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Promising Blood Test for Cancer of Unknown Primary

blood test for cancer

Cancer treatments work best when you know what kind of cancer you are dealing with. For some, it is unclear where the cancer started so it is more difficult to cure. A new blood test may help with that.


Cancer starts when cells in the body rapidly grow out of control. Most of the time, doctors can find the primary site of the cancer using tests such as CT scans and PET scans. However, there are some cases where the original cancer site cannot be found.

Cancer of unknown primary, or CUP, is diagnosed in about 33,770 people each year in the United States – or about 2% of all cancers. Doctors can biopsy metastatic sites to find out more about the cancer, but knowing the primary site of the cancer helps to formulate a targeted plan for treatment.

Researchers with the University of California San Diego have developed a new blood test that may help determine where in the body a cancer tumor is growing.

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Current cancer blood tests work by screening for DNA released by dying tumor cells. The new test screens for a particular DNA signature called CpG methylation haplotypes. Each tissue in the body has a unique signature as it relates to these. The UCSD team then put together a database of cancer-specific genetic markers as it relates to tissues in 10 locations – the liver, intestine, colon, brain, lung, kidney, pancreas, spleen, stomach and blood.

The test is very much in its earliest stages. Kun Zhang, a bioengineering professor and senior author of the study, calls it “proof of concept.” However, it is a promising step not only to find elusive cancer sites, but may also help in the future reduce the number of invasive surgical procedures such as biopsies.

Journal Reference:
Shicheng Guo, Dinh Diep, Nongluk Plongthongkum, Ho-Lim Fung, Kang Zhang, Kun Zhang. Identification of methylation haplotype blocks aids in deconvolution of heterogeneous tissue samples and tumor tissue-of-origin mapping from plasma DNA. Nature Genetics, 2017; DOI: 10.1038/ng.3805

Additional Resource:
American Cancer Society

Photo Credit:
By AfroBrazilian (Own work) via Wikimedia Commons