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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."
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.
The truth is that all men having power ought to be mistrusted. James Madison
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.
Presumably for the reasons enumerated in the summary. Too many costly, and quite frankly terrifying, false positives. Keep in mind, when you start talk about putting everyone through a screening, whether it be for cancer or HIV or terrorism, your screen had better be crazily accurate. Imagine there's a (really exceptionally good) false positive rate of 0.1% on your hypothetical test, if you give it to every person in the US twice a year you're going to produce 74,000 false positives a year. Or to put it another way, more false negatives than there are cancer deaths.
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.
They don't grade fathers, but if your daughter's a stripper, you fucked up. --Chris Rock
What people always forget when talking about the "government takeover of health care" is that there are already bureaucrats sitting between you and your doctor--the private insurance companies--and you already have limited mobility between providers, due to limited open seasons and pre-existing conditions and whatever else your employer stipulates. But instead of being handled by a government agency overseen by elected officials, you are beholden to a for-profit organization who wants everyone to pay in more than they draw out. While I'm sure there are arguments to be made that efficiency gains can be produced in a properly regulated market versus a single-payer system, I don't think the market we have meets that criteria at the moment. It will be a little better after Obamacare goes into effect, but a lot of the health insurance system is still not working in the best interests of the patients.
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.
When evaluating what works and what doesn't, you have to tread very carefully. Sure, most people^Wgeeks know about double blind studies, but that's just the tip of the iceberg. The second edition of Testing Treatments came out recently (available as a free pdf on the website, although I bought it to support the authors) that explains the problems in an understandable language while not dumbing down the issues. The book comes with the recommendation of well known epidemiologists like Ben Goldacre, of Bad Science.net fame.
To talk about the specifics of screening, check out Chapter 4. To recap the main points there, for screening to be worthwhile you have to look at several factors:
The problem with lots of screening is that on the level of the population it can lead to more harm than good overall for a lot of different diseases, because of false positives, because of our psychological makeup that we'd prefer surgery for even harmless varieties of lumps in our bodies, etc. (see detailed examples in the book). In a lot of cases it happened that screening was introduced before the effectiveness of screening was established in a trial, then later trials showed that the screening was ineffective in reducing deaths or harm.
The bottom line is that well designed trials should be conducted and based on the systemic review of those trials it should be decided whether to conduct screening or not, based on whether it's improving health outcomes or not. A lot of trials don't improve outcomes.
It takes a man to suffer ignorance and smile
Be yourself no matter what they say
Your link shows no evidence that "AFP is a crummy screening test". Were you hoping that nobody clicked the link, and just took your word that it was correct?
My impression is that ColdWetDog was hoping whoever clicked the link would follow Wikipedia's explanation of how the statistics of screening tests work, and using that explanation, understand the logic of why AFP is not used as a general cancer screen by filling in the blanks themselves.
But that's ok, maybe you didn't understand him, so let me elaborate a bit in steps. The "Specificity" of the AFP test is the percentage of True Negatives (patients without cancer), divided by Reported Negatives (AFP tested negative). Now, the specificity of the AFP assay varies with the laboratory, cut-off criteria used, and particular cancer -- but something like 90% is reasonable for an AFP test (better for some cancers, worse for others, not applicable for many). That sounds good, right?
Well, next step is figuring out your Positive Predictive Value. The interesting thing about this parameter, is it varies with Prevalence. If you define your tested population as a group in which you already have reason to suspect cancer, you can get a pretty decent PPV. Now, elevated AFPs are rare in the healthy general population. Thing is -- while it might not seem that way emotionally -- statistically, cancer is also considered a rare health condition (from an epidemiological standpoint). The net result is most tumor biomarkers applied to the general population, end up with low PPVs -- even tests with specificities of 90+% can end up with PPVs in the single digits or less.
While I don't have a specific link for AFP, the general state of population-wide cancer biomarker screening is not good: http://www.nature.com/news/2011/110323/full/471428a.html
but perhaps you are a genuine "shill" for one of the big pharmaceutical companies.
Oh, you were just shitposting. Carry on then.
We could break apart the back room collective bargaining and price fixing and actually make health care something that people actually pay for, like car insurance and automotive services. That way, at least, we can see some competition for price and maybe people will even understand the resources they waste every time they go to the doctor about a cold. (Well, at least after they paid $80 to hear the doc say "It's a cold, drink some juice and get some rest" they'll think twice before doing it again.)
This is a common fallacy -- that the costs of going to doctors for minor discretionary ailments are a significant part of health care costs. As the economist Paul Krugman has explained, the major expenses in health care aren't $80 visits to the doctor, but $50,000 and $100,000 cancers, $20,000 a year lifelong treatments for diabetes, $50,000 a year lifelong treatments for multiple sclerosis, $50,000 and $100,000 heart bypass operations.
Actually, there have been many studies over at least 40 years to see whether charging patients more would produce better -- or even cheaper -- care. They all failed. Look up the Rand Health Insurance Experiment in Wikipedia. Patients who had greater copayments put off necessary care, like blood pressure medication (probably the most cost-efficient intervention we have).
U.S. corporations like IBM tried imposing co-payments on their employees, and they ended those policies when they found that they wound up spending *more* money. Patients with asthma put off maintenance care, and wound up going to the hospital more.
Health insurance isn't like car insurance. If your car is damaged, you know what the problem is and you know what's going on. If your doctor tells you that you have a disease you never heard of, and that you have to treat it right away, you don't know what's going on. It will take you more than a day of Google searches to find out.
If a nurse tells you, "You should go to the hospital right away. It could be life-threatening," what are you going to do? Look it up on the Internet?
Making health care decisions is like a graduate-level exam with questions you're unlikely to understand, and if you get one question wrong, you die.
It would also help the problems with cancer screening: once people see a $10,000+ price tag on treating that maybe-dangerous tumor they'll definitely give waiting and seeing a thought.
Ridiculous. The main thing a cancer patient wants to know is whether (or how long) he's going to live. The only concern about treating a tumor is (1) whether it really is a tumor that has to be treated and (2) what the best treatment is.
Cancer chemotherapy causes heart failure and other cancers. Is the risk of death from treatment greater than the risk of death from no treatment? Nobody takes doxorubicin just because they can get it free.
I know people who are doing watchful waiting, because their doctors think it's one of those false positives. I've talked about the decisions with them.
$10,000 doesn't enter into the decision. How much is your life worth?