We could greatly increase the survival for most cancers if we could detect them much earlier.
“ If it is caught in the early stages then the chances of survival are good, but as the cancer becomes more aggressive and spreads throughout the body (known as metastatic cancer) then survival plummets”
Yes, it is a real problem. Cancer treatment is generally not a walk in the park, and you'd be administering it to people who never would have otherwise need it. Imagine having portions of your body removed and/or receiving brutal treatment for no real purpose. Further, these tests have false positives and even in the best case that could cause undue stress and strain.
It's been a while since I've been in the field, but at least as of several years ago the oncologists I knew were starting to turn against heavy pushes for early screening for these and similar reasons.
My understanding is most people get cancer cells regularly. Possibly every day. The immune system clears them out naturally. The question is how old is a cancer before it becomes a threat worthy of analysis. Obviously one cell is probably not interesting. I think there's evidence even cancers that are large enough to be visible to the naked eye are not typically dangerous. If 99% are harmless, what is the point in early detection? It's an expensive test and expensive doctors visits to mitigate a 1% risk. It's interesting from a research perspective to be sure, but not as a standard of care.
We don't generally treat neoplasms, because we get lots of them, most are of no consequence, and treatments are damaging. We care about the malignant neoplasms where the biological cost of treatment is outweighed by the cost of allowing the malignancy to remain.
If you can reliably distinguish between those malignant neoplasms and "any growing neoplasm in the body", collect your Nobel and enjoy your well-earned message board karma from winning this debate. Since you can't, what you're really doing here is begging the question.
It's not about superstition or fear, it's about resource allocation and common sense. Medical services are finite. Screening and continuous monitoring of every potential tumor in everyone would be crazy time consuming and incredibly wasteful. So let's not.
EDIT: Just to be clear, the idea of accurate early detection is of course a good one. But as of today it is just not viable.
You also have to be careful to quantify "useless," "useless" can mean "doesn't work," but if we are objectively detecting cancers it's hard to say it's "useless."
You also may have one person's life saved for every 20 who were harmed by the screening program - it's still useful for those people who benefited. So yeah, that terminology is problematic.
It's more accurately to speak of a bad screening program "causes more harm than good on a population wide scale."
And, of course, it's important to clarify we are talking about screening the general population who is asymptomatic and at average risk. If you've got symptoms then the topic becomes diagnosis, not screening. If you have an increased risk due to genetic factors, family history, or increased exposure to some cancerogenics then then risks of screening for the general population don't apply to you.
Then why not respond appropriately, and stay aware of cancers but don't treat them until they reach some critical stage? I don't see how intentionally remaining ignorant is helpful.
Because if a localised cancer is destined reach later stages then getting treatment as soon as possible is of the essence - if you wait for it to become malignant before treating it the chances of survival go down.
Often it's impossible to tell right now which asymptotic localised cancers are going to eventually kill the patient if left untreated and which are going to be non-bothersome or even spontaneously regress. They look the same in many cases.
What would you do if your doctor found a cancer and refused to treat it? What do you think most people would do? I reckon most people would shop around until they found a doctor that would treat it. Even if they followed the doctor’s advice, the knowledge they have cancer might be incredibly stressful and distressing.
On a population-wide scale, ignorance may be the best option right now.
If my doctor said "Yes, this is cancer, but it's so small and more likely than not to never become a problem. Come back in two months and we'll check again to make sure it's not becoming a problem", then I would be fine with that answer.
We need tests with lower false positive rates. The problem with catching cancer early is confirming whether you actually have cancer or not. This most often requires invasive biopsies which exposes the patient to significant postop risks and the early detection tests' false positive rates mean that blanket tests of all patients would do far more harm than good. For example, mammograms have a false positive rate of something like 50% and complications happen in something like 30% of surgeries. Multiply that by every possible common cancer and you've got a no-win scenario.
All of our early detection tools are pretty terrible and we can't ethically test everyone for everything so it's all about educating the patients to take a proactive role.
>We need tests with lower false positive rates. The problem with catching cancer early is confirming whether you actually have cancer or not.
