Question: My dad’s doctor recommended a liquid biopsy in addition to a tissue biopsy when he was diagnosed because the liquid biopsy would be faster. Why is this important?  

(Answered by Dr. Mohana Roy from the Stanford Department of Medicine during her appearance at the April 16 2024 Lung Cancer Living Room. It has been edited slightly for this use.)

Answer:

Biopsies are an important part of the diagnostic process for lung cancer. A tissue biopsy involves taking a small piece of tissue for examination by a pathologist—but it can take a long time to get results. A liquid biopsy, also known as a blood biopsy, examines a blood sample to detect cancer cells.

While it is not yet standard practice, many doctors are now doing tissue and liquid biopsy testing at the same time. We usually don’t do a blood biopsy if it’s an early-stage disease because we think the blood circulating DNA correlates with the amount of tumor present, but we will use blood biopsies on anyone we think is stage 3C+ (IIIC) and stage 4 (IV).

A tissue biopsy is still gold for us, but a blood biopsy addresses the quality/process issue: We want information sooner. Although data shows that in some cases, starting treatment 2 weeks earlier for metastatic disease does not improve survival, a 2-week wait for the person is still excruciating. Getting blood biopsy results sooner is generally better and allows treatment to start earlier.

Timeliness around biomarker testing are not just about how quickly we can get back the results; it also affects follow-up CT scans. People then wait 2 weeks for the results, leading to “scanxiety,” which is a very real thing and affects mental health. Sooner is better, and while this deduction might not be data-led, it is people-led.

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