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No Evidence that Cancer Screening Saves Lives

Posted January 13, 2016 1:00 PM by Quasar
Pathfinder Tags: cancer screening mortality

An article in the British Medical Journal argues that screening for cancer has never been shown to save lives. The authors focus on the difference between overall mortality (the death rate from any cause) and disease specific mortality (the death rate caused specifically by a disease). They say that while there is evidence to suggest that screenings reduce disease specific mortality, overall mortality is either unchanged or negatively affected.

The authors point to, among others, a review of meta-analyses of cancer screening trials in the International Journal of Epidemiology, which found that while some trials showed reductions in disease specific mortality, none showed reductions in overall mortality.

There are two main reasons mentioned for the discrepancy between disease specific mortality and overall mortality. The first is that studies might be underpowered to detect a small overall mortality benefit. (Underpowered studies are those that have a low probability of detecting an effect of practical importance.) The second is that disease specific mortality reductions may be offset by deaths due to the downstream effects of screening.

Given that the overall goal of a person considering a cancer screening is to reduce their risk of dying, the possible harmful effects of screening need to be considered in addition to potential benefits. Screenings can cause harm if they result in false positives (abnormal results that turn out to be normal) or overdiagnosis (harmless cancers that never cause symptoms). For instance, false positive results from prostate cancer screenings contribute to more than one million prostate biopsies a year, which are linked with serious harm, including admission to hospital and death. False positive results affect between 12-13% of all men who have undergone three or four screening rounds with PSA, and over 60% of women undergoing screening mammography for a decade or more.

Do you plan to get screened for cancers? Are you worried about false positives, overdiagnosis of non-harmful cancers, or detection of incidental findings leading to treatment that you don't need and could cause you harm?

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Guru
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#1

Re: No Evidence that Cancer Screening Saves Lives

01/13/2016 5:26 PM

Wow. I'm shocked that cancer screening hasn't led to immortality!

Ok, yes, I'm being facetious. But there is a larger point here that appears not to have been addressed: Does cancer screening lead to therapies that maintain or improve quality of life and allow patients to live longer?

I think most people would want cancer screening if early detection means that they can avoid pain, avoid a radical change in lifestyle, or avoid becoming a burden to their families.

I had a young family member who avoided any regular check-ups with the doctor until at one point he became very ill, and was diagnosed with stage 3 lung cancer. He died within a few months. I feel confident that had he seen a doctor a year or two earlier, his cancer would have been detected in an early stage and he would have had lived at least a few years longer. He also would have had more time to plan the disbursement of his estate, sparing his family that financial headache.

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#2

Re: No Evidence that Cancer Screening Saves Lives

01/13/2016 7:40 PM

The problem with statistics is that they look at whole populations. As an individual, if 99 out of 100 screenings were wasted, what if you are a 1%'er?

However, I do believe that a measured approach is called for based on family history/genetics, lifestyle, general overall health, and (gasp) one's ability to pay.

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#3

Re: No Evidence that Cancer Screening Saves Lives

01/14/2016 5:16 AM

This is a classic case of using statistics as smoke and mirrors to produce a headline or to justify an otherwise unjustifiable research grant. The two morality rates are not directly comparable. The disease specific mortality rate clearly shows that screening works.The overall mortality rate is calculated in a different way. We all die at some point so the number of deaths is fixed at 100% (ignoring Lyndor's elixir of life which is so expensive they have yet to make their first sale) The mortality rate therefore depends on the proportion of the population dying in any one year which is a function of average lifespan. As the first generation of cancer survivors has passes through the average lifespan increases. Thereafter further cancer survivors merely sustain the increased lifespan but do nothing to increase it further. So the mortality rate variation based on cancer survivors alone shows no change, which is what was observed but is also what was plainly obvious without an expensive study to prove it. Further it would not be possible to isolate one a single contributory factor to overall mortality. The UK population is 64½ million, and rising at approximately ½ million per year. A substantial portion of the rise is caused by immigration or first generation offspring of immigrants coming from countries where to average lifespan is lower than the UK's. This skews the figures obscuring any underlying increase in the lifespan of the long established population.

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#4

Re: No Evidence that Cancer Screening Saves Lives

01/14/2016 9:48 AM

"They say that while there is evidence to suggest that screenings reduce disease specific mortality, overall mortality is either unchanged or negatively affected."

"...screenings reduce disease specific mortality..." Screening for lung cancer allows early treatment and reduced mortality from lung cancer, screening for skin cancer allows early treatment and reduced mortality from skin cancer, etc. In other words, "If we're looking for it and we find what we're looking for, we can treat it." aka, "It works."

"...overall mortality is either unchanged or negatively affected..." If we're screening for cancers and we find them, and the person later dies from a cancer-related symptom, it's marked off as "Death from cancer," If we don't look and an undiagnosed cancer kills the patient, it's marked off as "Natural Causes" or "Cause Unknown."

