Ken Lee’s result that high med spending states tend to have more cancer deaths inspired me to look up the med lit on cancer screening. I turned to Cochrane Reviews, high quality med lit reviews. Here are the reviews I found on cancer screening:
I know many believe the pap test is the most effective screening test in history. I can't agree...There are no RCT's for pap testing and also, this was always a rare cancer, in decline before screening started and those factors are still having an effect on the incidence and death rate. Dr Gilbert Welch points out things like better hygiene and less sexually transmitted disease in his book, "Over-diagnosed". I'd add more hysterectomies (1 in 3 US women will have one by age 60!), fewer women smoking, better condoms etc...It's true that stomach cancer has also fallen by a similar or greater margin with no screening at all, yet you can bet if there was a screening test, they'd be grabbing the credit.
The thing that writes off cervical screening for me: vast over-detection and potentially harmful over-treatment. I also hate the way cancer screening is regarded as compulsory for women, elective for men. Women don't get balanced and complete information and our legal right to give informed consent for cancer screening is dismissed...in the States and Canada women are routinely coerced into cancer screening and often, over-screening and reckless screening. (screening women not yet sexually active from age 21) I know American doctors refuse women birth control pills, HRT, migraine meds and even all medical care until they agree, to not only cancer screening, but completely unnecessary and potentially harmful breast and gyn exams. (these exams are not recommended in asymptomatic women here and in many other countries)There is a double standard in cancer screening.
In Australia we also over-screen (not as badly as the States) and there is zero respect for informed consent (for women) - our GP's even receive an UNDISCLOSED target payment for pap testing (about to be raised to 65% of eligible patients)...this is unethical as it creates a potential conflict of interest. These payments were recently changed in the UK, thanks to the work of some amazing advocates for informed consent for women.
Here we screen women from 18 (sometimes earlier) knowing this is of no benefit, but exposes these women to harm and great worry.
"No country in the world has shown a reduction in the incidence of or the mortality from cervical cancer in women under 30, irrespective of cervical screening. Many countries do not perform cervical screening on women under 30"..."Cervical cancer screening" a handout for doctors (not women!) in "Australian Doctor" 2006 by Assoc Prof Margaret Davy and Dr Shorne.Still we continue to test young women....
Finland has the lowest rates of cc in the world and sends the fewest women for colposcopy/biopsies (fewer false positives) - they offer 5 to 7 tests, 5 yearly from age 30. (even this schedule sends 35%-55% at some stage for follow-up)Australia often boasts about having the lowest mortality rate in the world, but we keep our shameful over-detection and over-treatment rates under wraps. This low rate is achieved at a terrible cost paid by the healthy population of women - the more than 99% who'd never have an issue with this cancer and all with no informed consent.
Dr Angela Raffle, UK screening expert showed that 1 in 3 pap tests will be "abnormal" in women under 25 - false positives caused by normal changes in the maturing cervix and from harmless and transient infections. Cervical cancer is rare, very rare before 30 and screening doesn't change the incidence or death rate in young women anyway.It is unethical to test women under 30 and definitely before 25 and to test any woman without informed consent.
We also test 2 yearly and this means lots of false positives for no additional benefit - it's over-screening.77% is the lifetime risk of referral for colposcopy and usually some sort of biopsy to cover a 0.65% lifetime risk of cervical cancer. Take out false negative cases and considering other factors are affecting the incidence and death rate - fewer than 0.45% of women are helped (assuming any woman is helped) The States it's even higher - lifetime risk of referral - 95%...(DeMay article at Dr Sherman's site)This amount of over-detection and over-treatment IMO, makes this testing unsuitable for population screening. I don't believe it would be approved today.Now we have a program that is highly lucrative, very political and highly emotive....it helps few and harms (to some degree) many....Some women end up worse off after unnecessary biopsies and procedures like LEEP - cervical stenosis, (infertility, infections, endometriosis and may need surgery if the cervix is scarred shut) cervical incompetence - miscarriages, high risk pregnancy that may require cervical cerclage, more c-sections, premature babies and psych/psychosexual issues.No one seems to care about these women and there are lots of them - the entire focus is on screening and the incidence and death rates for this rare cancer.My own younger sister had a cone biopsy after a false positive pap test - a devastating experience.
