Liquid Biopsy Revolutionizes Breast Cancer Treatment

Choosing the right treatment for breast cancer is often a race against time. While major advances in oncology have significantly improved survival rates, doctors still face a critical challenge: predicting which therapy will work best for each individual patient. A new study suggests that help may come from an unexpected source—a simple blood test.

Researchers at the Institute of Cancer Research (ICR) in London have developed a DNA-based blood test that can predict how well patients with advanced breast cancer will respond to specific treatments, even before therapy begins. The findings point toward a future where cancer treatment is faster, more personalized, and less trial-and-error.

Breast Cancer and the Need for Personalized Treatment

Breast cancer is the most commonly diagnosed cancer worldwide, affecting more than two million people each year. Although treatment options—including chemotherapy, hormone therapy, targeted drugs, and immunotherapy—have expanded dramatically, not all patients benefit equally from the same approach.

Currently, doctors rely on tumor biopsies, imaging, and clinical indicators to guide treatment decisions. However, these methods cannot always predict whether a therapy will be effective, sometimes exposing patients to drugs that offer little benefit while causing significant side effects.

What Is a Liquid Biopsy?

The new test is a form of liquid biopsy, a minimally invasive technique that analyzes fragments of genetic material released into the bloodstream by cancer cells. These fragments, known as circulating tumor DNA (ctDNA), carry information about the cancer’s behavior and genetic makeup.

Unlike traditional biopsies, liquid biopsies can be performed repeatedly with a simple blood draw, making them ideal for monitoring disease progression and treatment response over time .

How the Study Was Conducted

The research team analyzed blood samples from 167 patients with advanced breast cancer. ctDNA levels were measured at two key points: before treatment began and again after four weeks, following one cycle of therapy.

Patients were divided into two groups:

• Group One: Patients whose tumors had specific genetic mutations—such as ESR1, HER2, AKT1, AKT, or PTEN—and who received targeted therapies matched to those mutations.

• Group Two: Patients with triple-negative breast cancer (TNBC), an aggressive subtype accounting for 10–15% of cases globally. These patients received a combination of the PARP inhibitor olaparib and the ATR inhibitor ceralasertib.

ctDNA Levels Strongly Linked to Treatment Outcomes

The results revealed a clear pattern. Patients with low ctDNA levels before treatment were significantly more likely to respond well to therapy than those with higher levels.

In the triple-negative breast cancer group, patients with low ctDNA experienced longer progression-free survival, averaging 10.2 months, compared with 4.4 months for those with higher ctDNA levels. Treatment response rates were also markedly different—40% in the low-ctDNA group versus 9.7% in the high-ctDNA group.

A similar, though slightly weaker, association was observed in patients receiving mutation-matched targeted therapies.

Early Signals Matter: The Four-Week Test

Perhaps most striking were the results from the four-week follow-up blood tests. In both patient groups, individuals whose ctDNA became undetectable after just one treatment cycle experienced substantially better outcomes.

• In the targeted-therapy group, patients with undetectable ctDNA had their cancer controlled for 10.6 months, compared with 3.5 months for those with detectable ctDNA.

• In the triple-negative group, cancer remained under control for 12 months in patients with undetectable ctDNA, compared with 4.3 months in others.

These findings suggest that ctDNA levels can act as an early warning signal, allowing doctors to adjust treatment plans long before traditional scans would reveal whether a therapy is failing.

Why This Could Be a Game Changer

According to Dr. Iseult Browne, clinical research fellow at the ICR and lead author of the study, the ability to predict treatment response early could dramatically improve patient care.

By identifying ineffective treatments quickly, doctors could switch patients to alternative therapies, combination approaches, or clinical trials—potentially improving survival and quality of life. Ongoing trials are now testing whether adapting treatment based on ctDNA results leads to better long-term outcomes.

Implications Beyond Advanced Breast Cancer

While this study focused on advanced breast cancer, experts believe the approach could also be applied to early-stage disease. If validated in larger trials, ctDNA testing could become a routine tool in oncology, guiding treatment decisions across multiple cancer types .

Professor Nicholas Turner, a molecular oncologist at the ICR, notes that liquid biopsies have the potential to make cancer treatment faster, more precise, and more effective, reducing unnecessary toxicity while maximizing benefit.

A Step Toward Smarter Cancer Care

This research highlights a broader shift in medicine—from one-size-fits-all treatment to data-driven, personalized care. While more studies are needed before ctDNA testing becomes standard practice, the evidence suggests that a simple blood test could soon play a central role in determining how breast cancer is treated.

For patients and clinicians alike, that could mean fewer delays, better outcomes, and a clearer path forward in the fight against one of the world’s most common cancers.

References

1. Browne, Iseult, et al. “Circulating Tumour DNA as an Early Predictor of Treatment Response in Advanced Breast Cancer.” Nature Medicine, 2024.

2. Turner, Nicholas C., et al. “Precision Oncology and the Role of Liquid Biopsies.” The Lancet Oncology, vol. 24, no. 3, 2023.

3. Abbosh, Chris, et al. “Phylogenetic ctDNA Analysis Depicts Early-Stage Lung Cancer Evolution.” Nature, vol. 545, 2017.

4. National Cancer Institute. “Liquid Biopsies in Cancer Research.” NIH, 2023.

5. Breast Cancer Now. “Advances in Targeted Treatments for Breast Cancer.” 2024.

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