Benefits and harms of screening

Benefits of participating in cervical cancer screening

International studies have shown that three-yearly screening can reduce the life-time risk of cervical cancer with more than 80%.(1)  A single Pap test can reduce the risk of cervical cancer during the next 5 years by 50%.(2) As no screening test can be 100% effective, there will always be some cases that occur despite adequate screening. However, women who develop cervical cancer despite regular screening participation, have a lower mortality of the disease, mainly because the disease will usually be detected at an earlier stage.(3)

Harms of participation

The screening test itself can be mildly uncomfortable, and will require you to put aside time for seeing a doctor.

Around 5 out of 100 Pap tests show cell changes, and 2 of these are so clear that a referral to a gynaecologist for diagnostic work-up is warranted.  The remaining 3 will contain unclear changes that will have to be followed up with an additional Pap test after 6-12 months. A large proportion of the unclear changes will have spontaneously resolved by the time of the repeat test. Waiting for diagnostic work-up or follow-up tests can cause anxiety in some women.

The diagnostic work-up of clearly positive screening tests include visual inspection of the cervix (colposcopy) and biopsies of the areas of the cervical mucous membrane that show cell changes. The biopsies can cause some bleeding, cause discomfort and also mild pain.

About half of those with diagnostic work-up, or 1 out of 100 women with screening tests, will have a precancerous lesion requiring treatments. The treatment is the removal of the abnormal tissue at the surface of the cervix (conisation). Vaginal bleeding is usual for a week after the procedure. Studies have shown an increased risk for premature births and late abortions among women who have undergone treatment for precancerous lesions of the cervix. The extra risk of prematurity is somewhere between 2-11 births out of every 100 births by women who have been treated for precancerous lesions of the cervix.(4,5) About one third of the precancerous lesions would progress to cervical cancer without treatment.(6)

 

1.         IARC. Screening for squamous cervical cancer: duration of low risk after negative results of cervical cytology and its implication for screening policies. IARC Working Group on evaluation of cervical cancer screening programmes. Br Med J (Clin Res ed) 1986;293:659-64.

2.         Lönnberg S, Ahti Anttila, Luostarinen T, Nieminen P. Age-specific effectiveness of the Finnish cervical cancer screening programme. Cancer Epidemiol Biomarkers Prev 2012;21:1354-61.

3.         Andrae B, Andersson TM, Lambert PC, Kemetli L, Silfverdal L, Strander B, Ryd W, Dillner J, Törnberg S and Sparén P. Screening and cervical cancer cure: population based cohort study. BMJ 2012;344:e900.

4.        Castañon A, Brocklehurst P, Evans H, Peebles D, Singh N, Walker P, Patnick J and Sasieni P for the PaCT Study Group. Risk of preterm birth after treatment for cervical intraepithelial neoplasia among women attending colposcopy in England: retrospective-prospective cohort study. BMJ 2102;345:e5174.

5.        Albrechtsen S, Rasmussen S, Thoresen S, Irgens LM and Iversen OE. Pregnancy outcome in women before and after conisation: population based cohort study. BMJ 2008;337:a1343.

6.       McCredie MRE, Sharples KJ, Paul C, Baranyai J, Medley G, Jones RW and Skegg DCG. Natural history of cervical neoplasia and risk of invasive cancer in women with with cervical intraepithelial neoplasia 3: a retrospective cohort study. Lancet Oncol 2008;9:425-34.