CYFRA 21.1 (Cytokeratin-19 fragments)

CYFRA 21.1 measures fragments of a protein called cytokeratin 19, which can be released into the blood when certain cells break down. It is used as a tumour marker, most notably for lung cancer, particularly the type known as non-small cell lung cancer. It is used mainly to help monitor known cancers rather than to detect them in the first place.

What it can help assess

• Monitoring known lung cancer, by tracking how levels change during and after treatment to help assess response and check for recurrence
• Supporting the assessment of certain other cancers, including some cancers of the bladder, head and neck, and other sites, where CYFRA 21.1 may also be raised
• Adding value alongside other markers, when used as part of a wider assessment

An important note on interpretation

CYFRA 21.1 is not a screening or diagnostic test for cancer. Levels can be normal in early disease, so a normal result does not rule cancer out, and it should never be used to detect cancer in someone without a diagnosis. Levels can also be raised by a number of non-cancerous conditions, including benign lung and liver conditions and kidney impairment. For these reasons the result is always interpreted alongside your full clinical picture rather than on its own.

Why it matters

For people diagnosed with lung or other relevant cancers, CYFRA 21.1 can be a useful tool for monitoring the condition over time and assessing response to treatment. Any result should be discussed with your GP or specialist, who can interpret it in the context of your individual situation and advise on the appropriate next steps.