A Blood Test That Screens For Cancer

sciencehabit writes "People usually find out that they have cancer after developing symptoms or through a screening test such as a mammogram—signs that may appear only after the cancer has grown or spread so much that it can't be cured. But what if you could find out from a simple, highly accurate blood test that you had an incipient tumor? By sequencing the abnormal DNA that a tumor releases into a person's bloodstream, researchers are now one step closer to a universal cancer test. Although the technique is now only sensitive enough to detect advanced cancers, that may be a matter of money: As sequencing costs decrease, the developers of the method say the test could eventually pick up early tumors as well."

Comments

Nobel prize

[mmHg760]

If it works with early forms of cancer, this is nobel prize material.

Re:Nobel prize

[paiute]

Hold the phone, there, Alfred. You have to think about how early you want to be able to find mutating cells. There is a sweet spot of detection - when the cancer is not yet so advanced that it can be treated - below which you may want to think twice about going. If this research results in the ability to detect cells as soon as they mutate, you and the media may think this is a great advance, but the body's immune system is able to sense and kill the vast majority of mutating cells before they grow into a tumor. At a certain detection level, the test is going to give positive results for "cancer" for most people. Then what do you do? You go to the doctor and the doctor tells you that you have malignant cells in your body. Are you going to not worry or are you going to demand treatment?

Re:Nobel prize

[bluefoxlucid]

Even better, the false positive rate is important. Regular testing for ovarian cancer in women is something you simply should not do; an ovarian cancer test should only be done if your doctor thinks you have ovarian cancer. Because of the rate of false positives, the rate of false positives in follow-up tests, the rate of complications, and the rate of death in complications, it turns out that roughly 1 in 1000 women who don't get regular testing would die of ovarian cancer, whereas if every woman over age 50 got regular ovarian cancer testing once a year we'd see a death rate of 3 in 1000 due to complications from unnecessary surgery to treat the non-existent cancer in false-positive cases.

If this leads to people looking for cancer that doesn't exist or isn't important, a lot of false positives will start occurring. Even if it's highly accurate at detecting cancer, it won't tell you anything about the cancer. Now you have to look for it. So many cancer tests, so much false positive... you might find several cancers that don't actually exist, because the tests raise false positives occasionally and you're running tests for everything. False positives lead to unnecessary treatment, which is expensive and harmful. You're better off playing cancer roulette.

Re:How much money...?

[gagol]

The researchers should pitch the project to hypochondriac billionaires.

Every cancer is different

[clickclickdrone]

The reason it's so hard to treat and there are so many treatments is that each and every cancer has it's own unique fingerprint in terms of how it works, what it responds to.

It would be nice but I can't see any one test being able to identify all possibilities any time soon. As the article says, it's a step.

Re:Every cancer is different

[MrEricSir]

The methodology seems to account for the many types of cancer, at least in theory, since it's based on finding differences in DNA sequences. As long as a fingerprint exists wouldn't this technique find it?

But this also sounds very preliminary. The sample size was very small and it took a month to get the results.

Re:Every cancer is different

[phayes]

I'm not sure that scanning for genetic changes will turn out to be useful.

Not every genetic change results in cancer as many will result in the cells dying off or being innocuous. Working on bringing the detection threshold down to low enough values to detect small tumours may just end up detecting many small cancers.

In addition, recent work shows that many small cancers are not as problematic as as long been thought. We now know that the body naturally wipes out many cancers without help. Detecting the small cancers that need treatment is much harder than it appears.

Re:Every cancer is different

[clickclickdrone]

may just end up detecting many small cancers

Exactly. ISTR reading that at any one time, most people have dozens of small 'cancers' but in most cases, the body destroys them before they get a hold. It's only when our own defences fail that the cancer goes on to become a 'proper' one and become a health hazard.

Re:Every cancer is different

[kkwst2]

I really think you guys are worried about the wrong end of this. It is highly unlikely that this test is going to be too sensitive any time soon...quite the opposite, the key will be making it sensitive enough to be useful. One or a few cells aren't going to make enough DNA that you would have any reasonable chance of picking it up in a random blood sample. There would have to be some critical mass there already, and who knows, but I would guess that the amount of DNA released into the blood by even an in situ is going to be too small to detect.

