More on screening for colon cancer

In May 2016 we published a News item looking at new DNA-based tests that may be useful in screening for early colon cancer. A recent study from the US shows that there may be potential for detecting very early cancers and even pre-malignant changes in polyps in the bowel that may subsequently turn into bowel cancers.

Currently the most common screening methods in Australia are based on the faecal occult blood test which detects very tiny amounts of blood released into the stool by colon cancers.

This new technique is based on the science of metabolomics. Metabolomics is the systematic study of the unique chemical fingerprints that specific cellular processes leave behind. Because cancers are different from normal tissues it is reasonable to think that they will have some differences in the metabolic processes going on in the cells and that these differences may leave a “signature” in the metabolites or chemicals within cells and tissues and within the blood, urine or faeces.

Scientists at Washington State University and Johns Hopkins Medical School used a technique called ion mobility mass spectrometry coupled with liquid chromatography to screen a vast array of chemicals that are excreted in the stool in normal mice, mice genetically engineered to have pre-cancerous colon polyps and normal and cancerous tissues from mice and humans.

They found that they could detect consistent differences in some of the chemicals excreted in the faeces of the mice with polyps and that they could distinguish them from normal mice. This "metabolic fingerprint" matched changes in both mouse and human colon tumor tissues that they had previously studied.

There is a very long way to go before this test will be proven to be useful in clinical practice. The essential next step is to perform the test using human stool samples to see if a similar fingerprint can be found in people with very early or even pre-malignant changes in their bowel epithelium which is where bowel cancers form. However, if the researchers are successful in making the test work in humans then it would be a major step forward because current faecal occult blood testing is relatively insensitive in detecting polyps and very early stage cancers.

The equipment needed to perform the test is quite sophisticated but related forms of mass spectrometry are becoming common in modern pathology laboratories and are used in the detection of drugs, hormones, metals and even identification of bacteria in the microbiology lab. If the test was proven useful it could be easily adopted and could possibly have the same sensitivity in detecting polyps and cancers as colonoscopy but would save many people having this very effective but invasive and expensive test.

Further Reading
Colon Cancer News Today
Abstract of paper

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