Simple Blood Test Predicts Best Breast Cancer Treatments

A groundbreaking study has revealed that a simple blood test can predict how effectively breast cancer patients will respond to various treatments. Developed by researchers at the Institute of Cancer Research in London, this innovative DNA blood test offers a promising approach to personalizing cancer care, potentially improving outcomes for millions of patients worldwide.

Breast cancer remains the most prevalent cancer globally, with over 2 million new diagnoses each year. Despite advancements in treatment, determining the most suitable options for patients has often been challenging. The newly designed liquid biopsy analyzes circulating tumor DNA (ctDNA) in the blood, providing insights into a patient’s likelihood of responding to specific therapies before treatment begins.

The study involved 167 patients with advanced breast cancer, who were divided into two groups based on their cancer types and genetic mutations. The first group included patients with mutations such as ESR1, HER2, AKT1, and PTEN, who received targeted treatments tailored to their genetic profiles. The second group consisted of patients with triple-negative breast cancer—an aggressive variant that comprises 10-15% of global cases and lacks targetable mutations—who were treated with a combination of the PARP inhibitor olarparib and the ATR inhibitor ceralasertib.

The researchers measured ctDNA levels before treatment commenced and again four weeks later, after one treatment cycle. They found a strong correlation between low ctDNA levels at the start of treatment and positive treatment responses. For patients in the second group, those with low ctDNA levels experienced a significant improvement in progression-free survival—averaging 10.2 months compared to 4.4 months for those with higher ctDNA levels. Remarkably, 40% of patients with low ctDNA saw their tumors shrink or disappear, in contrast to just 9.7% among those with elevated levels.

After four weeks of treatment, patients in the first group who had undetectable ctDNA levels exhibited notably better outcomes, maintaining progression-free survival for 10.6 months versus 3.5 months for those with detectable levels. Similarly, in the second group, patients whose ctDNA was no longer detectable after four weeks had their cancer controlled for an average of 12 months, while those with detectable ctDNA managed only 4.3 months.

Dr. Iseult Browne, a clinical research fellow at the ICR and the study’s lead author, emphasized the significance of these findings: “Our study shows that a simple blood test measuring circulating tumor DNA can provide an early prediction of whether a patient’s breast cancer will respond to treatment. Knowing this at the earliest stage means that we can avoid giving patients drugs that won’t work and provide them with alternatives before their cancer has a chance to grow.”

The study was funded by Breast Cancer Now, Cancer Research UK, the NIHR Biomedical Research Centre at the Royal Marsden NHS Foundation Trust, and the ICR. The research supports the potential of ctDNA as a non-invasive biomarker for predicting patient outcomes and monitoring therapy responses.

Prof. Nicholas Turner, a professor of molecular oncology at the ICR and a consultant medical oncologist at the Royal Marsden, noted that while this research focused on advanced breast cancer, the blood test could also be applicable to early-stage cases. He stated, “The liquid biopsy has the potential to make treatment decisions faster, more personalized, and ultimately more effective.”

As clinical trials continue to assess whether adapting treatment based on early ctDNA results enhances patient outcomes, the implications of this research could significantly reshape breast cancer management, offering hope to many facing this challenging diagnosis.