Current Cancer Screening Issues

8/10/2019 Current Cancer Screening Issues

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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
http://www.foxnews.com/index.html


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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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