New Paper-Based Urine Tests Could Detect Cancer and Heart Disease

Illustration for article titled New Paper-Based Urine Tests Could Detect Cancer and Heart Disease

Diagnosing cancer and heart disease generally requires extensively trained personnel and expensive instruments. But one MIT research group that wants to solve that problem has designed a single injection and paper-based detection system they're hoping to ship them everywhere a letter can travel.

Sangee Bhatia's team developed a molecular detection system that brings a bunch of existing technologies together in a new way to perform this test. Once approved for use in humans, it'll work like this: First you'll get an injection of a nanoparticle solution that can bond to the proteins generated by cancer or heart disease. Next, you'll pee onto the test paper, and if a nanoparticle that's bonded with the disease specific proteins comes out, it'll hit the paper and change colors. So far, in Bhatia's animal studies, this paper-based detection system successfully detected colon tumors and blood clotting, and the hope is that it can be expanded to detect more diseases.

Bhatia sees a variety of markets for this technology. Ultimately she hopes it will help diagnose cancer in the third world, or anywhere where equipment and professionals are hard to come by, but she also sees the potential for it as a home diagnostic or in a clinic setting. But for the time being, if you're concerned about testicular cancers, a pregnancy test is still your best DIY bet. [PNAS via MedicalXpress]

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DISCUSSION

I am a layman. I am not a medical professional. Just getting that right out there. But based on my understanding of early detection, this sounds simultaneously promising and concerning.

The benefit of early detection (again, as I understand it) is that if you can detect an aggressive, fast-moving cancer, that early detection should increase the chances of extending your life. But the concern with early detection is that our ability to detect anomalies that may or may not present in a clinical fashion (i.e. cause any ill effects or speed up mortality) during the person's lifespan. In these cases, the cure may well be worse than the disease.

Couple of interesting articles from David Gorski over at Science-Based Medicine about early detection of cancer that are well worth a read. As expected, the issue is extremely complex.

There are issues of lead-time bias - e.g. two individuals are diagnosed with cancer - the first, through a screening, at 45 - and the second, through clinical presentation, at 50. They both die at 60. In the first case, the survival duration is 15 years, in the second, the survival duration is 10 years - and yet, both died at the same age.


There's also a much more complex issue called "length bias", which has to do with the relative length of the preclinical phase of a particular type of cancer to the clinical phase:
"The probability of detecting a cancer before it becomes clinically detectable is directly proportional to the length of its preclinical phase, which is inversely proportional to its rate of progression. In other words, slower-progressing tumors have a longer preclinical phase and a better chance of being detected by a screening test before reaching clinical detectability, leading to the disproportionate identification of slowly progressing tumors by screening with newer, more sensitive tests."
As well as issues surrounding the detection of microtumors:
"Now, imagine if you will, that a test was invented that was 100% sensitive and specific for detecting prostate cancer cells and that, moreover, it could detect microscopic foci of prostate cancer less than 1 mm in diameter. Now imagine applying this test to every 60 year old man. Somewhere around 40% of them will register a positive result, even though only around only 1/40 of those apparent positives would actually have disease that needs any treatment. Yet, they would all get biopsies. Many of them would get radiation and/or surgery simply because we can’t take the chance, or because, in our medical legal climate, watchful waiting and observation to see if it is going to grow at a rate that would make it clinically apparent in the case of potential cancer are a very hard sell, even when they’re the correct approach."
It's fascinating stuff - and I am not saying that this test is a bad thing (I'm not remotely qualified to make such a statement) - just curious how this sort of urine test for cancer markers fits into the discussion.

Articles:
Early Detection: Part 1
Early Detection: Part 2 (focuses on breast cancer and MRIs)

Also, a followup from last year titled "Redefining Cancer", which addresses the issue with some newer data (the two articles above are from 2008).