12 ms·
Trial of a blood test that detects eight common forms of cancer
- tempestn 9y agoThis was the most exciting part for me: It was trialled on 1,005 patients with cancers in the ovary, liver, stomach, pancreas, oesophagus, colon, lung or breast that had not yet spread to other tissues. Overall, the test found 70% of the cancers. I expected it to be blood cancers only, but this list covers many of the most common forms of cancer. Could be a huge development.
- AstralStorm 9y agoThey glossed over the false positive rate...
- black_puppydog 9y agoWell, in a study that only tests on cancer patients, there are no negative examples to wrongly be classified as positive. That's for the second study (mentioned in the article) to show. Still, this would be great, probably combined with (nearly) equally simple follow-up tests.
- pgt 9y agoFalse positive rate seems pretty key, or the test could be testing for brunettes where 70% of the population is brunette.
- jlebrech 9y agothey can falsely diagnose the wrong type of cancer?
- beberlei 9y agoThis test is probably not being used for "what kind of cancer" but as a cheap and easy way for yearly/bi-yearly tests of the general population as part of prevention.
- dx034 9y agoWith a 1% false positive rate that won't work I guess. False positive rate needs to be much smaller.
- justinpombrio 9y agoI don't think they do. If someone tests positive, I imagine the next step would be to do more thorough (and expensive, and time-consuming) tests and find out for sure.
- Bron101 9y agoFrom other sources (https://www.medscape.com/viewarticle/891491 https://www.medscape.com/viewarticle/891491) I was able to find they had a specificity of >99%, with a sensitivity averaging 70% but was as low as 20% on certain cancers (esophageal cancer). With such an excellent specificity this sounds promising as a cheap screening tool, although the sensitivity is too low in some cancer types to be used as a means to rule out cancer.
- tischler 9y agoAs a reminder: true positive rate (TPR, a.k.a. hit rate, recall, specificity) TPR = TP / P = TP / (TP + FN) specificity (SPC) or true negative rate SPC = TN / N = TN / (TN + FP)
- kmmlng 9y agoYou labelled both TPR and TNR as "specificity". True positive rate should be sensitivity.
- tischler 9y agoOops, thanks. I've always had struggle remembering these terms because they are so confusing. "Specific" means that something only relates to one particular element X in a set of more than one thing. Given that meaning, one would expect specificity to mean "how good is the test at correctly reporting the thing it is designed to report X rather than confusing a different thing (an element from the complement of X) for X", but that is sensitivity. Instead, specificity means that with respect to the complement: "how good is the test at correctly reporting all the other elements in the set ¬X as negative rather than confusing an element from ¬X for X". "Sensitive" has a clearer intuition: For example when you want to detect a weak signal, then if your antenna is more sensitive, you can better pick up the signal, thus you are better at telling whether the signal is really there (you have a better true positive rate). I cannot think of a better name for TNR, though, other than simply sticking with TNR and TPR.
- 9y ago
- HyperMassive 9y agoOn national news they mentioned 1% came back positive for people who were believed to be entirely healthy. Unfortunately it was anonymous so they could not get back in touch with the false positive patients. The spokesperson made it very clear its early days and they are looking to refine it further; they anticipate it to be a cheap and accessible 'first-call' test in regular cancer screening, not a definitive diagnosis.
- carlmr 9y agoAccording to https://www.cancer.org/cancer/cancer-basics/cancer-prevalence.html https://www.cancer.org/cancer/cancer-basics/cancer-prevalenc... about 15 million Americans have cancer. That is about 5% of the population. Given those numbers and assuming you have a positive result for a random person, that means according to Bayes: C being cancer, H healthy, P positive test P(C|P) = [P(P|C) * P(C)] / [P(P|C) * P(C) + P(P|H) * P(H)] = [ 0.7 * 0.05] / [ 0.7 * 0.05 + 0.01 * 0.95] = 0.035 / (0.035 + 0.0095) = 0.7865 That's pretty good. If you have a positive test result, in 4 out of 5 cases it actually is cancer. It gets a bit worse if you account for the fact that this test only works for a subset of the cancers. But this would be useful as a pre-screening.
- nonbel 9y agoSince this is a screening test, I don't think that 15 million number is correct for prevalence. You are using % of population diagnosed with cancer. The correct value would be the % of population with undiagnosed cancer.
- carlmr 9y agoTrue. That is really difficult to obtain though. But assuming that most people are eventually diagnosed with cancer (even if just close to death), then a similar maybe a little lower population must have undiagnosed cancers. In the end you'll need a properly conducted study with random undiagnosed people to get reliable numbers though.
- 9y ago
- phaemon 9y agoThey did not gloss over it. It's right there in the abstract: http://science.sciencemag.org/content/early/2018/01/17/science.aar3247 http://science.sciencemag.org/content/early/2018/01/17/scien... Please realise that, just because a detail is omitted in a news report, it does not mean that the team who did the research didn't think of it, or tried to hide it. This is just the usual shoddy reporting by the BBC.
- huhtenberg 9y agoLooks paywalled.
- haraball 9y ago> The specificity of CancerSEEK was > 99%: only 7 of 812 healthy controls scored positive.
- dekhn 9y agoa 1% false positive rate. ouch.
- dx034 9y agoIf the blood test becomes widespread you could end up with more false positives than true positives. So probably not useful as a routine test with this error rate.
