What is cervical cancer screening?
Cervical cancer screening is an essential part of a woman’s routine health care. Nearly all cases of cervical cancer are caused by infection with sexually transmitted oncogenic, or high-risk, types of human papillomavirus, or HPV. The primary goal of screening is to identify precancerous lesions caused by HPV so they can be removed to prevent invasive cancers from developing. A secondary goal is to find cervical cancers at an early stage, when they can usually be treated successfully. Routine cervical screening has been shown to greatly reduce both the number of cervical cancer cases and deaths from the disease.
For many years, cytology-based screening, known as the Pap test or Pap smear, was the only method of screening. Its use reduced cervical cancer incidence and deaths in countries where screening is common.
However, with the advent of the ability to test for HPV, cervical cancer screening now includes three approaches: HPV testing, which looks for the presence of high-risk HPV types in cervical cells; Pap testing; and HPV/Pap cotesting, which checks the same cell sample for both high-risk HPV types and cervical cell changes.
How is cervical cancer screening done?
When should a woman begin cervical cancer screening, and how often should she be screened?
- Women ages 21 through 29 should be screened with a Pap test every 3 years
- Women ages 30 through 65 should be screened with any of three tests:
- every 5 years with high-risk HPV testing alone
- every 5 years with Pap and high-risk HPV cotesting
- every 3 years with a Pap test alone
- Screening for cervical cancer is not recommended for:
- women younger than 21 years
- women older than 65 years who have had adequate prior screening, with normal results, and who are not otherwise at high risk for cervical cancer
- women who have had a total hysterectomy (surgery to remove the uterus and cervix) and have no history of high-grade cervical lesions or cervical cancer
The screening intervals in the 2018 guidelines reflect scientists’ evolving understanding of the natural history of HPV infection and cervical cancer. Although HPV infection of the cervix is very common, most infections will be controlled by the immune system over the course of 1 to 2 years. Because most HPV infections are transient and produce only temporary changes in cervical cells, overly frequent screening could detect HPV infections or cell changes that would never cause cancer. Treating abnormalities that would have gone away on their own can cause needless psychological stress. Follow-up tests and treatments can also be uncomfortable, and the removal of cervical tissue has the potential to weaken the cervix and may affect fertility or slightly increase the rate of premature delivery, depending on how much tissue is removed.
These screening intervals also limit false-negative results that would delay the diagnosis and treatment of a precancerous condition or cancer. With these intervals, if an HPV infection or cell changes are missed at one screening exam, chances are good that those changes will be detected at the next one, when they can still be treated successfully.
The success of cervical cancer screening is due, in part, to the repeat testing that women typically undergo over many years. A study of a large population of women receiving routine screening showed that women with a history of negative HPV/Pap cotest results have a very low risk of developing precancer or cancer even if a subsequent screening test reveals a new HPV infection or abnormal cervical cells.