What should you know about NGS liquid biopsy?

An NGS liquid biopsy analyses tumour-related DNA found in a blood sample to look for changes that may guide cancer care. NGS means next-generation sequencing, a laboratory method that checks many genetic changes in one test. It may be considered when a tissue sample is difficult to obtain, when a treatment decision needs updated information, or alongside tissue testing.

A blood draw collects circulating tumour DNA released into the bloodstream. The laboratory compares detected changes with treatments or clinical options that may be relevant to the tumour type. A result can be positive, negative, or inconclusive. A negative result does not always rule out a tumour change because the blood may contain too little tumour DNA. The test also does not replace scans, examination, or every form of tissue analysis.

Your clinician interprets the report with the cancer type, previous treatment, scan findings, and your general health. A detected change is not automatically a diagnosis of a new cancer or proof that a medicine will work.

Ask why the test is being offered and whether tissue testing is also needed. Tell the team about previous biopsies, current medicines, and recent cancer treatment. After the blood draw, ask when the report is expected and who will explain it. Keep a copy of the result and ask which finding, if any, affects the next decision. Learn more about [Circulating Tumour DNA Testing](/technology/circulating-tumour-dna-testing/) and [Biopsy](/treatments/diagnostics-and-staging/biopsy/).

Contact your cancer team promptly if you develop new or worsening symptoms while waiting for results, such as trouble breathing, chest pain, confusion, severe weakness, or bleeding that does not settle. The blood draw itself usually involves brief pressure at the needle site; seek help for persistent bleeding, marked swelling, or signs of infection such as spreading redness and fever.

What decision will this test help us make? Could a tissue sample provide information the blood test may miss? Which result would change my treatment? How will an inconclusive result be followed up? When should I expect the report and who will discuss it with me?