Blood test for colon cancer screening approved by US regulators | Hacker News Reader

Blood test for colon cancer screening approved by US regulators

apnews.com

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This looks like it barely detects pre-cancerous growths, so it's pretty much too late by the time it finds something, as it's already turned into cancer.

What do you mean by "too late"? It's much easier to treat a small tumor than a large one.

How often do you plan on getting the test?

It's already turned into cancer by the time it's detected in most cases with this test, which could be too late. My brother died of colon cancer at 42 because they found a tumor and couldn't operate due to its location.

Colonoscopies, while unpleasant, have come a long way. I get one very 5 years and they have removed pre-cancerous growths.

Blood tests for abnormal circulating cells are a method of future. For example a blood sample test of a pregnant woman can detect many genetic abnormalities and sex of the fetus. It is based on minimal amount of DNA that can be reliably traced. The same can theoretically be done for cancerous cells if their DNA can be distinctly identified.

These are tests of circulating cell-free DNA (cfDNA), not circulating cells. The fraction of circulating _cancer cells_ is too low (outside of blood cancers or metastatic cancers) to be technically feasible to detect; ditto in pregnancy. By contrast, while there isn't much cfDNA (DNA fragments floating around in blood plasma outside of cells) -- on the order of 1-10 ng/mL -- there's enough to extract reliably, and critically, the fraction of that that is tumor-derived (or fetally-derived, for prenatal testing) can be high. It's already high single to low double digit percent at 10-12 weeks of gestation, and can go much higher in some cancers.

But the biggest challenge for these tests is that this "tumor fraction" can be very very low in early stage cancers, which is why stage I sensitivity tends to be quite poor.

There is long time to go until a useful "cancer biomarker", sadly. Cancer is a stubborn problem.

I’m really excited for the possibilities liquid biopsies like this introduce. I look forward to when I can get these in an annual physical without having to pay out of pocket and/or jump through a bunch of hoops

Not to disparage a test of equal veracity, but this test demands a blood sample. The stool test is swipe two sticks through your crap on a flushable paper sheet in a toilet, seal, and post.

The stool test is well understood and ships out worldwide. Maybe there are concerns about preservation of the sample, postal thermal chain issues, but this one, it means a bill. It's probably similar back-end cost but to the patient or health fund, this one costs more.

Why is a blood test which is at best as accurate as a stool test "better" to use?

A blood test seems like it's much more reliable and simpler, because you don't have to rely on the patient to do it. You already need to get a blood sample for your annual health check anyway, so it's pretty easy to just add yet another test to the battery of tests they're doing with that blood draw. Stool and urine samples are just extra work for the patient to do, and to make sure they're done.

Good point. So this test will fold into the standard bloods battery, and it's cost amortizes out against annual tests.

Those are concerns for a doctor and his/her set of patients. For you, if you're willing to do the stool test, then there's no difference. Right?

I don't follow: I am the patient. For me, a blood test is simpler, because there's absolutely nothing for me to do. A stool test requires me to find not one, but two times before I go to the clinic when I need to poop, and to then go through the task of collecting samples from those poops. (The annual stool test requires 2 samples from two separate BMs.) A blood test literally means absolutely no work or extra time, because I'm already getting a blood draw done at the clinic anyway.

It's going to be the same for every patient. The clinic doesn't have to worry about patients forgetting to bring their stool samples, forgetting to do both of them before their appointment, doing them poorly (getting a bad or insufficient sample), etc. The clinic can control everything much better since the blood draw and the handling of the samples is entirely under their control.

Yeah stool tests are annoying, I done mine in clinic, having to hold it day before, going to the clinic restroom, laying out toilet paper etc

Most of your comments were about patients in general." In fact, your last paragraph is entirely about that.

For me (or you) in particular, those concerns are irrelevant. It's just what we prefer. "Everyone" might like Taylor Swift, but if you don't, well... there you go.

You're still not making any sense. You prefer taking a stool sample on your own time to doing literally nothing at all and (as far as we know) getting the same test result? Really?

> You're still not making any sense.

OK, how about this: IF you take a stool sample, the results are just as informative as a blood test. That's what they said. So it's up to the patient.

Obviously not doing anything cannot be better. Your second sentence is the one that makes no sense.

