Cervical Cancer: Screening and Prevention
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Transcript of Cervical Cancer: Screening and Prevention
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Cervical Cancer: Screening and Prevention
Pacific Regional Comprehensive Cancer Control ProgramUniversity of Hawaii Department of Family Medicine and Community HealthJune 9, 2008
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Intended Audience
Physicians Public health nurses performing cervical
cancer screening
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Learning Objectives
Upon conclusion of this educational activity, the participant will be able to: Discuss the role of human papillomavirus (HPV)
infection and the development of cervical cancer Describe different screening methods for the
prevention of cervical cancer Discuss the role of HPV vaccination in preventing
cervical cancer
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Why do we care about cervical cancer? 2nd most common cancer worldwide 500,000 cases worldwide 275,000 deaths More than 80 percent of the cases are in the
developing world Lifetime risk of developing cervical cancer in
the developing world is 2-4 percent
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Cervical cancer strikes at a young age Cervical cancer strikes between ages 35 to
55 By comparison:
Lung cancer average age is 69 90 percent of colon cancers occur after the age of
50 Breast cancer average age is 62 Prostate cancer average age is 68-70
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More advanced disease
More likely to be advanced disease at time of detection
Cervical cancers are diagnosed at younger ages and more advanced stages in Micronesian, Marshallese, and American Samoan women living in the U.S. Associated Pacific Islands (USAPI) than in U.S. white women
50 percent mortality rate
Treatment options often unavailable
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Risk Factors
HPV infection Lack of screening Tobacco use Early onset of sexual activity Multiple sexual partners over time Multiparity Long-term use of oral contraceptives Immunosuppresion History of sexually transmitted infection (STI) Circumcision has protective effect for transmission
of HPV
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Signs and Symptoms
Abnormal vaginal bleeding Postcoital bleeding Vaginal discharge Pelvic or lower back pain Hematuria Hematochezia
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Human Papillomavirus (HPV)
HPV infects the epithelium of skin and mucous membranes
When a persistent HPV infection occurs at a transformation zone between different kinds of epithelium, cancer can develop
These zones exist in the cervix, anus, and oropharynx
HPV infection necessary to cause cervical cancer
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Cervical Transformation Zone
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HPV
118 types classified 30 types associated with cervical cancer, 15
of which cause almost all cancers Types 16 and 18:
Cause 70 percent of all cervical cancers Cause 50 percent of all CIN3
Types 6 and 11: Cause 90 percent of all genital warts
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HPV infections
Estimated that 6.2 million people in the U.S. are newly infected with HPV each year
20-30 percent of women have infection with multiple strains
So why are there so many people infected, but much fewer cervical cancers?
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HPV and the immune response Most cervical HPV infections are cleared or
suppressed in 1-2 years Clearance occurs through:
Desquamation of epithelial cells Cell-mediated immunity Neutralizing antibodies
Smoking Average time is 12 months
75-90 percent within 1 year This includes those with cytologic abnormalities
Data from older women and HIV patients suggests that many infections are suppressed rather than cleared
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Cervical Cancer Development Infection
Cervical transformation zone Persistence
Virus not cleared Precancer
Normal epithelium replaced by undifferentiated cells
Invasion 20-30 percent of precancers invade over 5-10
years
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Types of Cervical Cancer
Squamous cell - 70 percent Adenocarcinoma - 25 percent Adenosquamous - 3 to 5 percent
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Preventing Cervical Cancer
Screening for precancer or high-risk HPV Looks for evidence of infection by analyzing cells,
cervical appearance, or DNA Affects persistence and precancer stage
Primary prevention through vaccination Vaccine given before infection Prevent persistence stage
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What is cancer screening?
Aimed at detected cancer early, when treatment may be easier, more effective and available on-island
Testing for early forms of disease before symptoms occur
Need a reliable early detection test Tests a large number of healthy people to
identify those with a high probability of having clinically unrecognized cancer or precancerous lesions.