It's the same with mammograms - we don't get honest and complete information and there is no respect for informed consent.Thankfully, the UK has some great people prepared to speak up and warn women of the risks. Professor Michael Baum, UK breast cancer surgeon gave another informative lecture at UCL recently, "Breast cancer screening: the inconvenient truths" - at the Medphyzz site.It's also possible to get to the facts behind cervical screening - Dr Joel Sherman's patient privacy site under women's privacy issues has lots of great references, including research by Angela Raffle. "1000 women need regular smears for 35 years to save one woman from cc" (BMJ:2003/4) plus over-detection and over-treatment rates.
It's hard to understand why we spend a small fortune "fighting" this rare cancer when there are FAR greater threats to our lives out there...it says to me that these programs have little to do with our health. The priorities are skewed by pressure/lobby groups, political and vested interests. ($$$)I think cancer screening is a great threat to our health, rights and lives.I made an informed decision, as a low risk woman, not to have pap testing more than 25 years ago and more recently, rejected mammograms. I didn't get the information I needed from my doctor.More than ever before we need to do our own reading, spread the word and make informed decisions about our health care. I don't give a damn about screening targets or my GP's incentive payment...Is this really in MY best interests?
Can it also be assumed that a certain percentage of people who seek screenings (perhaps a large percentage) are taking action and getting screened specifically because they know that cancer runs in their family. And those who don't get screened probably aren't worried because it does not run in their families.
So, screened people who ended up with cancer mortality versus non-screened people who ended up with cancer mortality seems misleading to me.
Maybe there should be a study on the effectiveness of screenings, specifically for people who have cancers that run in their family and a separate study for the same thing specific to people who don't have cancers that run in their families.
My guess is that if you looked at the data that way, both data sets would show that screenings helped.
We shouldn't be too quick to credit colonoscopy for a reduction in incidence and mortality from colon cancer. incidence and mortality of stomach cancer has plumetted something like 80 percent in the last 50 years, and there is no screening for it. Docs who do colonoscopies have found an absolute gold mine, but it's completely unclear whether their patients are helped at all.
Weight loss interventions are even more useless than cancer treatments. As far as I am aware, the only weight loss intervention that has been clinically proven to result in long-term weight loss is stomach surgery. Every single diet-based approach anyone has ever tried has consistently failed.
@BlueStreak:Is it possible for prostate cancer to be detected (and prostate cancer deaths prevented) through digital exam? In principle, yes. I truly hope that this was true for you, and that the medical care you received was beneficial for your health.However, based on what we think we know from the best studies we have, most likely it was not. When considering disease screening, it helps (at least for me) to think about the small percentage of screened patients who we actually end up helping…1. Most patients screened will have a negative result, with only a small minority having evidence of disease (so a lot of unnecessary tests).2. Of those with a positive screen, only a few will go on to have cancer on biopsy (so a lot of unnecessary biopsies).3. Of those with positive biopsies, we have to subtract those patients whose cancer never would have hurt them anyway (and with prostate cancer, we know this is a very high % of cases), because those people won’t benefit from any treatment they go on to receive.4. Of those with dangerous cancer, subtract all those who would not benefit from EARLY treatment – maybe at some later point the asymptomatic cancer detected on exam would start producing urinary obstruction, at which point it may still be curable (and therefore the patient gains no benefit from having found it earlier). 5. Also subtract people for whom it is already “too late” for helpful treatment at the time of screening (this is true of a great number of young men who get prostate cancer).
For prostate cancer in particular, the remaining number who will actually benefit from having been screened is quite small (if present at all). Furthermore, if we make the assumption that there ARE a few people in there who have a potentially lethal cancer cured, then in light of the all-cause mortality data (which shows no benefit to screening), then the logical conclusion would have to be that the small number we help is being offset by an equal number of people being harmed in the course of aggressive medical treatment.
When also considering the discomfort, cost, complications, and side effects of the screens, biopsies, and surgeries, the deal looks less and less appealing.
You ask if we are “just supposed to roll the dice and hope for the best”. I really wish I had a better answer to that question than “yes.” If we ever end up discovering a different, better test that actually helps save lives, I will be the first to start offering it to as many of my patients as I can. In the mean time, given the current state of prostate cancer screening, my own personal choice would indeed be to avoid it.
Statistically, 10-year survival rates in huge cohort studies of prostate cancer indicate no treatment has a better survival rate than "no treatment". Going in, you couldn't know which individual in the study you would be. You still can't. The choice you made was for a published 10-year survival rate, either with the surgery you had and it's attendant side-effects, or without it. This is a bitter pill for both the patients and their doctors, the latter of whom have a vested reason to ignore the statistics. Happily, although thousands of Americans die from prostate cancer each year, they represent a very small portion of those with the disorder.
