Natural History of Cervical Cancer
An understanding of the natural history of cervical cancer is helpful in planning, implementing, and evaluating a cervical cancer prevention program in low resource settings. A primary prevention approach to cervical cancer presents greater challenges than other STIs, which can be prevented through safe sex practices such as regular use of condoms. Although male and female condoms offer some protection, skin-to-skin contact still allows for infection with HPV. An effective vaccine could protect women from the most common cancer-producing HPV types. However, types may vary by geographic region, and the degree of oncogenicity of various types remains unclear. Even if effective multivalent vaccines become available to protect women from the major oncogenic types of HPV, vaccination programs may be cost prohibitive and yield delayed benefits only after 20 to 30 years of prophylactic vaccination.
It is not unusual for several types of HPV to cause precursor lesions of the cervix, which we refer to as CIN. The CIN is epithelial cellular change, where the ratio of the cell nucleus to the size of the cell is increased; CIN is graded as CIN I (mild), CIN II (moderate), or CIN III (severe). CIN usually occurs in the transformation zone of the cervix near the squamocolumnar junction where the columnar epithelium of the endocervix and the squamous epithelium of the ectocervix meet. The transformation zone is the critical area to sample when performing cytology collection or to observe during a visual screening procedure. Figure 1 shows the transformation zone.
Transformation zone of the cervix. Used with permission from Program for Appropriate Technology in Health (PATH). Seattle, WA: PATH.
Early cervical cancer prevention programs were based on the premise that cervical disease develops from precursor lesions, which progress from mild to moderate to severe CIN and then to cancer. It appears that CIN progresses to cancer over a prolonged period of time, usually 7 to 20 years and is asymptomatic.[9,14] It can only be detected by a test. It is important that any moderate or severe CIN is treated, because a sizeable proportion may progress to cancer. Mild CIN may spontaneously regress or persist, especially in young women, although among these women progression to a higher grade is less common.[9,14] Therefore, if resources permit, the woman's condition may be monitored, rather than treated.[9,13] Table 2 summarizes the natural history of cervical cancer and outlines possible prevention and management guidelines.[4,9]
J Midwifery Womens Health. 2004;49(4) © 2004 Elsevier Science, Inc.
Cite this: Cervical Cancer Screening in Low Resource Settings: Using Visual Inspection With Acetic Acid - Medscape - Jul 01, 2004.