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Re-evaluating the Benefits of Cancer Screening
uncleO writes "An article in the NY Times describes two studies that weigh the harm caused by cancer screenings against the benefits they provide. From the article, 'Two recent clinical trials of prostate cancer screening cast doubt on whether many lives — or any — are saved. And it said that screening often leads to what can be disabling treatments for men whose cancer otherwise would never have harmed them. A new analysis of mammography concluded that while mammograms find cancer in 138,000 women each year, as many as 120,000 to 134,000 of those women either have cancers that are already lethal or have cancers that grow so slowly they do not need to be treated. ... In recent years, researchers have found that many, if not most, cancers are indolent. They grow very slowly or stop growing altogether. Some even regress and do not need to be treated — they are harmless."
And the UK is now reviewing the entire breast screening programme it runs to see whether the evidence continues to show that, on balance, good outweighs harm. Tough decisions for all concerned, and an excellent demonstration of just why science is hard to do right.
Among the options:
1) Continue as-is
2) Use more selective screening with (hopefully) greater specificity -- eg familial history, gene markers, etc
3) Stop screening
I'm curious why blood tests aren't peformed regularly. You can certainly request Alpha-fetoprotein (AFP) any time you like, but it is not commonly recommended on a regular basis. AFP can indicate tumors growing in the body. Very high levels of AFP can indicate advanced cancer. In the case of a co-worker who was found to have advanced cancer, on first diagnosis, why not have this marker checked every 6 months?
I've been told a normal reading is about 100-120. Values over 10,000 should be investigated. Lance Armstrong, had levels of over 100,000 when he was diagnosed, with tumors spread throughout his body.
It seems a low impact test, why is it not advised as part of a standard checkup? We'll look for chelesterol, why not Alpha-fetoprotein?
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Seems like someone is driving a huge PR campaign for "let's not have people visit doctors and get cancer screening". It's likely actually just costing a group of HMO insurers more money to have lots of people treat cancers early and undergo lengthy treatment, and then survive, rather than have a smaller number of people detect it too late, do a short treatment, and then just die.
After all, health services are a business. We understand. You can't just have insured people liviing a long time and making businesses lose money.
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I thought that was insolent.
OK, here are the things that can happen in a cancer screening:
1. You find a cancer that will eventually kill you AND that particular cancer has a treatment that works better when started earlier. (True Positive result)
2. You don't find a cancer that you don't have. (True Negative result)
3. You find a cancer or something that looks like a cancer however it will grow so slowly or regress so it won't cause any harm, but then you don't really know which is which so you elect to be treated for same with some morbidity or mortality. (False Positive result)
4. You don't find the cancer that existed and goes off to knock you off just before you design the next iPad killer. (False negative result).
Only #1 and #2 are unequivocally good. #3 might be a bit of a problem - say a lumpectomy for Ductal carcinoma in situ (DCIS) - which is painful and maybe slightly disfiguring but doesn't really change your overall health or it might be a radical prostatectomy for an indolent prostate cancer that would never kill you but now your are incontinent and impotent (a relatively common outcome). #4 is only bad if you would have been helped by earlier detection which is a theory often proposed but often doesn't hold up to scrutiny.
Right now the biggest noise is around breast cancer which unfortunately has problems with all four potential outcomes. You can miss aggressive cancers on mammography. It is not at all clear that getting aggressive cancers early affects any change in outcome. There are many, many false positives. There are a number of breast cancers (DCIS for example) that left alone, typically don't do anything.
So the 'preventative medicine' bandwagon needs to be taken down a notch or two. It is not helped at all that most of the bigger players in cancer research and therapy stand to gain by aggressive detection treatment strategies.
Patients, not so much.
Faster! Faster! Faster would be better!
The thing is that cancer is not one disorder, or even just a few disorders. Heart disease can reasonably be considered one disorder (although it is probably more accurately viewed as three or four disorders). There are hundreds of different disorders that we lump together under the term cancer.
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You're leaving out #5:
You find a cancer that is so aggressive that it will kill you no matter what, but you still treat it and the treatment kills you faster or reduces the quality of your remaining life.
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There is inferior bacteria on the interior of your posterior.
Doesn't the TSA offer this service for free?
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It's a fair bit more complex than that.
Genetic damage accumulates _all_ the time, however you have DNA-repair mechanisms of rather amazing complexity that constantly patch things back into their original shape, and in the case they fail they still face down the checkpoints in the mitotic cycle that halts cell divison until damage is either repair or the self-destruct/apoptosis kicks in.