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Screening Techniques
Papanicolaou (Pap) smear (cytology-based)
Visual inspection with Acetic Acid (VIA) or with Lugol’s Iodine (VILI)
HPV DNA detection
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Barriers to screening
Cultural Unaware of importance Lack of resources
Equipment and supplies Laboratory Funding Trained professionals Female health professionals
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Pap smears
Cells taken from transformation zone and endocervical canal are analyzed for histologic changes associated with precancer
Conventional: samples obtained by brush and spatula are plated on a microscope slide
Liquid-based: samples obtained by brush are placed in liquid medium and spun in lab to plate only a monolayer Can also test for gonorrhea, chlamydia and HPV
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Pap smears
50-60 million Pap smears are done in the U.S. each year
3.5 million of these are classified as abnormal 2.5 million of these women undergo
colposcopy
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Pap smear results
Bethesda Classification WHO classification
Atypical squamous cells (ASC)
Undetermined significance (ASCUS)
Cannot exclude high-grade SIL
Squamous atypia
LSIL (low-grade squamous intraepithelial lesions)
Cervical intraepithelial neoplasia (CIN) 1
HSIL (high-grade squamous intraepithelial lesions)
CIN 2, CIN 3, carcinoma in situ
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Pap smear results
Only one-third of women with HPV by DNA testing have pathology seen on Pap.
CIN 2 can be produced by types of HPV that are not carcinogenic. Equivocal
CIN 1 is very insensitive Does not predict a higher risk of CIN 3 than a
negative biopsy
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Pap smears
Sensitivity: 60 percent Specificity: 95 percent
Review: Sensitivity-probability that a person with the disease will
test positive. It equals the number of people with positive tests over the number of people with the disease
Specificity-probability that a person without the disease will test negative. It equals the number of people with a negative test over the number or people without disease
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Pap smears
Pros: Have dramatically
reduced the incidence of cervical cancer in many developed countries
Most specific
Cons: Requires laboratory
infrastructure Requires highly-trained
cytotechnologists Extensive workup of
abnormal results Treatment occurs later Least sensitive
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http://screening.iarc.fr/atlaspitfall.php
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Direct visual inspection
Apply 3-5 percent acetic acid (VIA) or Lugol’s iodine (VILI) to cervix
Inspect with naked eye or magnifying device to look for changes associated with precancer
Developed in 1930s, before cytology-based screening
Proven effective in reducing cervical cancer Many ongoing international trials and training
http://screening.iarc.fr/study_major.php?lang=1
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IARC Clinical Reference Chart for VIA
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Direct visual inspection (DVI)(Visual Inspection with Acetic Acid [VIA]) Sensitivity: 68 percent Specificity: 85 percent
Sensitivity varies by provider and by standard applied for treatment (65-96 percent)
Likely lower sensitivity outside of research institutions
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Direct visualization
Pros: Screen-and-treat at same
visit Low cost Does not require close
follow-up (rescreen in 1 year if initial positive screen & treat)
Do not need lab infrastructure
Cons: Sensitivity varies by
person Squamocolumnar
junction (SCJ) moves inward with increased age
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HPV DNA testing
Samples collected from cervix are tested for presence of high-risk strains of HPV
Can also be collected by the patient
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HPV DNA testing
Sensitivity: 84 percent Specificity: 88 percent
Sensitivity for patient-collected specimen: 67 percent
Specificity for patient-collected specimen: 83 percent
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HPV DNA testing
Pros: Detects this high risk
strains of HPV which cause almost all cervical cancers
Can be self-collected Greatest reproducibility Most sensitive
Cons: More costly than DVI Most likely requires 2
visits
Rapid, low-cost HPV DNA test being developed by Program for Appropriate Technology in Health (PATH)
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Screening Comparison
Most effective: HPV DNA testing 27 percent cancer risk reduction
Most cost-effective: DVI Saves money compared to not screening 26 percent cancer risk reduction
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Screening Guidelines
United States Preventive Services Task Force (USPSTF) Screen women who have been sexually active and have a
cervix Start screening at age 21, or 3 years after the onset of
sexual activity (whichever comes first) Stop screening at age 65, and women who have had a
hysterectomy for benign disease Screen at least every 3 years Insufficient evidence to recommend for or against liquid-
based cytology, computerized rescreening, or HPV DNA testing as primary screening modality
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Primary Prevention
HPV vaccine Two currently available:
Gardasil HPV 6, 11, 16, 18 Approved in U.S. and several other countries
Cervarix HPV 16, 18 Approved in Australia
Others in development More than 4 types
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HPV Vaccines
Virus-like particle (VLP) vaccine Inject recombinant L1 protein as non-
infectious capsid No genetic material Antibody response 20-50 times as high as
that induced by natural infection
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HPV Vaccines
Data currently shows vaccine effect for more than 5 years Studies being done to demonstrate 10 year
efficacy Efficacy 95 percent in those not receiving all
doses of vaccine Generally safe and well-tolerated
Fever and pain at injection site most common complaint
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HPV Vaccines
Do not treat current infections
Only prevent future infections Limits usefulness in older populations who are
already sexually active
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Gardasil
3 doses, at 0, 1, and 6 months Cost roughly $120 per dose Recommended ages: 9-26
Advisory Committee on Immunization Practice and American College of Obstetricians and Gynecologists
Note: If women 15 to 26 are to be immunized, program must consider what % of these woman are already infected with HPV 16, 18 (vaccine not as effective in these women). If a significant portion— will need to think through strategy.