Did you not read the exchange before? Yes, not doing anything at all IS better, because they can get a blood sample from the blood they're ALREADY drawing from you.

So, you have two choices: 1) do a blood draw AND a stool sample, or 2) do a blood draw only.

Which one do you think is less work for the patient and the provider? #2 involves absolutely no extra work for the patient.

Is this really that hard for you to understand?

Maybe you can drop the insults, so we can take you seriously. Or else just go away. Why do you even care?

If you can't understand simple English and basic logic, then I can't help you. There's no insult in my prior message; you just seem to be completely unwilling or unable to understand a simple concept.

I think the main thing that is exciting about this is that it can hopefully be extended to other cancers. Currently, detecting lung cancer involves imaging with radiation that can itself trigger cancer, but imagine a world in which you can get screened for all cancers from a blood test.

It's called a multi-cancer early detection test and they already exist.

There's still value in specific tests, though.

It already has been extended to other cancers. This general type of assay is known as a liquid biopsy. There are a few commercial tests on the market such as Grail Galleri. Accuracy isn't as good as a regular biopsy but accuracy and clinical use will increase over time.

https://my.clevelandclinic.org/health/diagnostics/23992-liqu...

There are many cases where you're getting blood drawn already and if adding another test onto that is inexpensive, that's a pretty convenient add-on. That's useful for many reasons.

I was also wondering how it performed compared to a stool test, so I looked it up, and found "While the blood test caught 83% of the cancers found by colonoscopy, it missed 17%. That’s on par with stool-based tests."

And will combining the two tests catch a higher percentage? Could go as high as catching 97%, although I suspect lower due to some correlation between what cancers the two tests will pick up (eg. not advanced enough to leak blood into stool may equate to not advanced enough to leave markers in blood). But it will also increase chances of a false positive.

Does anyone know the detection rate of this blood test when combined with a FOBT stool test?

“The test missed 17% of cancers, performance that is on par with stool-based tests.”

I took a stool-based test about 6 years ago and passed.

Yesterday I got back from surgery to remove a colon tumor that was discovered about 3 weeks ago. Colon tumors usually take several years to grow.

I recommend making the time to get a colonoscopy because small polyps are removed at that time. Once they grow, it’s surgery then possibly 6 months of chemotherapy. Many colon tumors show no symptoms.

On a side note, my tumor was making me anemic and my Apple Watch was telling me my Cardio Fitness was decreasing, which wasn’t physically noticeable on my walks until recently.

> stool-based test about 6 years ago

Current guidance is to repeat the test every year.

How early can it detect colon cancer? The thing is avoiding surgery requires catching the tumor when it’s a small polyp. You get chemotherapy if your tumor reaches a lymph node.

I think the tests are great but the colonoscopy was a breeze compared to what comes after you find a tumor.

These tests can be taken before colonoscopies are recommended

Also, for some reason colon cancer is increasing in young people so definitely use these tests but still get that colonoscopy when the time comes.

https://www.yalemedicine.org/news/colorectal-cancer-in-young...

Australia offers stool tests (fecal occult blood test) every 2 years starting at 45. The increased frequency may help. But yes, you can't ignore other symptoms and I hadn't realized the false-negative rate was that high. Hope you have seen the last of your cancer!

Here in Japan, stool tests are done every year at that age as part of the required health check.

These wearables have a crazy amount of potential when it comes to health. It's phenomenal you had this extra data point

I wish you clean margins and a speedy recovery.

The Cardio fitness tracking change is interesting. Is that the VO2 max? By how much did it change over what time frame? Had the clinician(s) seen or heard of that before?

Yes, it’s VO2 max. Don’t want to give my numbers but I reached low ability. I’m mainly a walker. The hills started to get difficult. I had a persistent cough that never went away after a winter cold, and shortness of breath. Now think the cough was actually caused by iron deficiency but I’m not a doctor. Went to an ENT, pulmonologist, and GI before we tracked down the issue.

No one bought into the Apple Watch numbers. I researched it on the Internet and no one really knows how it’s calculated. It could have been any number of issues. I’ll add being anemic to the possibilities.

What apple watch do you have? Also wishing you an uneventful and speedy recovery.

The latest model from last fall.

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