Transcript CANCER SCREENING PART I

CANCER SCREENING
PART I
AIMGP Seminar Series
January, 2004
Joo-Meng Soh
Edited by Gloria Rambaldini
CASE #1
Your father has just turned 50 years old
and his family doctor is recommending
prostate cancer screening tests.
He has been reading the newspapers and
came across the following article:
Toronto Star, Dec. 31, 2001
CASE #1
He asks you if he should be screened
and what tests he should undergo...
You tell him:
a) No ... the health care system can’t afford it
b) Yes – go for a Digital Rectal Exam
c) Yes – go for a PSA test
d) Yes – go for a DRE and a PSA
e) Don’t know – I haven’t been through AIMGP
Cancer Screening Guidelines Part I yet....
OBJECTIVES
• Understand the concept of cancer
screening and the controversies
surrounding this topic
• To learn the Canadian screening
guidelines for Prostate and Cervical
cancer
• To be aware of other cancer screening
guidelines available
Principles of Cancer Screening
• Screening of asymptomatic individuals to
detect early cancers which may be
curable
• Use of diagnostic tests of high sensitivity
• Diagnostic tests are suitable to the patient
• Natural history of disease can be
changed by intervention
• Proposed early treatment should be
beneficial and not harmful to the patient
Guidelines Available
Website: http://www.ctfphc.org
Guidelines Available
http://www.hc-sc.gc.ca/hppb/healthcare/pubs/clinical_preventive/
Prostate Cancer
• 2nd most frequent cause of cancerrelated deaths among males
• Rapid rise in incidence over age 60
• Lifetime risk of developing prostate
cancer=16 %; risk of dying 3%
• Many cases not clinically evident:
– at autopsy prostate CA in one-third of
men<80, two-thirds men >80
• Prostate CA grows slowly: most
men die of other causes
Prostate Cancer
Canadian Statistics:
• Estimated New cases for 2001: 17 800
• Estimated Deaths for 2001: 4300
Canadian Cancer Statistics 2001 Website:
http://66.59.133.166/stats/maine.htm
Options for Screening
• Digital Rectal Examination
• Prostate-Specific Antigen (PSA)
• Trans-Rectal UltraSound (TRUS)
– not recommended as a screening tool 
primary use is to guide biopsies
Digital Rectal Examination
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Sensitivity Poor
40-50% of cancers are out of reach
Inter-rater reliability low-moderate
PPV 15-30%, NPV even lower
NOTE:
Since Gold Standard Test is prostatectomy
or extensive biopsy, Sens. & Spec. cannot be
accurately determined  Positive and Negative
Predictive Values are used instead
Prostate Specific Antigen
• Produced by epithelial cells of prostate
• Levels > 4.0 ng/mL “suspicious”
• Physicians' Health Study (22,000
men with long-term follow-up)
– sensitivity of a single baseline PSA
>4.0 ng/mL approximately 73% for
any prostate cancer
– 87% for aggressive cancers
– Canadian data suggests high false
positive rates
Prostate Specific Antigen
• Positive Predictive Value:
– If PSA 4-10: 22%
– If PSA >10: 40-60%
• Conditions which increase PSA levels
– BPH, DRE
– TRUS, Biopsy
– Prostatic infection, recent ejaculation
Prostate Specific Antigen
• As PSA levels increase:
– Odds of cancer increase
– Odds of extra-capsular or metastatic
disease increase
– Odds of “cure” decrease if it is cancer
PSA - Pros
• Detect cancer early, while still curable
PSA - Cons
• No evidence for a
reduction in morbidity
or mortality
• Positive test may
result in unnecessary
tests and treatments
PSA – Cons
• Treatment of early stage cancer may
have no impact on overall survival
• Even combined with DRE, PPV not
substantially higher (20%)
• Possible harms with treatment
(prostatectomy or radiation therapy):
– impotence, urinary incontinence,
peri-operative morbidity/mortality
Prostate Screening Guidelines
Variety of Recommendations exist:
 AAFP
American Academy of Family Physicians
 ACP-ASIM American College of Physicians-American Society of
Internal Medicine
 ACS
American Cancer Society
 AUA
American Urological Association
 AMA
American Medical Association
 CTFPHC Canadian Task Force on Preventive Health Care
 USPSTF U.S. Preventive Services Task Force
Recommendations
• Canadian Task Force on Preventative
Health Care:
“Based on the absence of evidence for
effectiveness of therapy and the substantial
risk of adverse effects of associated with such
therapy and the poor predictive value of
screening tests, there is at present insufficient
evidence to support wide-spread initiatives for
the early detection of prostate cancer.”