And there's more, if a cell starts to produce foreign proteins these will appear in fragments on its surface, which the immune system will latch onto, and then the cell will face down the subtly named Natural Killer cells which have methods to force the aptotic machinery into action even if the intial stages have somehow mutated into uselessness.
Also, cancer that grows fast will displace itself to the point where necrotic lesions appear, these will result in inflammation, a state usually not very conductive to growth, which may self-limit the cancer(not to mention that inflammation means the presence of immune mediators, a lot of them).
As for chemo, it's not that black and white, there's a very large difference between cancer cancer and chemo and chemo. Certain lymphoma(enormous proliferation of immune cells, circulating) have very close to 100% survival rate, if you enter chemo treatment. Testicle cancer also have a very good prognosis even if metastatized. For a perspective, take a look here http://en.wikipedia.org/wiki/Chemotherapy_protocol
as many as 120,000 to 134,000 of those women either have cancers that are already lethal or
There are a lot of cancers that are incurable, but can still be controlled for a while. Statements like this make it sound as though catching these cancers early and controlling them for a while is a worthless endeavor.
My wife is one year into a battle with a cancer that she has only roughly a 25% chance of surviving with treatment. Without treatment, she would have been dead a few weeks after diagnosis. She is grateful to have spent the past year alive instead of dead, and of course the children and I are also grateful. I guess the point that I'm trying to make here is that treating a cancer that will most likely be lethal still has significant value. None of us would have been very happy if some government bureaucrat had told us that since the cancer was so likely to kill her, they wouldn't bother treating.
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I guess the question is how do you tell the ones that need treatment from the ones that don't before it it too late to treat the ones that do
Histology at the moment. What a trained pathologist can tell from a slide of stained cells is incredible. In the near future, genomic sequencing is what experts seem to be saying. You find a tumor, you get a biopsy, look at it under the microscope and also sequence the DNA of the cancer. Between what the cells look like and the DNA sequence, they'll be able to tell how likely it is to kill you.
There are a number of well-characterized things a cancer cell must do to be really bad, and genomic sequencing will allow a good diagnosis as to what a cancer is doing exactly. If it's just that the cells are growing more than they should, but are otherwise playing by the rules (IE, unlikely to metastasize or start increasing the bloodflow to the tumor, and not in a critical location) keep an eye on it but it may not become a problem ever. If it is expressing several genes that will allow the cells to get into the bloodstream and take root elsewhere, chemotherapy now. Chances are much better that it will spread to critical areas like your lungs or brain and kill you.
But what's the alternative? Just wait until someone's sick enough to warrant a cancer screening?
Or, to be more direct, the problem isn't the _testing_, it the _reaction_. The view of cancer is too binary... You either don't have cancer or you have ZOMG CANCER. It seems to me that by making a third category of 'mostly harmless' we could really do away with #3 altogether. How could we determine that? Early detection and study. Exactly what abandoning screens would make impossible.
Really, this is just about the money, in a couple directions:
First, no doctor is going to volunteer "this is cancer, but it doesn't look dangerous so we'll just monitor the situation" because God help them if that person dies.
Second, people usually spend other people's money (government, 'insurance') on the treatments, so to them it's only 'some side effects vs your life' and not also about 10% of their lifetime earnings too. Guess what they'll take? And so the people paying for these tests have come to realize that they're just a money pit: the (usually negative) test, the (potentially) unnecessary treatment, and finally just the cost of treating real cancer a year or so earlier then you would have had to without the screen for someone that may well die anyway (any they get the pleasure of a year of treatment). All this for how many people that earlier treatment would have helped? Well, that is the point of the study.
But the point is, that it's not the data that's bad, it's a system the encourages people to get knee jerk treatment.
Then there's a particularly nasty subset of #3, you find an essentially harmless cancer like object and treat it aggressively. As a result of long term damage to your immune system and genetic damage from harsh chemo, you develop a lethal cancer that can't be treated. Or you just spend the rest of your shortened life in relatively poor health.
Absolutely! If the statistics show that we're better off without early screening in terms of health outcomes, by all means! We should be doing something else with our time and money than to spend them on ineffective screening.
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That's an incredibly narrow-minded view. If it is shown that some types of screening statistically make you worse off, then it is silly to continue advocating their use in the same way. I'm sorry you had to deal with a traumatic event, but that doesn't make math stop working.
I've lost loved ones to cancer as well, but if early detection doesn't help you, and false positives can really hurt you, then cancer screenings are doing more harm than good and costing society dearly.