Don't forget that cervical cancer screening has been scaled WAY back due to the understanding of the relationship between HPV, abnormal Pap smears, and cancer.
For decades, young women who were newly sexually active were subjected to further diagnostic procedures which can damage the cervix and cause problems in subsequent pregnancies. It turns out that most HPV infections resolve without treatment within 2 years.
Also, many women oddly perceive a normal Pap as a certificate of good health. After all, if that's what we continually test for, that's obviously the most worrisome health concern, right?
If the amount of time, effort, and money devoted to screening for cancer in the US was instead directed toward weight loss, we would be healthier.
There's a reason that GIs build stand-alone colonoscopy suites and book back-to-back procedures in assemby-line fashion: They're cash cows.
Colonoscopies are standard treatment because they make the most money for assorted actors (GIs, hospitals, equipment manufacturers), not necessarily because they find cancer in its early stages or improve patient outcomes. There no evidence of these benefits.
Within the past two years, meta-analysis (albeit with some methodological flaws) has show very little benefit of screening colonoscopies, especially for right-sided cancers. Left sided-cancers are better detected, and sigmoidoscopy is perhaps an adequate screening tool given the meta-analysis. But, that procedure costs about $1500 less than a colonoscopy though it is arguably just as effective.
Perhaps worse for patients, routine colonoscopies can lead to a false sense of security wherein patients ignore signs of colon cancer because they've recently been given a clean bill of health.
Screening scopes are almost certain to be a thing of the past as companies improve and certify DNA testing for colon cancer, as has been done in Germany and other European countries.
In general I agree completely that screening is overrated -- my teaching soundbite on it is that screening is the opposite of treatment, since it takes healthy people and makes them sick.
However, I think two of your examples are wrong at least in part.
There's good evidence that the Cochrane Breast Cancer was wrong to discard the trials it claimed had inadequate randomization. See the very detailed analysis by Freedman, Pettiti, and Robins. The authors aren't pro-screening ideologues -- two of them are statisticians and so predisposed not to believe in screening, and Diana Pettiti was co-chair of the panel that, last year, recommended against routine mammography before age 50.
As someone pointed out above, even though ordinary x-ray screening doesn't work for lung cancer, there is now good evidence for CT-scan for lung cancer in smokers and former smokers. I was surprised by this when it came out, but the results are pretty clear.
Re: Prostate cancer testing, you say that "these practices should be ended as soon as possible." In March 2004, at age 54, my primary physician thought my prostate felt "asymmetrical", my urologist concurred, a biopsy came back positive and I had my prostate removed. So far, so good. I understand that many prostate cancers never fully develop, and some are extremely long-developing, but are you saying that I should NOT have had testing done? Are we just supposed to roll the dice and hope for the best? What if I didn't test and I turned out to be too dead to be writing this response? That's not really an acceptable outcome in my opinion.
Even if a type of cancer screening is shown to improve cancer mortality, or even all-cause mortality, even THAT would not be evidence enough to do it. It would also have to be a better expenditure of resources than the next best use of those resources. So if the benefit is small or the cost huge, the statistically significant mortality benefit may not be enough.
Having had cancer myself, I recall that I spent a lot of time considering moving to cities with outstanding cancer clinics. Ultimately, I found what I needed to survive at home in the Chicago area, but if I had relapses and thus needed a last ditch stem cell transplant, I probably would have gone to a state with a state of the art cancer center, and I probably would have died in that state.
According to a quote (with favorable comment) on Overcoming Bias last year: "The evidence strongly suggests that students learn better when they are not graded and certainly not when they are graded on a curve." Using similar reasoning, we can conclude that being part of a randomized controlled study makes medical care less effective.
It'd be considered unethicial to not screen for cervical cancer at this point considering the strong observational data.(ex: http://www.ncbi.nlm.nih.gov...
Almost all of the women who get cervical cancer in the screening era are either from developing countries without screening programs, or women from developed countries who do not regularly getting screened.
It's a shame this wasn't tested in a RCT before it became standard practice, but I doubt you could find a medical researcher or ethicist that would allow women to be in a placebo arm now. I think similar points would be made about colonoscopies. We need further advocation for evaluating screening tools with RCTs before they become standard clinical practice though considering the issues we have with the other cancers (partartically prostate)
Overall, I think you're making an important point but your sweeping generalization that all types of cancer screening is off base and (unfortunately) likely discredits the whole argument in many reader's minds.
