“Gold standard” and “minimally invasive” get ingrained in physicians’ heads early on in medical school, and later become the foundational pillars for patient care. When determining the best cancer treatment, “gold standard” means taking a tissue biopsy from the patient to genetically profile a tumor. Unfortunately, for many patients, this requires a procedure that is usually invasive, oftentimes painful, and may not yield enough tissue to sample.
Enter the liquid biopsy. A liquid biopsy is a commercial blood test that is as effective as a tissue sample at identifying important mutations in patients with non-small cell lung cancers (NSCLC). A study was conducted at 28 centers (academic and community) across the United States that enrolled 282 patients who were diagnosed with late stage NSCLC. Guardant360 (a liquid biopsy test), and the doctor’s choice of a tissue-based test to look for seven genetic markers in the tumors were both utilized. The liquid biopsy test detected mutations at a higher rate than tissue biopsies, did so less invasively, and produced the results in half the time. The liquid biopsy also found markers in a few people whose tissue biopsies were negative, and it found potential targets for drugs in people who did not have enough tissue to test in the traditional invasive way.
Although approximately 30% of lung cancers can be treated with targeted therapies based on genetic testing, a tissue or a liquid biopsy is done in only about 8% of people with NSCLC. The results of this liquid biopsy study should encourage more doctors to test and, as a result, feel more comfortable making decisions about which drugs to use so patients receive the right type of therapy for their tumors.
The minimal invasiveness and ease of the blood-based testing make it possible to also retest patients if their cancer recurs, which in many cases is due to tumors becoming resistant to treatments. Retesting patients can also help doctors identify the new mutations that are driving the cancer, and assist them in prescribing a different, and more effective therapy. While a handful of conservatists may pinpoint technical hurdles that liquid biopsies have yet to overcome, we excitedly foresee liquid biopsies transforming clinical practice in groundbreaking strides by complementing or replacing imaging to monitor treatment response and by detecting disease after surgery with the intent to cure it, not just manage it. And it will be with a calculated cure that strategically matches the right patient to the right treatment faster. Maybe consider the possibility that liquid biopsies could be used to guide cancer treatment decisions and even screen for tumors that are not yet visible on imaging. Imagine that.