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Monday, February 17, 2020

Cervical cancer Screening

Dr. A K Nanda          
MD, Radiation Oncology


What is screening?


  • Screening is checking for disease when there are no symptoms. That is, screening is a test done in normal individuals to search for diseases.
  • As screening may find diseases at an early stage, there may be a better chance of curing the disease.

Need for Cervical cancer screening


  • To know this first we have to understand what CIN is. Cervical Intraepithelial Neoplasia (CIN) is a precancerous condition in which abnormal cells grow on the surface of the cervix which may later converts to cancer. It is classified as 3 grades CIN1, CIN2 and CIN3.
  • It is important to know that, CIN does not usually cause any symptoms. Abnormal cells are found only after a routine Pap smear.
  • Most people with CIN do not develop cancer. If cancer does form, it takes years to develop. This long transit time between precancerous lesion to development of cancer gives doctors time to find and remove problem areas.
  • Hence if we do regular cervical cancer screening, we can get cervical lesions in precancerous stage and will be easily treatable.

Two types of  screening tests for Cervical cancer

  1. Papanicolaou test (Pap test or Pap Smear):- A Pap test is a procedure done in a hospital in which cells are taken from the cervix and looked it under a microscope. It is most often done during a routine pelvic examination.
  2. HPV test:- The HPV test looks for the high-risk types of Human Papilloma virus(HPV) that cause most cases of cervical cancer.

Cervical Cancer Screening Recommendations


  1. Cervical cancer screening should be started at the age of 21 years 
  2. Pap test every three years between 21 and 29 years old
  3. Pap test and HPV test (co-testing) every five years between 30 and 65 years old or a Pap test every three years.

Screening for age <21 years

  • Women < 21 years should not be screened even if the woman is sexually active.
  • This is because the incidence of cervical cancer at the age <21 is very less.
  • Again cervical cancers, those occurring in women in their teens and early 20s are more rapidly progressive i.e. a very less time gap between precancerous lesion and cancer. Hence these may not be preventable through feasible screening strategies.

Screening for ages 21-29 years

  • Cervical cancer screening should be started at the age of 21 years.
  • Pap smear is done alone every 3 years.
  • HPV testing should not be done for screening in this age group.

Why HPV testing is not done in this age group?

The prevalence of HPV in women aged younger than 30 years is high. Most of the HPV infections resolve itself without any interventions within one year. Hence if these women are screened for HPV, most women will go for further unnecessary investigations who are not going to develop cancer.

What to do if a female is virgin?

  • If a female is virgin, meaning she didn't have sexual (vaginal) intercourse, she may have a low risk of cervical cancer, but she can be still considered for screening.
  • In most cases, cervical cancer is caused by HPV. If a female have never had any type of sexual intercourse, she is unlikely to have HPV. However, there are other risk factors for developing cervical cancer, such as family history and smoking.
  • Hence Discuss with your doctor when to begin cervical cancer screening . Together you and your doctor can decide what's best for your particular situation.

Screening for age 30-64 years

  • These women should be screened with both Pap smear and HPV testing every 5 years.
  • In sites where HPV testing is not available either due to financial or logistical issues Pap smear alone is acceptable but in every 3 years.
  • Women who may no longer be having sex or who may feel too old to have a child should still have to go through regular cervical cancer screening.

Screening for age >65 years

  • Screening should be stopped at the age of 65 years for women with adequate negative prior screening i.e. either 3 consecutive Pap smear negative or 2 consecutive HPV test negative.
  • Screening should not be resumed for any reason, even if a women reports having a new sexual partner.

Why should we stop screening at age >65 years?

  • Incidence of HPV infection is low in this age group and if infection occurs it is unlikely that it will cause cancer within remaining life time.
  • Again precancerous lesion is rare after the age of 65 years. Most of the abnormal screening tests in this age is false positive and do not reflect precancerous condition.

Results

If both Pap smear and HPV negative

Continue screening as per age specific guidelines

If Pap smear positive irrespective of HPV status

Patient is referred for Colposcopy ( Colposcopy is a procedure to closely examine cervix, vagina and vulva for signs of disease using a special instrument called colposcope)

 If HPV positive and Pap smear negative


This screening strategy is not applied to special population like


  1. History of cervical cancer
  2. Who were exposed in utero to diethylstilbestrol (DES) -- (In past DES was widely used for a variety of indications, including pregnancy support for women with history of recurrent miscarriage, hormone therapy for menopausal symptoms and estrogen deficiency in women)
  3. Who are immunocompromised (eg. infection with HIV)

Screening in women undergone hysterectomy with removal of cervix

  • If there is no history of precancerous lesion and removal of uterus along with cervix is done due to benign reasons, there is no need for screening in these population.
  • This is because risk of Pap abnormality after hysterectomy is very less.

HPV vaccinated women

Vaccination with HPV vaccine does not alter screening strategies. For more about HPV vaccine please go to previous article, “A vaccine in childhood can prevent a cancer in adulthood”.

Reference

  • Am J Clin Pathol 2012;137:516-542. Available at: https://doi.org/10.1309/AJCPTGD94EVRSJCG
  • J Low Genit Tract Dis 2013;17(5 Suppl 1):S1-S27. Available at: http://www.asccp.org/

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