Slashdot Mirror
UK Team Claims Breakthrough In Universal Cancer Test
An anonymous reader writes UK researchers say they've devised a simple blood test that can be used to diagnose whether people have cancer or not. The Lymphocyte Genome Sensitivity (LGS) test looks at white blood cells and measures the damage caused to their DNA when subjected to different intensities of ultraviolet light (UVA), which is known to damage DNA. The results of the empirical study show a distinction between the damage to the white blood cells from patients with cancer, with pre-cancerous conditions and from healthy patients. "Whilst the numbers of people we tested are, in epidemiological terms, quite small (208), in molecular epidemiological terms, the results are powerful," said the team's lead researcher. "We've identified significant differences between the healthy volunteers, suspected cancer patients and confirmed cancer patients of mixed ages at a statistically significant level .... This means that the possibility of these results happening by chance is 1 in 1000." The research is published online in the FASEB Journal, the U.S. Journal of the Federation of American Societies for Experimental Biology.
This could be a giant step forward in cancer diagnostics, but media reports are - of course - sensationalizing beyond evidence.
In the study, the types of tumors tested share some similarities that might mean findings true of them would not be true of "all cancers". Specifically, none of the lesions tested were tumors of mesenchymal origin. No sarcomas, no fibromas, no leukemias. That's a broad range to not examine, and it means that generalizing this as a test for "all cancers" is premature. Additionally, none of the tumors tested were types that tend to show up in places that lymphocytes have trouble getting to (like the brain, eye, and portions of the reproductive tract).
It is good that they tested against COPD (a chronic inflammatory condition), but it does not appear as if they could distinguish between less-aggressive tumors and inflammatory conditions (I can't tell for sure because of the paywall). It may be that this is a test that is a good indicator of chronic inflammation (seen in many cancers as well as other conditions) rather than a cancer-specific test.
Regardless of the limitations of the preliminary sample set, the findings are very exciting and a potentially amazing discovery in cancer medicine. Kudos to the hardworking scientists involved!
Here is the abstract. The actual paper is behind a paywall.
"ROC analysis of [the test statistic], for cancers plus precancerous/suspect conditions vs. controls, cancer vs. precancerous/suspect conditions plus controls, and cancer vs. controls, gave areas under the curve of 0.87, 0.89, and 0.93, respectively (P<0.001). Optimization allowed test sensitivity or specificity to approach 100% with acceptable complementary measures."
The ROC curve has area under it of 1 for a perfect classifier and 0.5 for wild guessing. This is a more useful measurement than the p-value. (E.g. if I look at height vs sex for humans, it won't take too big a sample to get a great p-value for there being a difference, yet classifying people as male/female depending on whether they exceed some height threshold is a very poor diagnostic system.) I don't have much of a feel for how good ROC area of about 0.9 is for a medical test. I'd guess it is good enough to be useful, but you'd not want to rely on that test alone.
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