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Principles of Screening . William C. Black, M.D. Dartmouth-Hitchcock Medical Center William.Black@Hitchcock.org www.dhmc.org/goto/chest-imaging. Definition. Screening can be defined as the systematic testing of individuals who are asymptomatic with respect to

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principles of screening
Principles of Screening

William C. Black, M.D.

Dartmouth-Hitchcock Medical Center

William.Black@Hitchcock.org

www.dhmc.org/goto/chest-imaging

definition
Definition

Screening can be defined as the systematic testing

of individuals who are asymptomatic with respect to

some target disease. The purpose of screening is to

prevent, interrupt, or delay the development of

advanced disease in the subset with a pre-clinical

form of the target disease through early detection

and treatment.

Hillman et al. JACR 2004;1(11):861-864

screening vs diagnosis
Screening vs Diagnosis

Non-patients

Patients

Asymptomatic

Symptomatic

Test non-diagnostic

Test diagnostic

Low prevalence

High prevalence

timeline of disease

PRECLINICAL

CLINICAL

DPCP

Onset ofDisease

Detectableby Test

Signs orSymptoms

Death fromDisease orOther causes

Timeline of Disease
critical point
Critical Point

The point in the natural history of disease

before which therapy is more effective.

screening effective

DPCP

Critical Point

Screening Effective

Onset ofDisease

Detectableby Test

Signs orSymptoms

Death fromDisease orOther causes

screening ineffective

Critical Point

Screening Ineffective

DPCP

Onset ofDisease

Detectableby Test

Signs orSymptoms

Death fromDisease orOther causes

screening unnecessary

Critical Point

Screening Unnecessary

DPCP

Onset ofDisease

Detectableby Test

Signs orSymptoms

Death fromDisease orOther causes

survival vs stage
Survival vs Stage

Mountain CF. Chest 1986;89(suppl):225-233.

mayo clinic project
Mayo Clinic Project

1 91 prevalent cases and 1631 others excluded before randomization

2 based on cumulative lung cancer mortality at eleven year

mayo clinic project11
Mayo Clinic Project

1 91 prevalent cases and 1631 others excluded before randomization

2 based on cumulative lung cancer mortality at eleven year

knox pa
Knox PA
  • Hamartoma
screen detected cases elcap
Screen Detected Cases ELCAP

Henschke et al. Lancet 1999;354(9173):99-105.

screen detected cases elcap15
Screen Detected Cases ELCAP

Henschke et al. Lancet 1999;354(9173):99-105.

Estimated five-year survival 80% vs 13% in SEER

biases of early detection
Biases of Early Detection
  • Lead time bias
  • Length bias
  • Overdiagnosis bias
lead time bias

Signs or symptoms

Death fromDisease

WITHOUT TEST

SURVIVAL

WITH TEST

Positive test

SURVIVAL

LEADTIME

Lead Time Bias
length bias
Length Bias

TEST

  • Rapidly progressive

Slowly progressive

TIME

length bias19
Length Bias

TEST

  • Rapidly progressive

Slowly progressive

TIME

length bias20
Length Bias

TEST

  • Rapidly progressive

Slowly progressive

TIME

tumor histology elcap
Tumor Histology ELCAP

25 Prevalent Cases

  • Adenocarcinoma (18)
  • Bronchioloalveolar carcinoma (3)
  • Mixed squamous adenocarcinoma (3)
  • Squamous cell carcinoma (1)
  • Atypical carcinoid (1)

Henschke et al. Lancet 1999;354(9173):99-105.

overdiagnosis
Overdiagnosis

The diagnosis of a condition that

would not have become clinically

significant had it not been detected.

growth rate of lung cancer
Growth Rate of Lung Cancer

Winer-Muram. Radiology 2002;223(3):798-805.

  • Median DT 181 days
  • 22% DT >= 465 days
  • 94% >= 1 yr grow 0.5-3.0 cm
lung ca screening in japan
Lung Ca Screening in Japan

Sone et al. Br J Cancer 2001; 84(1): 25-32.

effects of overdiagnosis
Effects of Overdiagnosis
  • Falsely increases sensitivity of test
  • Falsely increases PPV of test
  • Falsely increases incidence
  • Falsely improves stage distribution
  • Falsely improves case survival
  • Does not decrease pop mortality
population based mortality
Population-based Mortality

Deaths from disease

Person-years of observation

observational studies
Observational Studies
  • Correlation
  • Case-control
  • Cohort
selection bias
Selection Bias

If higher, then bias against screening

If lower, then bias in favor of screening

Those screened at different risk than those not screened.

randomized clinical trial
Randomized Clinical Trial

To ensure that observed differences in

outcome depend only on the interven-

tions under investigation and not on

other factors that affect outcome.