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Questions about HPV vaccines How well does it work with fewer than three doses? How long is the duration of protection? Will boosters be needed? Are they effective in men? What about the other oncogenic HPV types that
aren’t covered? Do we revaccinate the covered cohorts when new
vaccines come out that protect for more than 4 HPV types?
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HPV Vaccines
Pros: Nearly 100 percent protection
against precancer and cancer caused by most common high-risk strains
Well-tolerated (although painful shots)
Can be integrated as part of comprehensive cervical cancer screening program
Cons: Effect not seen for 20-30 years Cost of program
implementation Sustainability in resource
limited setting Questions still remain Only targets strains causing 70
percent of cancers Does not protect women
already infected Still need good screening
program Potential of creating
expectation for health services and population that this is the “answer” for cervical cancer
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Screening and Prevention
0
20
40
60
80
100
15 25 35 45 55
Age
Eff
ec
tiv
en
es
sVaccinationScreening
Infection Persistence Precancer Invasion
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Summary
HPV infections in the transformation zone of the cervix lead to cervical cancer
Cervical cancer risk factors include lack of screening, smoking, and history of STIs
4 steps to cervical cancer: infection, persistence, precancer, and invasion
Screening for cervical cancer via cytology, DVI, or DNA testing can prevent cervical cancer
Vaccinating against high-risk HPV can prevent cervical cancer
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References
Burd E. Human Papillomavirus Detection and Utility of Testing. Clinical Microbiology Newsletter. 2007; 29,21: 159-167.
Denny L, Kuhn L, De Souza M, Pollack A, Dupree W, Wright T. Screen-and-Treat Approaches for Cervical Cancer Prevention in Low-Resource Settings. Journal of the American Medical Association. 2005; 294,17: 2173-2181.
Frazer I. HPV vaccines and the prevention of cervical cancer. Update on Cancer Theraputics. 2008; 3: 43-48.
Goldie S, Kuhn L, Denny L, Pollack A, Wright T. Journal of the American Medical Association. 2001; 285, 24: 3107-3115.
http://www.medscape.com (Medscape) http://www.rho.org (RHO Cervical Cancer) http://www.uptodate.com (UptoDate) Schiffman M, Castle P, Jeronimo J, Rodriquez A, Wacholder S. Human
papillomavirus and cervical cancer. Lancet. 2007; 370: 890-907. Wright T. Cervical Cancer Screening Using Visualization Techniques.
Journal of the National Cancer Institute Monographs. 2003; 31: 66-71.
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Additional Resources
http://screening.iarc.fr/index.php
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Post-testQuestion T F
1. Most HPV infections lead to precancer.
2. The squamocolumnar junction moves into the endocervix with advancing age.
3. Lack of screening is a risk factor for cervical cancer.
4. The most cost-effective screening measure is Pap smears.
5. The USPSTF recommends screening at least by age 21.
6. HPV vaccines do not treat existing infections.
7. DVI always requires multiple visits.
8. Most cervical cancers are caused by HPV types 16 and 18.
9. Vaginal bleeding can be a symptom of cervical cancer.
10. HPV vaccines should be targeted at 25-35 year-olds.