Transcript CANCER SCREENING PART II

CANCER SCREENING
PART II
AIMGP Seminar Series
January 2004
Joo-Meng Soh
Edited by Gloria Rambaldini
OBJECTIVES
• Understand the concept of cancer
screening and the controversies
surrounding this topic
• To learn the Canadian screening
guidelines for Breast and Colorectal
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
Case #1
• While on Team Medicine, you make the
diagnosis of metastatic breast cancer in
your 47 year old female patient
• You think to yourself, “I wonder if she did
Breast Self Examinations? Should she
have received a mammogram? Would
her cancer have been picked up earlier?
Could she have been cured?”
Guidelines Available
Breast Cancer
• Most frequently diagnosed cancer in
women
• In 2001, estimated:
– 19,200 cases diagnosed
– 5,500 deaths
– 2nd leading cause of cancer death in women
(after lung CA)
Canadian Cancer Statistics 2001
http://66.59.133.166/stats/index.html
Breast Cancer Statistics
Risk of being Diagnosed with Breast Cancer
Risk of Dying from Breast Cancer: 1 in 25
Screening Maneuvers
• Breast Self Examination (BSE)
• Clinical Breast Examination (CBE)
• Mammography
Potential Benefits
• Detection of Tumour at earlier stage
• Improved Cosmetic result if found early
• Reassurance if negative screening test
Potential Harms
• Radiation-induced Carcinoma from
mammography
– Est. risk of death from this is 8 per 100,000
women screened annually for 10 years
beginning at age 40
• Unnecessary biopsies
• Psychological stress of call-back
• Possible false reassurance
RCTs for BSE
No reduction in breast cancer mortality or
stage at diagnosis seen in two large scale
on-going RCTs
• Shanghai Trial (n=267 040 women)
– Aged 31-64
– Results after first 5 years of follow-up
• Russian/WHO Trial (n=122 471 women)
– Aged 40-64
– Results after first 5 and 9 years of follow-up
Breast Self-Examination
ON THE OTHER HAND......
• RCTs showed a significant increase in:
– number of physician visits for the evaluation
of benign breast lesions
– breast biopsy rates for benign lesions
Breast Self Examination (BSE)
• 1994 Canadian Task force on Preventive
Health Care made BSE a Class C
recommendation (insufficient evidence to
recommend for or against BSE)
• Due to recent trials, this screening tool
now down-graded to class D (fair
evidence to recommend that BSE be
excluded from the periodic health exam)
CBE & Mammography
For Women Aged 50 - 69
• HIP (Health Insurance Plan) Trial
– RRR of 0.55 in breast ca. mortality over 5 yrs
• Swedish Trials
– RRR of 0.29 in breast ca. mortality over
7-12 years follow-up
• Canadian Trial comparing mammography
over CBE
– RRR of 0.03 (NS) at 7 years follow-up
CBE & Mammography
For Women Aged 50 - 69
Breast Cancer Screening with both CBE
and mammography should be done for
women aged 50-69 annually (Grade A
Recommendation)
CBE & Mammography
For Women Aged 40 - 49
• CONFLICTING RESULTS!!!
• Only one RCT designed specifically for
women aged 40-49 did not have adequate
power to exclude a clinically sig. benefit
• Other RCT results are from post hoc
subgroup analyses
CBE & Mammography
For Women Aged 40-49
• RRR of 18%-45% in breast cancer
mortality at 10 years shown in 2 trials and
1 meta-analysis
• No benefit was shown in 6 other trials
• Recommendations:
– Evidence does not support the use or
exclusion of mammography for the periodic
health exam in women aged 40-49 (Grade C)
Back to the Case
• “I wonder if she did BSEs”
– Not currently recommended
• “Should she have received a mammogram”
– Unclear at this point in time; Women aged 4049 should be informed of the risks and benefits
of screening mammography and then assisted
in making a decision”
• “Would her cancer have been picked up
earlier? Could she have been cured?”
– Possibly....
OTHER Guidelines
 AAFP - American Academy of Family Physicians
 ACS - American Cancer Society
 NIH - National Institutes of Health
 ACOG - American College of Obstetricians and Gynecologists
 CTFPHC Canadian Task force on Preventive Health Care
 USPSTF - U.S. Preventive Services Task Force
Case #2
• During your GI rotation you consult on a 54
year old male with newly diagnosed
metastatic colon cancer
• Your team debates whether screening
could have detected the cancer earlier?
