Cell-free DNA is small fragments of DNA that circulate in the bloodstream and other body fluids. In cancer care, it is commonly measured from a blood sample as part of a “liquid biopsy.” Some of this DNA can come from tumor cells, which may help clinicians learn about a cancer without a surgical biopsy. It is also used in other fields such as prenatal testing and transplant monitoring.

ctDNA stands for *circulating tumor DNA*. It is small fragments of DNA from cancer cells that can be found in blood and sometimes other body fluids. Clinicians use ctDNA testing as a type of “liquid biopsy” to learn about a tumor without taking a tissue sample. It is commonly used in oncology to help guide treatment choices and monitor cancer over time.

Circulating tumor DNA is small fragments of genetic material from cancer cells that can be found in the bloodstream. It is measured using a blood test often described as a “liquid biopsy.” It can help clinicians understand a tumor’s genetic changes without always needing a tissue biopsy. It is commonly used in modern oncology to support diagnosis, treatment selection, and monitoring.

Liquid biopsy is a laboratory test that looks for cancer-related material in body fluids, most often a blood sample. Instead of removing a piece of tumor tissue, it analyzes tumor signals that circulate through the body. It is commonly used in oncology to help guide treatment selection and to monitor disease over time. It may be used alongside imaging and tissue biopsy rather than replacing them.

A Companion diagnostic is a medical test used to help guide the use of a specific cancer treatment. It looks for a biomarker (a measurable feature such as a gene change or protein level) that predicts whether a therapy is more or less likely to help. It is most commonly used in precision oncology, where treatments are matched to tumor biology. It may be performed on tumor tissue, blood, or sometimes other samples, depending on the cancer and test.

A Biomarker is a measurable sign in the body that provides information about a health condition. In oncology, a Biomarker can come from a tumor, blood, or other tissue and help describe cancer behavior. Biomarkers are commonly used in cancer screening, diagnosis, treatment planning, and follow-up. They can guide decisions, but they rarely replace clinical evaluation and pathology.

Measurable residual disease is the small number of cancer cells that can remain after treatment and are too few to see on routine tests. It is measured with sensitive laboratory methods rather than standard microscopy alone. It is most commonly used in blood cancers such as leukemia, lymphoma, and multiple myeloma. In some settings, similar “minimal disease” concepts are being explored in solid tumors using blood-based testing.

MRD stands for **measurable residual disease** (also called **minimal residual disease**). It describes **very small amounts of cancer** that may remain after treatment, even when standard tests look normal. MRD is most commonly discussed in **blood cancers** such as leukemia, lymphoma, and myeloma. It is also being studied and used in selected **solid tumors**, often through blood-based testing.

Minimal residual disease means a very small number of cancer cells that remain after treatment, even when tests show a complete response. It is most commonly discussed in blood cancers such as leukemia, lymphoma, and multiple myeloma. Minimal residual disease is measured using sensitive laboratory methods on blood or bone marrow samples. Clinicians use it to better understand relapse risk and the depth of response to therapy.

Clinical benefit rate is a way to summarize how many people’s cancers improve or stay controlled on a treatment. It usually counts tumor shrinkage and meaningful periods where the cancer does not grow. It is most commonly used as an outcome measure in oncology clinical trials and some research reports.