A Caris Liquid Biopsy is a blood test used in cancer care, providing a minimally invasive option for molecular analysis. It is designed for patients with diagnosed solid malignant tumors, particularly when obtaining a tissue sample is not feasible. This test analyzes a patient’s blood to find genetic information from a tumor, giving oncologists detailed molecular insights to guide and personalize treatment decisions.
The Science Behind the Test
The science behind the Caris Liquid Biopsy is the analysis of genetic material that tumors release into the bloodstream. Cancer cells shed small fragments of their DNA and RNA, known as circulating tumor DNA (ctDNA) and cell-free RNA (cfRNA). The test begins with a standard blood draw, and the sample containing these cancer-derived biomarkers is sent to a specialized laboratory for analysis.
In the laboratory, the test employs a technology called circulating Nucleic Acid Sequencing (cNAS). This method sequences cell-free DNA and RNA from the blood plasma and also the DNA and RNA from the patient’s white blood cells. This dual analysis allows scientists to distinguish between genetic alterations from the tumor (somatic mutations) and those that are inherited or related to blood cell production (germline or clonal hematopoiesis variants).
The sequencing process utilizes whole-exome and whole-transcriptome sequencing to scan for alterations across as many as 22,000 genes. This creates a detailed map of the cancer’s genetic landscape from the blood sample. The technology is sensitive enough to detect mutations at a very low frequency, providing a clear picture of the cancer’s drivers.
Clinical Applications and Purpose
An oncologist may order a Caris Liquid Biopsy in several clinical situations. The test provides a non-invasive method to obtain a molecular profile to guide the selection of targeted therapies. Primary uses include:
- Initial treatment planning when a traditional tissue biopsy is not feasible or is considered too risky for the patient.
- Monitoring treatment effectiveness by taking blood samples over time to measure changes in cancer biomarkers. A decrease can indicate a therapy is working, while an increase might suggest the treatment is not having the desired effect.
- Detecting cancer recurrence, as the reappearance of tumor-specific genetic material in the blood can be an early signal that the cancer is returning, sometimes earlier than standard imaging.
- Understanding treatment resistance when a patient’s cancer stops responding to a therapy. The test can identify new genetic mutations that have developed, providing information to select a subsequent treatment.
Information Provided by the Caris Report
The Caris Liquid Biopsy report provides a molecular profile that lists the specific genetic alterations detected in the blood sample. The results are organized to clearly distinguish between tumor-derived variants and incidental findings like inherited mutations or those related to blood stem cells.
The report identifies actionable biomarkers, which are specific genetic mutations, amplifications, or signatures for which targeted treatments exist. It also details genomic signatures like microsatellite instability (MSI) and blood tumor mutational burden (bTMB), which help predict response to certain immunotherapies. This allows the physician to consider more precise treatment avenues.
Based on the molecular profile, the report connects the identified biomarkers to a list of potential treatments. This includes FDA-approved targeted therapies, immunotherapies, and chemotherapy agents that have shown efficacy in cancers with the patient’s specific genetic profile. This information helps facilitate therapeutic decision-making.
The report also serves as a tool for clinical trial matching. Based on the cancer’s molecular signature, it identifies relevant clinical trials for which the patient may be eligible. This can open up access to investigational drugs and novel treatment strategies. Important findings are highlighted to assist the physician in creating a personalized treatment strategy.
Comparison to Traditional Tissue Biopsy
A primary difference between a liquid biopsy and a traditional tissue biopsy is the level of invasiveness. A tissue biopsy is an invasive procedure that involves surgically removing a piece of the tumor or using a needle to extract a sample, which carries risks like pain, bleeding, and infection. In contrast, a liquid biopsy requires only a simple blood draw.
The scope of information provided by each test also varies. A tissue biopsy analyzes a sample from a single tumor site, while a liquid biopsy analyzes ctDNA from the entire bloodstream. This allows the liquid biopsy to capture a more global snapshot of the cancer by detecting genetic material from multiple tumor sites, providing insight into tumor heterogeneity.
These tests are not mutually exclusive and can serve complementary roles. A tissue biopsy is often the standard for initial diagnosis and profiling. A liquid biopsy can then be used for ongoing monitoring, tracking resistance, or detecting recurrence without repeated invasive procedures. The decision to use one or both tests depends on the clinical context, such as the cancer type, stage, and the patient’s health.