That one sentence spun the statistics so hard you could hook up a generator to it and use it to power the Great Ormond Street Hospital(1) for a year.

Now I need to check out the original article to see how bad it really is...

Notes:

  1. The Children's Hospital that owns the 'perpetual copyright(2)' for the play Peter Pan: the Boy who Wouldn't Grow Up
  2. Not a 'true' copyright, as they do not have creative control over the play or the characters, and does not include the right to refuse permission to use it. The 'copyright' only grants GOSH royalty payments on productions of the play(3).
  3. And the royalty payments are going to a Children's Hospital, for crying out loud. You have to be a Grade A, Double-Refined, Triple-Filtered A-Hole to not want to give a Children's Hospital their fair share payment.
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The Engineer
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#5

Re: No Evidence that Cancer Screening Saves Lives

01/14/2016 9:57 AM

I wonder if Cancer Screening has improved in the last decade. I would expect it has, and in view of improving techniques/detection, will these results still hold up? What was the timeframe of the analysis? I would imagine that they must consider data going back decades when screening technology wasn't nearly as good and probably more harmful.

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#6

Re: No Evidence that Cancer Screening Saves Lives

01/14/2016 10:50 AM

There is no cure for cancer...except when you are misdiagnosed, which happens often...

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#9
In reply to #6

Re: No Evidence that Cancer Screening Saves Lives

01/14/2016 2:03 PM

While it is true that there is no 'magic pill' that makes all the cancerous cells in your body die at the same time, while leaving your healthy cells along, there are several ways to effectively remove cancer from a person's body, depending on the type of cancer, and how early it is spotted.

An extreme case for 'easy to get rid of' is melanoma, skin cancer. if spotted early, before it metastazises, the doctors can just trim the tumor off, taking a little 'healthy skin' all around it (covering the buffer zone of 'we know the main tumor mass stops there, but has it sprouted 'tendrils' we can't quite see yet?') and then stitching the 'extraction site' closed.

Now if you get bone cancer, marrow cancer, or blood cancer, then it's a lot harder to get rid of, you may be leaving entire limbs behind when you finish the treatment, and a tumor deep in the brain, there's no way to even GET to it without turning the patient into a vegetable.

But the blanket statement of 'There is NO cure for cancer' is about as accurate as saying 'I have never seen a black sheep myself, therefore there are NO black sheep.'

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#10
In reply to #9

Re: No Evidence that Cancer Screening Saves Lives

01/14/2016 6:53 PM

Surgery isn't a cure, it's a delaying tactic....

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#11
In reply to #10

Re: No Evidence that Cancer Screening Saves Lives

01/15/2016 9:15 AM

SE, EVERYTHING in life is either a delaying tactic in the slow march towards the grave, or a headlong rush to get to the grave quicker.

And with the cancers that have an external source (Melanoma, for example, tends to be caused by excessive UV damage to skin cells, and lung cancer has 'smoking' as a strong factor in its 'causes' list) if you remove the source of the damage, (by limiting your unprotected sun exposure, or by quitting smoking) the odds of remission decrease significantly.

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#7

Re: No Evidence that Cancer Screening Saves Lives

01/14/2016 1:09 PM

Take it from a survivor -- and from the American Cancer Society: screening methods have improved dramatically and are indeed life-saving.

"Death rates from breast cancer have been declining [in the U.S.] since about 1989, with larger decreases in women younger than 50. These decreases are believed to be the result of earlier detection through screening and increased awareness, as well as improved treatment."

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#8

Re: No Evidence that Cancer Screening Saves Lives

01/14/2016 1:49 PM

Screening technology continues to advance, thankfully; a market with the potential for tens of billions of dollars in revenue encourages that.

A new company called GRAIL, funded by $100 million from, among others, Microsoft co-founder Bill Gates and Amazon founder Jeff Bezos aims to offer blood tests for around $500 for early detection of cancer by 2019. The blood tests would be unique among current widespread screening techniques in that they would use intensive DNA sequencing to look for patterns of telltale mutations.

Parent company Illumina CEO Jay T. Flatley said that this new technique would be useful because GRAIL would figure out cancer's mutation signatures by doing DNA sequencing on 30,000 to 50,000 people over time, a portion of whom would have or develop cancer.

Hopefully this screening technique will be more effective at countering the false positives and overdiagnoses common among cancer screenings today.

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Guru

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#12

Re: No Evidence that Cancer Screening Saves Lives

01/15/2016 9:33 AM

Surgery = take enough out and you STILL die, only sooner rather than later.

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#13

Re: No Evidence that Cancer Screening Saves Lives

01/15/2016 9:05 PM

Bogus.

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