It is true that cells mutate fairly frequently, but most of these are not "cancer". Cancer implies that it grows invasively. These sequencing tests would be looking for certain genes known to be linked with cancer. Perhaps over time they will develop heuristics that will allow for detection of mutations not previously characterized but initially it would probably be limited to cancer genes already understood. But my initial concern is whether early cancers dump enough genetic material into the blood for this to be useful for early detection. I'll bet that it is only after it becomes invasive that it releases enough DNA to detect.

It may not help

[sirwired]

Some screening tests for cancer byproducts already exist, like the PSA test for prostate cancer. Other early-detection tests abound, such as Mammograms and Colonoscopies. While some of the screening tests, such as the Pap Smear, have shown to dramatically reduce cancer deaths, others, such as the PSA and Mammogram have detected a lot of cancers, but done absolutely bupkis to reduce death rates when given to populations not otherwise at high risk. Colonoscopies work, but are extremely expensive vs. the benefit they provide. (As in, it'd be a lot more efficient to spend healthcare dollars elsewhere, and there are other screening tests nearly as effective that are much cheaper.) Apparently they don't do a good job detecting aggressive cancers in those populations early enough to make a difference. With how fast some aggressive cancers work, the tests might have to be administered several times a year (at the cost of countless billions) to make any difference.

In addition, the PSA and Mammogram HAVE caused billions to be spent on procedures with quite severe side effects to further diagnose, and treat, problems that almost certainly would not have killed their "victims." Most Prostate tumors grow slowly enough that you could leave it alone for the rest of your life, and die of something else instead; meanwhile, prostate cancer treatment almost always causes problems with incontinence and impotence; two major quality of life issues. Most "breast cancers" detected by mammograms are Ductal Carcinoma In Situ, another type of cancer that is unlikely to kill you any time soon.

We need to think VERY carefully before rolling out any MORE widespread cancer screening tests, since many of the ones we have now simply don't work.

Your headline is too true

[sirwired]

Your headline is more true than you realize... although you don't realize it.

Something like 2/3rds of the population that we would consider to die of "old age" (generally defined as dying of a condition that predominately kills the elderly, and doing so at around, or greater, than the average lifespan for a developed country), have been discovered, upon death, to have cancer of some sort, but cancer that did NOT contribute to their death. IIRC, the most "popular" are Prostate, Breast, and Brain tumors. Some of those tumors may have been decades old, but slow-growing and non-aggressive enough to simply not be an issue.

Not all cancer is worth detecting if it's almost inevitable that you'll die from simply "wearing out" first.

Re:Here's Some Cancer Reality:

[bluefoxlucid]

Yerba mate, green tea, and black tea are all highly anti-cancer. Mate is actually awesome for this; steamed green tea is pretty close; black tea less so, but it has its own strengths over the others. It's worth having a pot of Earl Grey or Irish Breakfast Tea in the morning, and a pot of green tea (gunpowder, any of the various $15-$200 Sencha greens, etc) in the afternoon.

Meanwhile people cry about HFCS, which is an abomination but relatively harmless; look at all the wheat we eat, and our response is to eat whole grains because they're less bad. People figure this out and go Atkins, instead of just eating less than 3000 calories from wheat every day. Over-salted, fumigated crap gets pureed, strained, cooked, then mixed with benzoates and sorbates and parabeens for us to eat or rub onto our skin. All that's bad, but removing it all won't really help if you keep eating crap--like tons of wheat, tons of rice, tons of greasy fatty shit, all things that are good for you but not so god damn much with so little else--and keep sitting on your ass all the time.

Those toxic chemicals will go away if you bike to work every day. Live 5 miles from work? That's 10 miles a day. Suck down potassium and magnesium and sodium out of a CamelBak, chomping on Clif bars if you need it, and shove a greasy full English down your throat in the morning cooked in a ton of lard. Hell, use the canned sorbated bullshit, your body will just shove it out your lymph system while you burn through all that crap.