I've been growing more wary of early detection, and not just cancer, but all sorts of things. False positives are everywhere in medicine, more commonplace than we'd like to think. It's better to educate people on symptoms, screen only for things that don't have any symptoms (until it's too late), and generally people should live their lives normally and only see a doctor when they actually get sick. Annual check-ups are good for people who are uninformed about their health, or have questions they need answered, but what do they actually do for healthy people? Nothing. What do they do for sick people? Well, those sick people should've made a special appointment when they realized they were sick, not based on an arbitrary annual check-up schedule.
If something hurts, is bleeding, or isn't working right, by all means, go see a doctor, ideally a specialist who knows all about it. If there's nothing wrong, though, you're more likely to become sick going to a doctor's office or hospital than if you just stayed home. Either you'll catch something from another patient who's there legitimately, or you'll become a victim of malpractice or treatment for false positives.
While emergency medicine is based on worst case scenario, the rest of our medical system is all based on probabilities. The same three symptoms could mean you have x, y, or z, but you're treated for y because it's most likely. Only if treatment fails do we consider x or z. It's not a perfect system, but it's the best system for the most number of people, until we devise better tests to differentiate x and z from y. By all means, we should use cold hard statistics to weigh the pros and cons of screening. If the probability of harm is greater than the probability of benefit, regardless of the dangers of untreated cancer, we must advocate less screening.
-mrxak
Onions Will Kill You
First, no doctor is going to volunteer "this is cancer, but it doesn't look dangerous so we'll just monitor the situation"
This is not universally correct. For a run-of-the-mill prostatic adenocarcinoma (your garden variety prostate cancer) there is actually the concept of active surveillance, where the patient gets yearly biopsies to track any progression. If the biopsies show cancer involving more than it should (where should is defined by a variety of factors) then treatment becomes more aggressive (read: prostatectomy).
In your defense however, AFAIK this is one of the only types of cancers were this is true, as the lifetime chance of a male getting prostate cancer verges on 100% (if they live long enough). Certain brain tumors may take a watch-and-see approach as well since their progression is not as well understood and the morbidity associated with various brain surgeries can be pretty high.
Agreed though in that not all cancers are created equal. Knowing which is which though is, as they say, the rub
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My colonoscopy at 53 (3 years late) detected the start of malignant cancer. My gastro guy described my situation as "having *just* missed being hit by the bus. Without treatment, I'd have been dead in less than 5 years, give or take a year.
So, better safe than sorry has become my new motto. The social and economic cost, in the scheme of things, is trivial (That is, if you have health insurance. If you don't, unofficial government policy is the usual de facto homicide applied to the poor).
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without the test you never have the choice between treating and not treating. This sounds like a study conducted by wealthy @$$es to discourage middle class people from seeking medical treatment. I don't see Senators turning down treatment. What was that qoute? "In America, If you get sick better die quick!".
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Unless you are getting yourself screened daily, there is about a 0.0001% chance the x-ray will give you cancer. The reason doctors/etc stand behind the concrete wall when they x-ray you is because they are doing that on a regular basis.
Screening test are not as important as we thought. WRONG. If anything this points to MORE FREQUENT screening of assorted cancers.
Assuming, of course, that your test will detect cancer before its too late. I remember reading a study on mammograms which concluded they were a waste of time because cancers that were going to metastasize had already done so by the time you can detect them on a mammogram. More screening is then just a waste of time, and in fact is counterproductive because repeatedly bombarding tissue with x-rays will cause some amount of cancer that wouldn't otherwise have occurred.
It is not at all clear that getting aggressive cancers early affects any change in outcome.
5 year breast cancer survival rates:
Detected at stage 1: 88%
Detected at stage 4: 15%
Source: http://www.cancer.org/Cancer/BreastCancer/DetailedGuide/breast-cancer-survival-by-stage
You're right, dunno why we bother screening.
However, it is not at all clear that those detected at stage 1 are all the same types as those detected at stage 4. If a significant fraction of those detected at stage one would NEVER progress beyond stage one lets call them "type A", with the aggressive ones called "type B", then it is at least possible that "type A" has a 15% survival rate no matter what stage it is detected, and is responsible for much of the 12% death rate in the early detection pool, as well as the 85% death rate in the later detection pool. Treating the "type A" cancers early could provide no benefit - and since it is benign it makes it look like early detection increases survival rates even if it does not.
To be fair to the original poster, he did say "It is not at all clear that getting aggressive cancers early affects any change in outcome." Your data does not separate out the "aggressive" and "non-aggressive" cancers. Part of the problem is that it is not clear what (if anything) differentiates the different levels of cancer aggressiveness.