Download Antenatal Care as Screening

Screening for Cervical Cancer
Max Brinsmead MB BS PhD
May 2015
Cervical Cytology
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As a screening test for Ca Cx this test has only ~75%
sensitivity
Better at detecting Cervical Intraepithelial Ca (CIN)
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Must sample the squamocolumnar junction
More significant if +ve in a high risk individual
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but then specificity is a problem
Older
Early sex, multiple partners, other STDs
Smoking
HPV infection with high risk subtype
Liquid-based cytology can enhance sensitivity by ≈5%
Start at age 20 or within 3 years first coitus
Cytological Terms
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LGEA = Low grade epithelial abnormality
» Mostly due to HPV
» Also called low grade squamous intraepithelial lesion or LSIL
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HGEA = High grade epithelial abnormality
» Arises from CIN1 & CIN2 (but these are histological terms)
» Also called high grade squamous intraepithelial lesion or HSIL
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Both the above have “Possible” variants
» That is “Possible LGEA” and “Possible HGEA”
Colposcopy
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Limited by need for expert and equipment
Relatively expensive
Subjective
Limited to visible part of the Cx
CIN can be masked by HPV
Of most use in identifying area for biopsy
Better therefore than previous alternative of cone
biopsy
Histology
The gold standard for diagnosis
 Only as good as the sample received
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(except for cone or LLETZ)
And still somewhat subjective
 But accuracy is increased if stains for high
risk HPV DNA is used
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Natural History of CIN
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Progression 123cancer is not inevitable
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CIN 1 - 85% spontaneously regress
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CIN 3 – 50% regress or stay the same
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Progression time varies
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6m to 16 years
But some will have invasive Ca when Pap smear
reports only LGEA
HPV Subtyping
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90% of Ca Cx is associated with High Risk HPV
» Subtypes 16,18,45,31,33,35,52,58 etc
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Highly sensitive for the detection of HGEA
Does not require equipment or expertise
Equivocal results can occur
Of most use in the follow up of treated CIN
And those patients with persisting LGEA on Pap
smear
Treatment Options for CIN
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Observation
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Targeted destruction
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Laser
Diathermy
Cryotherapy
Excision of the Squamocolumnar Junction
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LGEA
Young women
Obvious HPV infection
Chronic LGEA with Low risk HPV subtype
LETZ
Cone Biopsy
Hysterectomy
Follow up of CIN
90 – 95% will be “cured” forever
 Pap smears
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» Repeated until negative
» 12 monthly for 2 years
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Colposcopy
» Ideally at least once 6m after the procedure
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HPV High Risk subtyping
» Perform 12m and 24m after the procedure
» High negative predictive value
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Obstetric implications of treated CIN
debatable
Current NH&MRC Guidelines
Repeat Pap once 12m after the first or if no
tests for 5 years. Thereafter 2 yearly
 Unsatisfactory Pap
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» Treat as required
» Repeat in 3m
» Send for colposcopy if 3 consecutive unsatisfactory
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For LGEA
» If <30 years repeat in 12 months
» If >30 refer for colposcopy or repeat in 6m
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For HGEA
» Send for colposcopy
Prevention of CIN and Genital Warts
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Polyvalent vaccines (types 6,11, 16 & 18)
» Provide 90 – 100% protection from persistent
infection, 16/18-related CIN2-3, adenoCa in situ and
Ca Cx
» Also protects against genital warts caused by the
low risk HPV subtypes 6 & 11
Therapeutic vaccines also under study
 Optimal age for immunisation and need for
boosters under evaluation
 Male immunisation has started
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Counselling a Patient with a Positive
Pap Smear
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This is not cancer
» It is pre cancer
» It is the whole point of doing Pap tests i.e. to detect and
treat pre cancer so as to prevent it becoming cancer
» Just like watching /removing “moles” of the skin
» Not all pre cancer becomes cancer
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It is a common condition
» 40 – 50% of ♀ not immunised at some time in their life
» STD basis not helpful but may need to be addressed
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The Pap test is not diagnostic
» Only a well-directed biopsy can be used for Rx
decisions
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