Blood Test Predicts Best Breast Cancer Treatment in 4 Weeks

Imagine starting cancer treatment and knowing within four weeks whether it's actually working, not months later when precious time has been lost.

That's now possible thanks to researchers at the Institute of Cancer Research in London. They've developed a blood test that predicts how well breast cancer patients will respond to specific treatments, even before therapy begins.

The test analyzes tiny fragments of tumor DNA circulating in patients' blood. By measuring these microscopic cancer traces, doctors can now tell which patients are likely to respond to a treatment and which ones need different options immediately.

Researchers tested 167 people with advanced breast cancer, taking blood samples before treatment and again after just four weeks. The results were striking. Patients with low tumor DNA levels before treatment kept their cancer at bay for 10.2 months, compared to just 4.4 months for those with higher levels.

After four weeks of treatment, the predictions became even clearer. Patients whose tumor DNA had become undetectable stayed cancer-free for up to 12 months, while those with detectable levels saw progression in just 4.3 months.

Dr. Iseult Browne, who led the study, explains the game-changing impact. "Knowing this at the earliest stage means we can avoid giving patients drugs that won't work and provide them with alternatives before their cancer has a chance to grow," she said.

The current approach often means waiting months to see if a treatment is working through imaging scans and physical symptoms. This new test cuts that uncertainty down to weeks, sparing patients from ineffective treatments and their side effects.

The Ripple Effect

This breakthrough extends far beyond the 167 patients in the trial. Breast cancer is the world's most prevalent cancer, affecting over 2 million people annually. For years, oncologists have struggled with a frustrating reality: treatments that work brilliantly for some patients fail completely in others.

Now doctors can personalize cancer care with unprecedented speed. Patients who aren't responding can quickly switch to alternative therapies, combination treatments, or enroll in clinical trials for novel drugs. Every week matters when fighting cancer.

Professor Nicholas Turner, who worked on the research, notes the test could eventually work for early-stage breast cancers too. That means catching problems even sooner, when treatments have the highest success rates.

The test offers something beyond medical data: it gives patients answers when uncertainty feels unbearable, helping them and their families make informed decisions about their care with confidence instead of hope alone.