If you have had cancer or know someone who has, then you are familiar with biopsies.
During a traditional biopsy, your doctor cuts out a tumor or a piece of suspicious tissue from a patient to examine under a microscope, in order to determine whether the cells are cancerous and, if so, what type of cancer they represent. Now, more than ever, the cells are also tested for genetic changes known to be associated with that type of cancer to give us clues as to the most effective treatment.
A liquid biopsy, on the other hand, doesn’t involve cutting out tissue. This non-invasive blood test is performed to look for pieces of DNA from tumor cells that are in the blood, to provide researchers and physicians with information about your cancer.
Liquid biopsies are used in regular clinical practice for patients for whom tissue biopsies are too small to allow genomic analysis and for on-going research.
“We are doing studies to determine if a liquid biopsy can be used to help find cancer at an early stage, to help us plan treatment or to find out how well treatment is working,” says Dr. Raja Mudad, a medical oncologist at Sylvester Comprehensive Cancer Center, part of the University of Miami Health System. “Because we can take multiple samples of blood over time, it should help us keep track of molecular changes taking place in a tumor. In patients with known molecular abnormalities, it may also be useful in assessing response to treatment.”
We hope in the not too distant future that this technique can become the standard of care.
Tumors shed free-floating DNA into the bloodstream as the cells within them die. Collecting and analyzing this DNA allows doctors to determine which therapies have the best chance of working and which are likely to be ineffective. Because this type of biopsy requires only a simple blood draw, samples taken repeatedly over the course of your treatment could track changes in the quantity or composition of tumor DNA and show your doctor how well or poorly a particular therapy is working.
That way you can change to a more effective treatment sooner, and not waste time and energy with a treatment that isn’t working. This approach is currently being investigated.
For example, says Dr. Mudad, all lung cancer patients need an initial tumor surgical biopsy to confirm the diagnosis of cancer. Then, liquid biopsies can detect mutations that can help your doctor select individual therapy, especially if not enough material was available from the tissue biopsy. Patients with lung cancer and certain mutations who receive mutation-specific, also called targeted, therapy may develop a different mutation over time, causing resistance. Liquid biopsy may detect this resistance even before X-rays can see cancer progression.
The future of liquid biopsies
“Liquid biopsy represents a significant advance in the field of oncology,” says Dr. Mudad. “It can help in a variety of cancers, discovering new and treatable targets. And as we discover new abnormalities in cancers, new drugs are developed, which will provide more treatment options for patients.”
Mary Jo Blackwood, RN, MPH, is a contributing writer for the UMiami Health News blog. She is a two-time breast cancer thriver, and a long-time freelance medical writer based in St. Louis, MO and Hartsel, CO. She has written physician-to-physician magazine articles, consumer health articles, and webpages for cancer patients, among other things.