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Lung Cancer Screening

With X-Rays Isn't

BeneficialConway Tan

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+ More than 150,000 Americans aged 55-74

+ 13 years, first 4 years, 77445 were assignedto annual screenings, 77456 were not.

+ About 1200 deaths in both groups

+ Of the 1,696 cancers diagnosed among thosein the X-ray group, about 70% of the cancers

were found during the years after the screeningperiod ended.

Routine X ray screenings do notprevent cancer death

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+ X ray screenings in healthy people withoutsymptoms are "a waste of time," plus they canlead to false-positive results that may lead to

invasive and potentially harmfull tests.

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"We were really hoping chest X-rays might be beneficial,"partly because they are relatively inexpensive - about $60

versus hundreds and sometimes thousands of dollars forCT scans, Dr. Berg said

+ X-ray still useful for symptomatic patients

+ CT provides much detailed images

+ But can also yield false positive results,unlikely to be recommended

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Objective

+ To evaluate the effect on mortality ofscreening for lung cancer using radiographs inthe Prostate, Lung, Colorectal, and Ovarian

(PLCO) Cancer Screening Trial.

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Intervention

+Annual posteroanterior view chest radiographfor 4 years.

+ Control group: No interventions and received

their usual medical care.+ Definition of screen diagnosed case = 9

months from a positive screen, or the

evaluation linked to the positive screen.

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Result - through 13 years

+ Cumulative lung cancer incidence =

-- 20.1 per 10 000 person-years in theintervention group

-- 19.2 per 10 000 person-years in the usualcare group

+ Death observed =-- 1213 in the intervention group

-- 1230 in usual care group

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Lung Cancer Incidence by Year

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Lung Cancer Mortality by Year

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Conclusion

Annual chest radiographic screening for up to 4years did not have an effect on cumulative lungcancer mortality.

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Doubt 1: Smokers out there?

+ Controlled for smokers

-- Straitified by screening center, sex, andage, no eligibility requirement concerning

smoking

-- 45% of the participants reported never

smoking, 10% were smokers and the rest wereprevious smokers when they enrolled in thestudy.

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Doubt 2: Data bias?

+ Diagnose bias:

-- Standardized. Anomaly was noted, thenadvised to seek diagnostic evaluation, result

decided by the patients and their primaryphysicians, not by trial protocol

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Doubt 3: Dead man reporting?

+ Method: Annual study questionnaire mailed, if

no response, repeated mailing and phonecall.

All data supplement by the National Data

(death certificate). Since they are not always

true, all deaths related to cancer (no matter

what kind or possible metastasis) were

reviewed by blinded reviewers.

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Doubt 4: Contamination?

+ No clean cut control: no interventions andreceived their usual medical care.

+ Sojourn time:

-- period in which tumou can beasymptotically detected by chest X-ray = 1-4

years.-- Any cancer diagnosed after the Sojourn

time could not have been affected by thisscreening.

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