• Although the GI fellow swears by
colonoscopies you wonder ‘what about all
the hype regarding fecal occult testing vs
sigmoidscopes vs barium enemas vs virtual
c-scopes vs…”
Guidelines Available
COLORECTAL CANCER
• Third most common cancer in Canada
• In 2001, Estimated
– New cases: 17,200
– Deaths:
6,400
Canadian Cancer Statistics 2001
http://66.59.133.166/stats/index.html
Screening Tools
•
•
•
•
Fecal Occult Blood Testing
Sigmoidoscopy
Barium Enema
Colonoscopy
Fecal Occult Blood (FOB)
• Rationale – detect occult blood from
cancers or large polyps
• 3 consecutive stool samples at home
• Evidence from 4 large-scale RCTs
• Overall Sensitivity  25 - 50%
• False positive rate  10%
Overall benefits are statistically sig. but small
Number needed to screen for 10 years to avert
one death from colorectal cancer = 1173
Sigmoidoscopy
• May reduce the risk of death from
Colorectal cancer (3 case control studies)
• 3 RCTs suggest it may be superior in
detecting adenomas and possibly cancer
than FOBT (but no mortality data)
• Potential Harms:
–Bowel perforation in 1.4 per 10,000 exams
Colonoscopy
• Currently no direct evidence on mortality
benefit from colonoscopy as a screening
maneuver
• Potential Harms:
–Bowel perforation in 10 per 10,000 exams
Comparison of all Three
• Recent NEJM article: Aug. 23, 2001
“One-Time Screening for Colorectal Cancer
with Combined FOBT and Examination of the
Distal Colon”, Lieberman D et al
• n = 2885 patients
• All patients provided stool for FOBT, then
underwent Colonoscopy (“sigmoidoscopy”
was defined as examination of the rectum
and sigmoid colon during colonoscopy)
Comparison of all Three
• Only 23.9% of patients with advanced
neoplasia had a positive FOBT
• Sigmoidoscopy identified only 70.3% of
all subjects with advanced neoplasia
• Combined FOBT and sigmoidoscopy
identified only 75.8% of subjects with
advanced neoplasia
In other words, combined FOBT and
sigmoidoscopy would have missed 25%
of the colorectal cancers
Canadian Recommendations
• Good evidence to include annual or biennial
FOBT (Grade A Recommendation)
• Fair evidence to include Flexible
Sigmoidoscopy (Grade B Recommendation)
• Insufficient evidence to make
recommendations about whether only one or
both tests should be performed (Grade C)
• Insufficient evidence to include or exclude
colonoscopy as initial screening test Grade
C)
Colorectal Cancer Screening – Recommendations from the Canadian
Task force on Preventive Health Care CMAJ 2001; 165(2): 206 - 208
Other Guidelines
Outdated
 AAFP - American Academy of Family Physicians
 ACOG - American College of Obstetricians and Gynecologists
 ACS - American Cancer Society
 AMA - American Medical Association
 AGA - American Gastroenterological Association
 CTFPHC - Canadian Task Force on Preventive Health Care
 USPSTF - U.S. Preventive Services Task Force
MANEUVER
EFFECTIVENESS
LEVEL OF EVIDENCE
RECOMMENDATION
Multiphase screening with
the Hemoccult test for
average risk adults > age
50
Relative risk of CRC*
death with screening with
Hemoccult testing is 0.84
(95% CI 0.77-0.93) in
those who are compliant
NNT=1173 over 10 yrs
Randomized controlled
trials and meta-analyses
Good evidence to include
screening with annual or
biennial Hemoccult test in
the periodic health
examination (PHE) of
patients >50
Sigmoidoscopy for
average risk adults > age
50
Patients with rectal
cancers were less likely to
have had a sigmoidoscopy
in the previous 10 yrs
Case-control studies, case
series
Fair evidence to include
screening with flexible
sigmoidoscopy in the PHE
of patients > 50
Hemoccult/sigmoidoscopy
in combination for average
risk adults > age 50
Some evidence that the
addition of flexible
sigmoidoscopy increases
the detection rate of
adenomas and colorectal
cancer. Nor mortality data
RCT
Insufficient evidence to
make recommendations
about whether only 1 or
both of FOBT and
sigmoidoscopy should be
performed
Colonoscopy
Indirect evidence from
RCT showing decreased
colorectal cancer mortality
RCT
Insufficient evidence to
include or exclude
colonoscopy from PHE
Average Risk
Back to the Case
• Screening can result in the reduction in CRC
related mortality
• Recommendations thus far include routine
FOBT and sigmoidoscopy
• Routine colonoscopy is not supported by
good evidence at present
• Like all screening tests…patient counseling
will guide you and the patient
Other References
• Cancer Screening Guidelines,
American Family Physician 2001, 63(6):1101-1112
– Summarizes in table format the guidelines published by
multiple organizations
• Preventive Health Care, 2001 update: screening
mammography among women aged 40-49 years at
average risk of breast cancer,
CMAJ 2001; 164(4): 469-76
• Preventive Health Care, 20001 update: Should women
be routinely taught BSE to screen for breast cancer,
CMAJ 2001; 164(13): 1837-46