I know many believe the pap test is the most effective screening test in history. I can't agree...There are no RCT's for pap testing and also, this was always a rare cancer, in decline before screening started and those factors are still having an effect on the incidence and death rate. Dr Gilbert Welch points out things like better hygiene and less sexually transmitted disease in his book, "Over-diagnosed". I'd add more hysterectomies (1 in 3 US women will have one by age 60!), fewer women smoking, better condoms etc...It's true that stomach cancer has also fallen by a similar or greater margin with no screening at all, yet you can bet if there was a screening test, they'd be grabbing the credit.
The thing that writes off cervical screening for me: vast over-detection and potentially harmful over-treatment. I also hate the way cancer screening is regarded as compulsory for women, elective for men. Women don't get balanced and complete information and our legal right to give informed consent for cancer screening is dismissed...in the States and Canada women are routinely coerced into cancer screening and often, over-screening and reckless screening. (screening women not yet sexually active from age 21) I know American doctors refuse women birth control pills, HRT, migraine meds and even all medical care until they agree, to not only cancer screening, but completely unnecessary and potentially harmful breast and gyn exams. (these exams are not recommended in asymptomatic women here and in many other countries)There is a double standard in cancer screening.
In Australia we also over-screen (not as badly as the States) and there is zero respect for informed consent (for women) - our GP's even receive an UNDISCLOSED target payment for pap testing (about to be raised to 65% of eligible patients)...this is unethical as it creates a potential conflict of interest. These payments were recently changed in the UK, thanks to the work of some amazing advocates for informed consent for women.
Here we screen women from 18 (sometimes earlier) knowing this is of no benefit, but exposes these women to harm and great worry.
"No country in the world has shown a reduction in the incidence of or the mortality from cervical cancer in women under 30, irrespective of cervical screening. Many countries do not perform cervical screening on women under 30"..."Cervical cancer screening" a handout for doctors (not women!) in "Australian Doctor" 2006 by Assoc Prof Margaret Davy and Dr Shorne.Still we continue to test young women....
Finland has the lowest rates of cc in the world and sends the fewest women for colposcopy/biopsies (fewer false positives) - they offer 5 to 7 tests, 5 yearly from age 30. (even this schedule sends 35%-55% at some stage for follow-up)Australia often boasts about having the lowest mortality rate in the world, but we keep our shameful over-detection and over-treatment rates under wraps. This low rate is achieved at a terrible cost paid by the healthy population of women - the more than 99% who'd never have an issue with this cancer and all with no informed consent.
Dr Angela Raffle, UK screening expert showed that 1 in 3 pap tests will be "abnormal" in women under 25 - false positives caused by normal changes in the maturing cervix and from harmless and transient infections. Cervical cancer is rare, very rare before 30 and screening doesn't change the incidence or death rate in young women anyway.It is unethical to test women under 30 and definitely before 25 and to test any woman without informed consent.
We also test 2 yearly and this means lots of false positives for no additional benefit - it's over-screening.77% is the lifetime risk of referral for colposcopy and usually some sort of biopsy to cover a 0.65% lifetime risk of cervical cancer. Take out false negative cases and considering other factors are affecting the incidence and death rate - fewer than 0.45% of women are helped (assuming any woman is helped) The States it's even higher - lifetime risk of referral - 95%...(DeMay article at Dr Sherman's site)This amount of over-detection and over-treatment IMO, makes this testing unsuitable for population screening. I don't believe it would be approved today.Now we have a program that is highly lucrative, very political and highly emotive....it helps few and harms (to some degree) many....Some women end up worse off after unnecessary biopsies and procedures like LEEP - cervical stenosis, (infertility, infections, endometriosis and may need surgery if the cervix is scarred shut) cervical incompetence - miscarriages, high risk pregnancy that may require cervical cerclage, more c-sections, premature babies and psych/psychosexual issues.No one seems to care about these women and there are lots of them - the entire focus is on screening and the incidence and death rates for this rare cancer.My own younger sister had a cone biopsy after a false positive pap test - a devastating experience.
It's the same with mammograms - we don't get honest and complete information and there is no respect for informed consent.Thankfully, the UK has some great people prepared to speak up and warn women of the risks. Professor Michael Baum, UK breast cancer surgeon gave another informative lecture at UCL recently, "Breast cancer screening: the inconvenient truths" - at the Medphyzz site.It's also possible to get to the facts behind cervical screening - Dr Joel Sherman's patient privacy site under women's privacy issues has lots of great references, including research by Angela Raffle. "1000 women need regular smears for 35 years to save one woman from cc" (BMJ:2003/4) plus over-detection and over-treatment rates.
