Could a Blood Test, Breath Sample or Even Tears Help Detect Breast Cancer?

What if breast cancer could be detected through a blood test, a breath sample or even a few tears?
Researchers are exploring all three, including here in Canada. For women with dense breasts, whose cancers can be hidden on mammograms, this research is particularly interesting.

BREATH: Could a breath test detect breast cancer?
On October 7, IWK Health in Halifax announced it had joined a Canadian study investigating whether breast cancer can be detected through a breath test. The technology, developed by New Brunswick company Breathe BioMedical, looks for chemicals called volatile organic compounds (VOCs) in the breath. Cancer can change the body’s metabolism, potentially producing a pattern of chemicals that can be identified in exhaled breath.

The study is underway in New Brunswick, with IWK now joining as the second Canadian site. Researchers will compare breath samples from women with and without breast cancer to assess the test’s accuracy.
The hope is that breath testing could eventually complement mammography, particularly for women with dense breasts.

Imagine having a mammogram and providing a breath sample that could help identify a cancer hidden by dense tissue.

BLOOD: Could a blood test detect breast cancer?
Researchers in Canada and the United States are investigating blood tests that look for biological changes associated with breast cancer.

In Canada, Calgary-based Syantra has developed an investigational blood test that examines RNA signals in the blood. Changes in certain RNA patterns may indicate that cancer is present. In August 2026, the company reported on a study modelling the potential benefits of adding its blood test to mammography. The findings suggested it could improve early detection if the test performs as expected in clinical practice. That still needs to be demonstrated.

In the United States, Astrin Biosciences has developed a blood test called Certitude, which became commercially available in September 2026.Certitude analyzes thousands of proteins in the blood, using artificial intelligence to identify patterns associated with breast cancer. It is intended to complement mammography, particularly for women with dense breasts or inconclusive imaging results.
In research involving more than 1,200 stored blood samples from women with breast cancer and healthy controls, Certitude detected approximately 93% of cancers. However, its performance in routine screening has not yet been established. The test has not received FDA clearance or approval.

One of the biggest challenges is detecting cancers when they are very small, before symptoms develop. A test that performs well in women already diagnosed with breast cancer may not perform as well when used to screen women without symptoms.

TEARS: Could breast cancer be detected in tears?
Tears contain proteins and other substances that may provide clues about changes happening in the body, including those associated with breast cancer.

An American company, Namida Lab, has developed Auria, a tear-based breast health assessment that is already being marketed in the United States and is available online for delivery across Canada.

Women collect a tear sample at home using a special strip and send it to a laboratory for analysis. The test measures two proteins, S100A8 and S100A9, that may be associated with breast abnormalities.
The company reports approximately 92% sensitivity, but specificity is 58%, meaning false-positive results are a significant concern. Auria cannot diagnose breast cancer or replace mammography, and more independent research is needed to establish its usefulness in routine screening.

Researchers are also exploring other approaches. In 2025, a study described a small device that could detect breast cancer-associated particles called exosomes using just 14 microlitres of tears. The analysis took about 10 minutes. The early results were encouraging, but the study was small and requires validation in much larger groups of women.

What could this mean for women with dense breasts?
Mammography can miss cancers hidden by dense breast tissue. Blood, breath and tear tests work differently. Rather than relying on images, they look for biological signals that may indicate cancer.
Because they don’t depend on seeing a tumour through dense tissue, they could potentially help detect cancers that mammography misses.

Researchers still need to determine how reliably these tests detect early-stage cancers, how many false alarms they produce and whether they improve detection when used alongside mammography.

Even if these tests become part of screening, imaging and, when indicated, a biopsy would still be needed to locate and confirm a cancer.

Where do we go from here?
The possibility of detecting breast cancer through something as simple as a breath sample, blood draw or tears could change how we screen for breast cancer in the future.

Perhaps one day, these tests could help find breast cancers that mammograms miss. Until then, women need access to the screening available today that can find breast cancer early, including additional screening when appropriate for their breast density and individual risk.