Recommendations
ACP-ASIM gives a pragmatic compromise:
“Physicians should describe potential benefits
and known harms of screening, diagnosis,
and treatment; listen to the patient’s
concerns, then individualize the decision to
screen”
Counseling Patients
• Prostate Cancer is an important health
problem
• Benefits of Screening are unproven
• DRE & PSA can have false positives
and false negatives
• Probability of further invasive evaluation
is high (around 15%)
Counseling Patients
• If a tumour is found, aggressive therapy
(along with its risks/complications) is
necessary to realize any benefit
• Early detection may save lives and
avert future cancer-related illness
Counseling Patients
• Ministry of Health and Longterm Care
provides information for patients:
• Available through ICES Website:
http://www.ices.on.ca/
Back to the Case
• Review the data
• Discuss the options with the family
doctor
• Then make an informed decision on
whether or not to undergo screening
CASE #2
62 y.o. widowed female with two
healthy children
She says, “I’m 62 years old now and no
longer sexually active. My last two PAP
tests were negative.” She asks ”Do I
really need another one? Will this ever
end???”
CASE #2
You tell her:
a) No – you are too old for it now
b) No – because your last two were
negative
c) Yes – every year
d) Yes – every 3 years
e) I don’t know yet.....but I’ll tell you in 5
minutes (after the end of this seminar)
Guidelines Available
Cervical Cancer
• 11th most common cancer among
women in Canada
• Canada, 1993:
– 1300 women developed cervical cancer
– 400 women died of the disease
Canadian Statistics:
• Estimated New cases (2001): 1450
• Estimated Deaths (2001): 420
Cervical Cancer
• Risk Factors
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early age at first sexual intercourse (<17y/o)
multiple sexual partners (>2)
smoking
low socioeconomic status
HPV Infection (Types 16, 18, 31, 39, 45, 56, 58,
59, 68)
Hx STDs
Hx other lower genital tract neoplasia
Radiation
Immunosuppression
OCPs
Cervical Cancer Screening
• Papanicolaou Smear Test
• High False Neg. Rate: up to 25%
– Sampling error (failure of MD to obtain
malignant cells from the cervix; failure to
take samples from the squamo-columnar
junction)
– Lab Error
• Note: testing for HPV not currently
recommended
The Evidence
• No RCT’s- due to the widespread use of
this screening test
• Only Cohort and Case-control studies
provide evidence for a reduction in the
incidence of invasive disease
• Optimal frequency of screening is less
known
Cervical Cancer Screening Guidelines
 AAFP:
American Academy of Family Physicians
 ACOG: American College of Obstetricians and Gynecologists
 ACS:
American Cancer Society
 AMA:
American Medical Association
 CTFPHC:Canadian Task force on Preventive Health Care
 USPSTF: U.S. Preventive Services Task Force
Canadian Guidelines
Addendum
• Consider screening more frequently in
high risk women (due to the high FN
rate and the variable rate of progression
of disease)
• The largest group of women at risk of
dying from cervical cancer are those
who have never been screened before
BACK TO THE CASE
• Continue screening every 3 years until
the age of 69
• The Pap tests will eventually end....
Principles of Cancer Screening
• Screening of asymptomatic individuals to
detect early cancers which may be
curable
• Use of diagnostic tests of high sensitivity
• Diagnostic tests are suitable to the patient
• Natural history of disease can be
changed by intervention
• Proposed early treatment should be
beneficial and not harmful to the patient