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Cancer Screening:
A Updated Primer for
Journalists
Kenny Lin, MD, MPHAssociate Professor of Family Medicine
Associate Deputy Editor,American Family Physician
December 8, 2014
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Disclosures
I receive salary, royalties, or consulting incomefrom the following sources: MedStar Health,American Academy of Family Physicians,
John Wiley and Sons, UpToDate, WebMD,
Business Health Services
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The 2009 Mammography Firestorm
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Science Communication and the
Importance of Context
The U.S. Preventive Services Task Forcerecommends against routine screeningmammography age 40 to 49 years.
Message to clinicians: practice shared decision-making, screen based on patient preferences
Message to the public: a government taskforce prominent in Obamacare legislative
proposals wants to ration mammograms!
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Evaluating cancer screening tests
The ability to detect asymptomatic cancer is anecessary, but not sufficient, quality of a goodscreening test.
Is cure possible in those whom it is necessary?
Is cure necessary in those whom it is possible?
Willet F. Whitmore, Jr., MD
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Potential harms of cancer
screening False positives
psychological harm, physical harm from workup (eg breastor prostate biopsy)
False negatives falsely reassuring, may encourage unhealthy behaviors (eg
continued smoking)
Overdiagnosisdiscovery of pseudodisease thatwill not cause symptoms in the patients lifetime
leads to unnecessary treatment and exposure to harms oftreatment (eg surgical complications)
Opportunity costs may crowd out more effective preventive services
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Journalists can help people understand
and deal with the clash between:
Science
Evidence
Data Recommendations for
entire population
What we can prove
Grasping uncertainty andhelping people applycritical thinking todecision-making issues
Intuition
Emotion
Anecdote Decision-making by an
individual
What we believe, wish, or hope
Promoting false certainty andnon-evidence-based,cheerleading advocacy
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Pitfalls of cancer screening because
it just makes sense
Breast self-exams to detect breast cancer
Chest x-rays to detect lung cancer
Urinalyses to detect bladder cancer
Pelvic exams to detect ovarian cancer
Testicular exams to detect testicular cancer
None of these tests are beneficial, and mostare actually harmful.
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Increasing 5-year survival rates do not
always correlate with fewer deaths
Welch et al. (JAMA, 2000) compared 5-year cancersurvival and mortality statistics in U.S. in 1950-54 and1989-1995
Prostate cancer 5-year survival increased from 43 to 93percent, but mortality ROSEby 10 percent
Melanoma 5-year survival increased from 49 to 88percent, but mortality ROSEby 161 percent
Kidney cancer 5-year survival increased from 34 to 61percent, but mortality ROSEby 37 percent
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Lead Time Bias:
Improving 5-Year Survival Is Not Enough
Death from prostate
cancer
SymptomsAppear
Situation 1: Not Screened
Survival Time
Situation 2
Survival Time
Situation 3
Survival Time
Death
= Lead Time= Life Extended
Found Early
by Screening
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Example: Prostate Cancer
Why is the net benefit of screening so
small?
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Prostate cancer - background
>200,000 new diagnoses each year
2ndleading cause of cancer death in U.S. men
~28,000 deaths in attributed to prostate cancerin U.S. in 2011
1 in 6 men will be diagnosed in their lifetimes,
but only 1 in 33 will die from prostate cancer
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Number of Additional Men Diagnosed and Treated
Since Start of PSA Screening Era
Welch JNCI, 2009
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Woloshin, S. et al. J. Natl. Cancer Inst. 2008 100:845-853; doi:10.1093/jnci/djn124
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The parable of the British WWII
fighter armorers
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The parable of the British WWII
fighter armorers
Too many fighter planes were being shot down
Armor-plating the whole plane would make ittoo heavy to flyso where to put the armor?
The mechanics went out to the airfield andproposed putting armor where the bullet holestended to cluster.
But the statisticians disagreed.
These are the planes that came back. Put the
armor where the bullet holes arent!
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The meaning of this analogy
We care less about finding survivable
cancers with screening tests
We care more about finding cancers that, ifnot detected prior to the onset of
symptoms, are likely to be lethal
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Overdiagnosis: Cancer Is Not All the Same
Death from Other Causes Death from Other Causes
Progre
ssion
ofDisease
Disease Not
Detectable
Patient 1
Detectable
Presymptomatic
Phase
Symptomatic Phase
Remaining Expected Lifetime
Patient 2
Patient 4
Patient 3
Death From Prostate Cancer
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Example: Breast Cancer
The case against reflexive screening,
especially in younger women
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Screening mammography
In randomized controlled trials, biennialscreening mammography lowered breast cancerdeaths by 15 to 25 percent
For simplicitys sake, lets assume that the
correct figure is 20 percent
Why wouldnt recommending routine
mammography be a no-brainer?
