Why does lung cancer so often spread to the brain?

For people living with lung cancer, one of the most serious worries is often the cancer spreading to their brain.

Brain metastases are more common in lung cancer than in almost any other cancer type, and they bring significant neurological symptoms, reduced quality of life, and historically limited treatment options.

A new review published this week in Science Signaling* sets out what scientists now understand about how that spread happens and where new vulnerabilities might be found.

The process unfolds in stages. Cancer cells break away from the original tumour, invade surrounding tissue and enter the bloodstream. The review describes how factors including oxygen levels in the tumour environment and the physical stiffness of surrounding tissue influence which organs those cells are most likely to reach.

Getting into the brain is the next challenge the cancer cells face. The blood-brain barrier is one of the body’s most carefully defended boundaries, designed to keep harmful substances out.

The review explains how cancer cells exploit specific biological pathways to cross it, squeezing through the tight junctions that normally make the barrier so effective.

Once inside, they face a completely different environment from where they started. Surviving and growing there requires significant adaptation. The review looks at how cancer cells interact with the brain’s own resident cells and how the surrounding environment can either support or resist tumour growth.

What makes this research particularly relevant right now is that treatment is beginning to catch up.

At the European Lung Cancer Congress in Copenhagen last month, new data showed that several targeted drugs are demonstrating real activity inside the brain in lung cancer patients with specific mutations. Whether a drug can penetrate the blood-brain barrier is now a central question in how new treatments are designed and tested.

The biology is becoming more understood. The treatments are beginning to follow.

* Source: Chafe SC, Mobilio D, Singh SK et al. Emerging paradigms in the study of brain metastases. Science Signaling. 7 April 2026. doi:10.1126/scisignal.adj9726