A simple blood test can predict how patients will respond to Breast Cancer Treatment before or shortly after therapy begins, enabling doctors to adjust care earlier and potentially improve survival, researchers said.
Scientists at the Institute of Cancer Research in London have developed a liquid biopsy that measures fragments of cancer DNA circulating in the blood, offering an early indicator of whether a specific treatment is likely to work. The findings are based on a study of patients with advanced breast cancer.
Breast cancer is the world’s most commonly diagnosed cancer, affecting more than two million people each year. While treatments have advanced, clinicians often cannot determine in advance which therapy will benefit an individual patient.
Test Uses Cancer DNA in Blood
The new test analyzes circulating tumor DNA, or ctDNA, released into the bloodstream by cancer cells. Researchers measured ctDNA levels in blood samples from 167 patients before treatment began and again four weeks later, after one cycle of therapy.
Patients with lower ctDNA levels at the start of treatment were more likely to respond, the study found. Similar associations were seen in samples taken four weeks later.
“Our study shows that a simple blood test measuring circulating tumor DNA can provide an early prediction of whether a patient’s response to Breast Cancer Treatment will be effective,” said Dr. Iseult Browne, a clinical research fellow at the Institute of Cancer Research and the study’s first author.
Early insight could help doctors avoid ineffective drugs and switch patients to alternatives before the cancer progresses, Browne said.
Results Vary by Cancer Type
Patients were divided into two groups based on cancer type and genetic mutations. One group had cancers with mutations such as ESR1, HER2, AKT1, AKT, or PTEN and received treatments matched to those mutations.
The second group included patients with triple-negative breast cancer, an aggressive form accounting for about 10% to 15% of cases worldwide. They were treated with a combination of the PARP inhibitor olaparib and the ATR inhibitor ceralasertib.
Among patients with triple-negative breast cancer, low ctDNA levels before Breast Cancer Treatment were associated with longer progression-free survival. Their cancer remained controlled for a median of 10.2 months, compared with 4.4 months for those with higher ctDNA levels.
Response rates also differed. About 40% of patients with low ctDNA levels saw their tumors shrink or disappear, compared with 9.7% of those with higher levels.
Early Changes Signal Outcomes
After four weeks of Breast Cancer Treatment, patients in both groups whose ctDNA was no longer detectable experienced significantly better outcomes. In the first group, cancer was controlled for a median of 10.6 months, compared with 3.5 months for patients with detectable ctDNA.
In the triple-negative group, patients with undetectable ctDNA after four weeks saw cancer control last about 12 months, versus 4.3 months for others.
“These findings support the use of ctDNA as a noninvasive biomarker for predicting outcomes and monitoring treatment response,” Browne said.
Prof. Nicholas Turner, a professor of molecular oncology at the institute, said the approach could also apply to earlier-stage disease. “This has the potential to make treatment decisions faster, more personalized, and ultimately more effective,” he said.