- ZeroGravitas 9y agoWorth noting that because of anonymity, they couldn't go back and check if those 7 people actually had cancer and just didn't know it. Recently the woman who could smell Parkinson's Disease got one test wrong but when they rechecked they found that she was right, it was just undiagnosed in that person.
- jonlucc 9y ago> because of anonymity, they couldn't go back Is this so? I thought the original researchers would be able to follow-up if they had accounted for it in their consent forms. In other words, they surely have identifying patient information, and even though an outside team couldn't screen the same cohort, that original team could find those 7 patients and ask again in 2 years.
- JohnJamesRambo 9y agoI would be fine with a pretty high false positive rate when you are getting such vital and useful information.
- tialaramex 9y agoWhat exactly are you going to do with this "vital and useful information" keeping in mind that it might also be wrong?
- rocqua 9y agoGet CAT scans. It should be noted that at the moment, the researchers are still working on determining which of the 8 cancers is present in the case of a positive result.
- vidarh 9y agoCAT scans are insufficient to determine if a growth is malignant in many cases. Which would lead you down the road to biopsies, which are also insufficient in many cases. Which would lead to unnecessary radiotherapy, chemo or operations in at least some cases.
- wiz21c 9y agoAre they insufficient because of the way they work, or because their current resolution is too low ?
- cfmcdonald 9y agoCAT scans by themselves are also a pretty major radiation dose which slightly increases your risk for cancer.
- rocqua 9y agoIf there is no way to determine whether a growth is malignant, we are fucked any way. Certainly, this is not the point of a screening test. Screening tests are about cheaply directing further testing.
- rocqua 9y agoA false positive rate of 0.8 .
- lr4444lr 9y agoBut isn't the main point that it motivates people to get tested further, and sooner, when outcomes can be better? It's a sky high false negative rate that would really take the wind out of the sails for me about this.
- cratermoon 9y agoOutcomes are not necessarily better overall for earlier detection, though. For some kinds of cancer, pancreatic, for example, yes. Others, likes prostate or thyroid, not so much.
- cratermoon 9y agoThank you! http://www.latimes.com/opinion/op-ed/la-oe-welch-cancer-treatement-20151119-story.html http://www.latimes.com/opinion/op-ed/la-oe-welch-cancer-trea...
- deleted 9y ago[deleted]
- lawlessone 9y agoIs there a way the general public can help this research or speed it up?
- crb002 9y agoMost basic research is there. It is more of an engineering effort to get full spectrum mRNA and protein histograms cheap and fast enough.
- jamra 9y agoOne of the things I am hoping for is a general database of cancers and the mutations they exhibit. By putting them in a database, we may be able to treat based off the mutation instead of the locality in the body. When my mother was diagnosed with ovarian cancer, she was given chemo therapy for ovarian cancer that was unrelated to hers in everything but location. Since her cancer was very rare, there was no real study that could have helped. If we start keeping a database, it may help us find new treatments and stop giving dying people ineffective poisons.
- xyhopguy 9y agoThose already exist! TCGA for starters..
- nonbel 9y agoInteresting, even the highlighted research on that page is about copy number rather than point mutations, indels, etc, being important: https://cancergenome.nih.gov/newsevents/newsannouncements/sarcoma_2017 https://cancergenome.nih.gov/newsevents/newsannouncements/sa...
- dekhn 9y agoturns out, genomicists have very little idea how the real world works, and they're still arguing over these kinds of things, rather than working out the underlying mechanistic details.
- xyhopguy 9y agoMy (weak) understanding is that the functional impact of a mutation is more important than the type of variations. Otherwise we would see recurrent point mutations rather than hotspots right? FWIW though, people have already been able to predict treatment outcome from mutation profile. Turns out the hard part is picking up on mutations present in only a tiny subset of the tumor.
- sungam 9y ago
- bitwize 9y agoThis is next-level badass and here's why: Not only can we detect cancers earlier and prevent them from getting worse, but if we can detect cancer cells in the blood, we're that much closer to killing them in the blood, preventing or mitigating metastasis and improving the treatment prospects for even later stage cancers. Go science!
- dekhn 9y agothis is a bit optimistic; be aware that press-release-by-science almost always states near-term impact.
- bitwize 9y agoWhile it's too early to tell, what I'm suggesting is not that much of a stretch; currently we treat metastasis by dosing the patient up with chemo and hoping that the dose is enough to effectively wipe out the bloodborne cancer without killing the rest of the patient. Emphasis on hoping; the trickiest bit was always detecting small amounts of cancer cells in the blood. At a very minimum, it will mean more effective and knowledgeable deployment of chemotherapy, but it's not fanciful to imagine that more easily detectable cells are more easily targetable cells.
- dekhn 9y agoI would strongly suggest you spend a decade in the cancer business before making claims like this.
- cratermoon 9y agoExcept that no, earlier detection does not necessarily mean better outcomes. http://www.latimes.com/opinion/op-ed/la-oe-welch-cancer-treatement-20151119-story.html http://www.latimes.com/opinion/op-ed/la-oe-welch-cancer-trea... Dr. Welch is the go-to expert on the problems created by medicine's efforts to detect disease early
- crb002 9y agoThe holy grail is a full spectrum metabolome screen that gets a histogram of both proteins and mRNA. I expect this in the next five years commercially. It will wipe out almost all other tests, be available at your pharmacist.
- ipunchghosts 9y agoWhat companies are working on this?
- sjg007 9y agoNobody, it sounds too good to be true.
- lcfcjs2 9y agoIn the US, this blood test is expected to cost $83,000.