This is a big problem, but it's far from the only problem. The other problem is catching cancers that are destined to stay harmlessly in place. So-called "turtles." They are surprisingly common among the population.
South Korea currently has this problem - 15 years of screening has found a massive amount of thyroid cancer, so much so that thyroid cancer is now the most common cancer in Korea. Yet all these extra cancers discovered and treated early hasn't reduced the death rate at all. That means the cancers being detected and treated are destined to have no negative consequences to the patient.
The 50-60% figure is based on ten annual mammograms.
In a given mammogram it's more like 7-12%.
The younger you are, the more likely your positive result will be a false positive. And it also varies based on tissue density (women with more dense breasts have higher false positive rates). The higher false positive rate in younger women is of course why they've shifted screening times, pushing back the suggested start age and or doing every other year instead of every year.
If you recall someone from screening for additional diagnostic views, this is not strictly a false positive as the initial evaluation is definitionally incomplete. However, many would argue the additional views result in additional patient stress and anxiety (I personally do not buy this argument especially if you set expectations at the time of initial image acquisition).
Of the patients who are recalled, maybe 20% proceed to biopsy, of which probably 20% have histologic cancer and another percentage have high risk lesions that are not cancerous per se but are often surgically removed as they either cannot be fully sampled using a minimally invasive technique.
Recall rates are tracked and heavily scrutinized at the individual radiologist level. The targeted recall rate is in the range of 5-10% with the assumption that recalling more than this is being too sensitive and less than this is potentially missing cancer.
Mammography performance is often defined in cancers per 1000 screening exams for a given population.
Realistically, someone needs to proceed to all the way to biopsy (and have it come back negative) to have a real false positive.
Someone being recalled from screening for additional views only to be released as “superimposed tissue” or “benign finding” is not a true false positive. To argue so is being a bit disingenuous.
That was the conventional wisdom for years and it seems obviously true - catch cancer early before it spreads.
Yet when we actually study these things we find out early detection might not be desirable (but also sometimes is). It's complicated and there's a whole lot we don't know.
Also "most cancers" is almost certainly false, more like "some cancers." And at what cost?
>It’s hard to believe in overdiagnosis and overtreatment if you imagine that cancer behaves in a progressive manner: that is, that it arises from one haywire cell that replicates abnormally before inevitably spreading to other parts of the body, eventually killing the person. Let’s call this way of thinking the relentless progression model. In this model, every cancer cell is destined to spread and become lethal, and that’s how doctors have traditionally been taught to think of cancer’s progression.
>Today, thanks to sophisticated cancer genetics and advances in tumor biology, we know that’s not always how it works. Cancer is not a single disease; it’s many. On one end of the spectrum lie cancers that become aggressive and invasive from the start, and on the other end are cancers that remain non-invasive and therefore harmless. Whether a single rogue cell replicates slowly and stays put or goes wild and spreads is determined by a variety of factors that scientists are still working to understand.
>What’s clear is that cancers fall into a few general behavior patterns, which Welch and others have compared to animals that must be kept in the barnyard to prevent a deadly rampage. Papillary tumors are like turtles — they move very slowly and never pose an escape risk. They don’t need screening, because they will never cause trouble. Then there are rabbits, which are eager to hop away to other parts of the body, but can be confined if they’re found and fenced. These are the cancers that can be helped by early detection and treatment. Birds, on the other hand, are so flighty and quick that they can’t be confined. Screening makes no difference for bird cancers, because they’re so aggressive that they can’t be detected before they’ve begun their deadly course.
>No cancer screening has ever eliminated the majority of cancer deaths. Instead, the best screening can do is reign in the rabbits. Birds remain unstoppable, and they’re the ones responsible for most cancer deaths. This is why, Welch says, three decades of mammography have failed to put a dent in the rate of women presenting with metastatic breast cancer upon their initial diagnosis.
“ If it is caught in the early stages then the chances of survival are good, but as the cancer becomes more aggressive and spreads throughout the body (known as metastatic cancer) then survival plummets”
Craig Venter:
https://youtu.be/iUqgTYbkHP8?t=15m37s