AIMGP Seminar Series January 2004 Joo-Meng Soh Edited by Gloria Rambaldini CANCER SCREENING PART II.
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Transcript of AIMGP Seminar Series January 2004 Joo-Meng Soh Edited by Gloria Rambaldini CANCER SCREENING PART II.
AIMGP Seminar Series
January 2004
Joo-Meng Soh
Edited by Gloria Rambaldini
CANCER SCREENINGPART II
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
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 50 - 69
• 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)
CBE & Mammography For Women Aged 40-49
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 40-
49 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 ACOG - American College of Obstetricians and Gynecologists ACS - American Cancer Society CTFPHC Canadian Task force on Preventive Health Care NIH - National Institutes of Health 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 smallNumber 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
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
Outdated
MANEUVER EFFECTIVENESS LEVEL OF EVIDENCE RECOMMENDATION
Average Risk
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
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