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Cell free DNA

Cell-free DNA (or cfDNA) refers to all non-encapsulated DNA in the blood stream.

cfDNA comprises DNA fragments that are physiologically released from apoptotic or necrotic cells into the circulation.

These fragments are rapidly cleared from the circulation by nucleases, renal excretion, and uptake by the liver and spleen.

Higher levels of cfDNA  may be observed in patients with cancer and non-malignant condition such as infection or inflammation.

cfDNA originates primarily from circulating cells, ertain cfDNA molecules arise from deep tissues and can be found in plasma.

cfDNA are nucleic acid fragments that enter the bloodstream during apoptosis or necrosis.

A portion of cell-free DNA can originate from a tumor cell and is called circulating tumor DNA (or ctDNA).

Normally, such fragments are cleaned up by macrophages.

 

Circulating tumor DNA (ctDNA) status adds to the performance traditional risk factors, including the pathological stage, in stratifying patient’s risk for recurrence and need for adjuvant therapy.

ctDNA fragments carry all types of genetic aberrations, single nucleotide variants, insertion/deletions, translocations from the cell of origin and those constitute a highly specific marker of cancer.

The overproduction of cells in cancer leaves more of the cfDNA behind.

These fragments average around 170 bases in length, have a half-life of about two hours.

These cfDNA fragments are present in both early and late stage disease in many common tumors.

cfDNA concentration varies greatly, occurring at between 1 and 100,000 fragments per millilitres of plasma.

The detection of circulating tumor DNA (ctDNA) could give patients who have been treated for their early breast cancer (BC) warning of any recurrence many months before it could be detected clinically or symptomatically (Dicosmo).

Circulating tumor DNA is able to identify a patient who is going to relapse at the locoregional level.

Circulating tumor cells (CTCs) and ctDNA could potentially identify patients who could be spared further chemotherapy.

 

Circulating tumor DNA positivity preceded radiological or clinical evidence of recurrence in Colorectal camncer patients by a median of three months ( Wang Y).

 FDNA is present in the plasma of individuals with breast cancer and can be used to detect patients pre-treatment with localized disease and has a sensitivity at 80% and 97% specificity.

With neoadjuvant chemo therapy breast  cfDNA  levels decreased dramatically and persistence at the end of chemotherapy reflects the existence of residual disease, making it a powerful marker for the detection and monitoring of breast cancer.

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