone may not be the answer. 8 May 2026.
5. Venkataraman J, et al. Liquid biopsy in breast cancer: a practical guide for surgeons. Gland Surgery. 2025.
6. Lockwood CM, et al. Circulating Tumor DNA Testing in Solid Tumors and Lymphoma: ASCO Guideline. JCO Oncology Practice. 2026.
7. Thomas-Bonafos T, et al. Circulating tumor cells in breast cancer: clinical validity and utility. npj Breast Cancer. 2024.
8. Make 2nds Count. About Us. Accessed 15 July 2026.

In 1903, the Wright brothers made the first powered flight. For the first few decades of aviation, maintenance was largely reactive – inspect the aircraft, fix what’s broken, fly again. As aircraft became more complex and the consequences of failure more sever, this approach became untenable. The industry moved, gradually and then decisively, from reactive, to preventative, to predictive and finally to continuous monitoring – tracking the condition of critical systems in real time, detecting the early signal pf a problem before it becomes a catastrophic one.

Formula 1 followed a similar path. So did manufacturing, energy and shipping. Across industry after industry, the shift from “fix it when it’s broken” periodic inspection to continuous monitoring produced the same result: fewer failiures, earlier intervention, better outcomes.

Medicine has been slower to make this transition. And in oncology, the gap between where monitoring currently sits and where it could be is one of the most significant unresolved challenges in cancer care. Of course, this simplified analogy ignores the complex journey the aviation industry took to make this a reality. Similarly, in oncology, the clinical, regulatory and pathway infrastructure required to deliver on continuous monitoring still being built- just as the airworthiness regulatory framework was a pre-requisite for aviation’s shift.

What periodic inspection looks like in cancer care
When a patient finishes a course of breast cancer treatment-surgery, chemotherapy, radiotherapy, or a combination – they enter a surveillance phase. The structure of that surveillance varies by cancer type, treatment history and clinical protocol. In advanced cases, it looks something like this: a review appointment every three to six months, imaging at defined intervals, blood tests as indicated. In Stage 3 or less, this might look like an annual mammogram and a phone number to an answering machine.

Such surveillance can be valuable. It is, however, not sufficient.

The problem is not that clinicians are not paying attention. The problem is that the tools being used are designed to detect change once it has become structurally visible. A scan shows a mass that has grown large enough to be seen. A clinical examination identified symptoms that have already developed. By the time these tools detect a problem, the biology has often been active for some time.

In a patient who has completed cancer treatment, there is currently no routine way to know what is happening biologically between appointments or even sometimes if that patient is indeed in remission. The period between reviews is, in a meaningful sense, a monitoring gap.

Why continuous monitoring changes the landscape
The case for continuous monitoring in cancer care is the same as the case for it in every other field where it has been adopted: earlier detection of change leads to earlier intervention, and earlier intervention leads to better outcomes.

In oncology, the evidence for this is clear. Caner detected at an earlier stage is associated with better survival across almost every tumour type. Recurrence detected earlier means more treatment options, more time and in many cases a fundamentally different clinical trajectory for the patient.

The question is not whether earlier detection matters. The question is how to achieve it without placing an unacceptable burden on patients or healthcare systems.

Where liquid biopsy fits
Liquid biopsy- the detection and analysis of cancer-related material circulating in the bloodstream- is one of the most promising tools for closing the monitoring gap. Unlike imaging, it does not require specialist equipment at the point of care. Unlike a tissue biopsy, it does not require an invasive procedure. A blood draw, processed in a laboratory, could be repeated at regular intervals with minimal burden to the patient.

Circulating tumour cell (CTC) technology is one of the most developed forms of liquid biopsy. CTCs are whole cancer cells that shed from a. tumour into the bloodstream. Their presence, their number, their characteristics and the way this can change over time could provide a biological signal – to be tracked longitudinally- not just at a single point in time, but continuously across the course of treatment and into the surveillance period that follows.

This is not the same as a real-time continuous monitor. A blood test every two or three months is not equivalent to the second by second telemetry of a Formula 1 care. But it is a fundamentally different approach from a scan every six months – and for many patients, it represents a meaningful shift in what clinical monitoring can achieve.

The barriers to wider adoption- reputation
CTC technology has had a rocky start- and legacy systems have not managed to live up to the initial promise. However this is changing- CTC technology is reinventing itself and solving many of the sticky issues from legacy systems.

In other words, these are solvable problems. They are being worked on. But there are the reason that a technology with genuine clinical utility has not yet reached patients who could benefit from it.

Where Frontier Diagnostics fits in
At Frontier Diagnostics, our focus is circulating tumour cell technology- analysis that provides the richest biological signal from a blood sample. We are working to make CTC testing accurate, accessible, and clinically actionable for the patients and healthcare professionals who need it.

Our Sentinel qCTC platform analyses living, intact circulating tumour cells from a routine blood draw, providing a biological characterisation that gives beyond simple enumeration. Sentinel qCTC, Frontier’s CTC technology platform, is currently for Research Use Only. It is not approved or cleared for clinical diagnostic use.

The monitoring gap in cancer care is real. The technology to begin closing it exists. Making that transition happen is the work we are committed to delivering.