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Exaggerating effect size
Absolute vs. Relative Risk
Two ways of saying the same thing
One wayrelative risk reductionmakes
effect size seem larger
Other wayabsolute risk reductionmakeseffect size seem smaller
Most medical journal editors prefer to useabsolute risk reduction
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You must ask: 20% of what?
The of what? is the absolute risk.
When youre only told the relative risk 20% - itcould be risk reduction from 500 in 1000 downto 400 in 1000so 100 benefit.
Or it could be from 5 in 1000 to 4 in 1000.so
only 1 benefits.
You want to know the absolute size of theeffect, not just one relative to another.
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Magnitude of mammographybenefits by age group
Age Trials
included,
n
RR for Breast Cancer
Mortality (95% CrI)
NNI to Prevent 1
Breast Cancer Death
(95% CrI)
39-49 y 8 0.85 (0.75-0.96) 1904 (929-6378)
50-59 y 6 0.86 (0.75-0.99) 1339 (322-7455)
60-69 y 2 0.68 (0.54-0.87) 377 (230-1050)
70-74 y 1 1.12 (073-1.72) Not available
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Weighing Harms and Benefits
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Annual mammography in a group of
2000 women age 40-49 years
Benefits
1 woman will avoid dyingfrom breast cancer
Harms
2-10 women will beoverdiagnosed and receiveunnecessary treatment
1200 women will have atleast one false alarm
140-180 women will have atleast one biopsy for a falsealarm
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Example: Lung Cancer
Why reducing deaths in a randomized
trial doesnt (necessarily) meanscreening should become routine
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National Lung Screening Trial
Randomized study beginning in 2002 Compared low-dose CT with CXR screening in
53,000 current or former heavy smokers (at
least 30 pack-years) age 55-74 By October 2010, 354 lung Ca deaths had
occurred in the CT arm vs. 442 lung Ca deathsin the CXR arm (20% relative risk reduction)
National Cancer Institute announced results ata press conference held Nov. 4, 2010
Published inNew England Journal of MedicineAugust 2011
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Prevention for Profit
Georgetown University CT scans
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Responses from lung cancer screening
advocates
Are you kidding me? The title of your blog postalone is incredibly irresponsible.
As a doctor, I would think your #1 priority would beto try to save lives by doing more than preachingabout smoking.
My lung cancer was caught at [stage] 2B by my GPin an x-ray. Thank God my doctors have morecommon sense than this. The same flawed argument
was made about mammograms. Dr. Lin, I hope none of your patients take your
advice. You are stupid. End of story.
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Absolute benefit of screening
varies by baseline cancer risk
20% reduction in lung cancer deaths is arelativerisk reduction
On average in NLST, needed to screen 320people to prevent one lung cancer death
Highest-risk: 1 in 100 benefit
Lowest-risk: 1 in 5000 benefit
No single accepted risk prediction tool
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Potential harms of screening for
lung cancer
Risk of developing cancer from multiple CTscans
False positives extremely common
Anxiety
Invasive biopsies
Incidental findings
Overdiagnosis and overtreatment
Surgical and perioperative mortality
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Why the NLST results may not be
achieved in clinical practice
Healthy volunteer bias: participants werehealthier and more adherent to screening andfollow-up than the general population
Screenings were performed at high-volumeacademic medical centers with strict protocols
Unclear if benefits & harms similar in
community settings, where a majority ofbiopsies of pulmonary nodules are for benigndisease and lung resection has higher mortality
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AAFP: More evidence is needed
on lung cancer screening
TheAAFP had significant concern withbasing such a far reaching and costlyrecommendation on a single study.
A shared-decision-making discussion betweenthe clinician and patient should occur regardingthe benefits and potential harms of screening for
lung cancer. The long term harms of radiationexposure from necessary follow-up full dose CTscans are unknown.
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Review criteria: Does the storyexplain Whats the total cost?
How often do benefits occur?
How often do harms occur?
How strong is the evidence?
Are there alternative choices?
Is the condition exaggerated?
Is this really a new approach?
Is it available?
Whos promoting this?
Do they have a financial conflict of interest?
69%
66%
65%
61%
57%
Percent
unsatisfactoryafter 1,889
story reviews
7 years
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Acknowledgement
Thanks to HealthNewsReview.org publisher andindependent journalist Gary Schwitzer forgranting permission to use/adapt Slides #8, 26-
27, and 40-42 of this presentation.
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Thanks for your
attention!
Questions?
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