It's hard to understand why we spend a small fortune "fighting" this rare cancer when there are FAR greater threats to our lives out there...it says to me that these programs have little to do with our health. The priorities are skewed by pressure/lobby groups, political and vested interests. ($$$)I think cancer screening is a great threat to our health, rights and lives.I made an informed decision, as a low risk woman, not to have pap testing more than 25 years ago and more recently, rejected mammograms. I didn't get the information I needed from my doctor.More than ever before we need to do our own reading, spread the word and make informed decisions about our health care. I don't give a damn about screening targets or my GP's incentive payment...Is this really in MY best interests?
Can it also be assumed that a certain percentage of people who seek screenings (perhaps a large percentage) are taking action and getting screened specifically because they know that cancer runs in their family. And those who don't get screened probably aren't worried because it does not run in their families.
So, screened people who ended up with cancer mortality versus non-screened people who ended up with cancer mortality seems misleading to me.
Maybe there should be a study on the effectiveness of screenings, specifically for people who have cancers that run in their family and a separate study for the same thing specific to people who don't have cancers that run in their families.
My guess is that if you looked at the data that way, both data sets would show that screenings helped.
We shouldn't be too quick to credit colonoscopy for a reduction in incidence and mortality from colon cancer. incidence and mortality of stomach cancer has plumetted something like 80 percent in the last 50 years, and there is no screening for it. Docs who do colonoscopies have found an absolute gold mine, but it's completely unclear whether their patients are helped at all.
Weight loss interventions are even more useless than cancer treatments. As far as I am aware, the only weight loss intervention that has been clinically proven to result in long-term weight loss is stomach surgery. Every single diet-based approach anyone has ever tried has consistently failed.
@BlueStreak:Is it possible for prostate cancer to be detected (and prostate cancer deaths prevented) through digital exam? In principle, yes. I truly hope that this was true for you, and that the medical care you received was beneficial for your health.However, based on what we think we know from the best studies we have, most likely it was not. When considering disease screening, it helps (at least for me) to think about the small percentage of screened patients who we actually end up helping…1. Most patients screened will have a negative result, with only a small minority having evidence of disease (so a lot of unnecessary tests).2. Of those with a positive screen, only a few will go on to have cancer on biopsy (so a lot of unnecessary biopsies).3. Of those with positive biopsies, we have to subtract those patients whose cancer never would have hurt them anyway (and with prostate cancer, we know this is a very high % of cases), because those people won’t benefit from any treatment they go on to receive.4. Of those with dangerous cancer, subtract all those who would not benefit from EARLY treatment – maybe at some later point the asymptomatic cancer detected on exam would start producing urinary obstruction, at which point it may still be curable (and therefore the patient gains no benefit from having found it earlier). 5. Also subtract people for whom it is already “too late” for helpful treatment at the time of screening (this is true of a great number of young men who get prostate cancer).
For prostate cancer in particular, the remaining number who will actually benefit from having been screened is quite small (if present at all). Furthermore, if we make the assumption that there ARE a few people in there who have a potentially lethal cancer cured, then in light of the all-cause mortality data (which shows no benefit to screening), then the logical conclusion would have to be that the small number we help is being offset by an equal number of people being harmed in the course of aggressive medical treatment.
When also considering the discomfort, cost, complications, and side effects of the screens, biopsies, and surgeries, the deal looks less and less appealing.
You ask if we are “just supposed to roll the dice and hope for the best”. I really wish I had a better answer to that question than “yes.” If we ever end up discovering a different, better test that actually helps save lives, I will be the first to start offering it to as many of my patients as I can. In the mean time, given the current state of prostate cancer screening, my own personal choice would indeed be to avoid it.
Statistically, 10-year survival rates in huge cohort studies of prostate cancer indicate no treatment has a better survival rate than "no treatment". Going in, you couldn't know which individual in the study you would be. You still can't. The choice you made was for a published 10-year survival rate, either with the surgery you had and it's attendant side-effects, or without it. This is a bitter pill for both the patients and their doctors, the latter of whom have a vested reason to ignore the statistics. Happily, although thousands of Americans die from prostate cancer each year, they represent a very small portion of those with the disorder.
Don't forget that cervical cancer screening has been scaled WAY back due to the understanding of the relationship between HPV, abnormal Pap smears, and cancer.