screening rct

Assess Endpoints

Assess Endpoints

Enroll screen

eligible subjects

Screening RCT

Randomize

Screen Arm

Control Arm

benefits from screening
Benefits from Screening
  • ¯ Anxiety about dz (TN)
  • ¯ Morb & mort from dz
  • ¯ Morb & mort from rx
    • lobectomy vs pneumonectomy
harms from screening
Harms from Screening
  • Direct effect of test (radiation)
  • ­ Anxiety about dz (FP)
  • ­ Morb & mort from work-up
  • ­ Overdiagnosis
patient population
Patient Population
  • High risk for preclinical disease
  • No clinical signs or symp of disease
  • Willing and able to undergo screening or not
  • Willing and able to undergo workup and rx
  • Willing and able to undergo follow-up
endpoints
Endpoints
  • Deaths from target disease
  • Deaths from any cause
  • Stage of target disease at dx
  • Adverse events
  • Quality of life
  • Resource utilization
sample size determination
Sample Size Determination
  • Death rate from disease
  • Duration of follow-up
  • Effectiveness of screening
  • Power and significance level
  • Compliance in each arm
sample size
Sample Size

a = 0.05 (one-sided), b = 0.20

all cause mortality
All Cause Mortality
  • Not affected by COD misclassification
  • Puts screening in perspective
  • Insensitive measure of efficacy
generalizability
Generalizability
  • Participants
  • Screening tests and radiologists
  • Treatment and supportive care
rct limitations
RCT Limitations
  • Compliance
  • Statistical power
  • Ascertainment Bias
  • Generalizability
cancer screening outcomes and values
Cancer Screening Outcomes and Values

True positive, effective

Major benefit. Death postponed,

morbidity decreased

True positive, ineffective

Knowledge vs longer dx & rx

True negative

Reassurance

False positive

Harm. Work up

False negative

Possibly delayed dx

Overdiagnosis

Moderate to major harm. False

labeling and rx

summary
Summary
  • Diseases are dynamic processes
  • The evaluation of screening is difficult
  • Survival statistics are inappropriate and biased
  • RCT is most valid design, but has limitations.
references
References

1. Bach PB, Niewoehner DE, Black WC. Screening for lung cancer: the guidelines. Chest 2003;123(1 Suppl):83S-88S.

2. Black WC. Overdiagnosis: An underrecognized cause of confusion and harm in cancer screening. J Natl Cancer Inst 2000;92(16):1280-2.

3. Black WC, Haggstrom DA, Welch HG. All-cause mortality in randomized trials of cancer screening. J Natl Cancer Inst 2002;94(3):167-73.

4. Black WC, Welch HG. Advances in diagnostic imaging and overestimations of disease prevalence and the benefits of therapy. New England Journal of Medicine 1993;328(17):1237-43.

5. Black WC, Welch HG. Screening for disease. AJR. American Journal of Roentgenology 1997;168(1):3-11.

6. Fontana RS, Sanderson DR, Woolner LB, Taylor WF, Miller WE, Muhn JR, et al. Screening for lung cancer: a critique of the Mayo Lung Project. Cancer 1991;67(suppl):1155-1164.

7. Henschke CI, McCauley DI, Yankelevitz DF, Naidich DP, McGuinness G, Miettinen OS, et al. Early Lung Cancer Action Project: overall design and findings from baseline screening [see comments]. Lancet 1999;354(9173):99-105.

8. Hillman BJ, Black WC, D'Orsi C, Hauser B, Smith R. The Appropriateness of Employing Imaging Screening Technologies -

Report of the Methods Committee of the ACR Task Force on Screening Technologies. JACR 2004;1(11):861-864.

9. Morrison AS. The natural history of disease in relation to measures of disease frequency. In: Screening in chronic disease. 2nd ed. New York: Oxford University Press; 1992. p. 21-42.

10. Mountain CF. A new international staging system for lung cancer. Chest 1986;89(suppl):225S-233.

11. Obuchowski NA, Graham RJ, Baker ME, Powell KA. Ten criteria for effective screening: their application to multislice CT screening for pulmonary and colorectal cancers. AJR Am J Roentgenol 2001;176(6):1357-62.

12. Sone S, Li F, Yang ZG, Honda T, Maruyama Y, Takashima S, et al. Results of three-year mass screening programme for lung cancer using mobile low-dose spiral computed tomography scanner. Br J Cancer 2001;84(1):25-32.

13. Welch HG, Schwartz LM, Woloshin S. Are increasing 5-year survival rates evidence of success against cancer? JAMA 2000;283(22):2975-8.

14. Winer-Muram HT, Jennings SG, Tarver RD, Aisen AM, Tann M, Conces DJ, et al. Volumetric growth rate of stage I lung cancer prior to treatment: serial CT scanning. Radiology 2002;223(3):798-805.

disclaimer
Disclaimer

This web site and contents is provided for informational and educational purposes only and is not intended as medical advice nor is it intended to create any physician-patient relationship. Please remember that this information should not substitute for a visit or a consultation with a health care provider. The views or opinions expressed in the resources provided do not necessarily reflect those of Dartmouth-Hitchcock Medical Center or the Radiological Society of North America.

financial disclosure
Financial Disclosure

I do not have nor have I had during the previous 12 months a relationship with a company or organization whose products or services are directly related to the subject matter of this presentation.

William C. Black, M.D.