For decades, young women who were newly sexually active were subjected to further diagnostic procedures which can damage the cervix and cause problems in subsequent pregnancies. It turns out that most HPV infections resolve without treatment within 2 years.
Also, many women oddly perceive a normal Pap as a certificate of good health. After all, if that's what we continually test for, that's obviously the most worrisome health concern, right?
If the amount of time, effort, and money devoted to screening for cancer in the US was instead directed toward weight loss, we would be healthier.
There's a reason that GIs build stand-alone colonoscopy suites and book back-to-back procedures in assemby-line fashion: They're cash cows.
Colonoscopies are standard treatment because they make the most money for assorted actors (GIs, hospitals, equipment manufacturers), not necessarily because they find cancer in its early stages or improve patient outcomes. There no evidence of these benefits.
Within the past two years, meta-analysis (albeit with some methodological flaws) has show very little benefit of screening colonoscopies, especially for right-sided cancers. Left sided-cancers are better detected, and sigmoidoscopy is perhaps an adequate screening tool given the meta-analysis. But, that procedure costs about $1500 less than a colonoscopy though it is arguably just as effective.
Perhaps worse for patients, routine colonoscopies can lead to a false sense of security wherein patients ignore signs of colon cancer because they've recently been given a clean bill of health.
Screening scopes are almost certain to be a thing of the past as companies improve and certify DNA testing for colon cancer, as has been done in Germany and other European countries.
Robin,
In general I agree completely that screening is overrated -- my teaching soundbite on it is that screening is the opposite of treatment, since it takes healthy people and makes them sick.
However, I think two of your examples are wrong at least in part.
There's good evidence that the Cochrane Breast Cancer was wrong to discard the trials it claimed had inadequate randomization. See the very detailed analysis by Freedman, Pettiti, and Robins. The authors aren't pro-screening ideologues -- two of them are statisticians and so predisposed not to believe in screening, and Diana Pettiti was co-chair of the panel that, last year, recommended against routine mammography before age 50.
As someone pointed out above, even though ordinary x-ray screening doesn't work for lung cancer, there is now good evidence for CT-scan for lung cancer in smokers and former smokers. I was surprised by this when it came out, but the results are pretty clear.
Re: Prostate cancer testing, you say that "these practices should be ended as soon as possible." In March 2004, at age 54, my primary physician thought my prostate felt "asymmetrical", my urologist concurred, a biopsy came back positive and I had my prostate removed. So far, so good. I understand that many prostate cancers never fully develop, and some are extremely long-developing, but are you saying that I should NOT have had testing done? Are we just supposed to roll the dice and hope for the best? What if I didn't test and I turned out to be too dead to be writing this response? That's not really an acceptable outcome in my opinion.
Huh? Could you describe the reasoning process you use to make that conclusion? I simply don't see it.
Even if a type of cancer screening is shown to improve cancer mortality, or even all-cause mortality, even THAT would not be evidence enough to do it. It would also have to be a better expenditure of resources than the next best use of those resources. So if the benefit is small or the cost huge, the statistically significant mortality benefit may not be enough.
Having had cancer myself, I recall that I spent a lot of time considering moving to cities with outstanding cancer clinics. Ultimately, I found what I needed to survive at home in the Chicago area, but if I had relapses and thus needed a last ditch stem cell transplant, I probably would have gone to a state with a state of the art cancer center, and I probably would have died in that state.
According to a quote (with favorable comment) on Overcoming Bias last year: "The evidence strongly suggests that students learn better when they are not graded and certainly not when they are graded on a curve." Using similar reasoning, we can conclude that being part of a randomized controlled study makes medical care less effective.
The screening tools with the most evidence (pap smear/hpv testing and colonoscopies) are treatment in a way. they remove pre-cancerous lesions.
It'd be considered unethicial to not screen for cervical cancer at this point considering the strong observational data.(ex: http://www.ncbi.nlm.nih.gov...
Almost all of the women who get cervical cancer in the screening era are either from developing countries without screening programs, or women from developed countries who do not regularly getting screened.
It's a shame this wasn't tested in a RCT before it became standard practice, but I doubt you could find a medical researcher or ethicist that would allow women to be in a placebo arm now. I think similar points would be made about colonoscopies. We need further advocation for evaluating screening tools with RCTs before they become standard clinical practice though considering the issues we have with the other cancers (partartically prostate)
Overall, I think you're making an important point but your sweeping generalization that all types of cancer screening is off base and (unfortunately) likely discredits the whole argument in many reader's minds.